Co-reporter:Li Huang, Guangjie Huang, Yunchang Xin, Lingfei Cao, ... Qing Liu
Journal of Materials Science & Technology 2017 Volume 33, Issue 9(Volume 33, Issue 9) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.jmst.2017.03.009
In this work, two different intermediate annealing processes, single-step annealing (SSA, 530 °C/15 h) and two-step annealing (TSA, 450 °C/5 h + 530 °C/15 h), were used to tailor microstructure before cold-rolling and annealing of the final twin-roll cast Al-Mn foils. The recrystallization behavior and mechanical properties during annealing of severely cold-rolled foils were systematically studied. Our results show that discontinuous recrystallization occurs in SSA-foils during annealing at 150–310 °C, in contrast with continuous recrystallization in TSA-foils. The continuous recrystallization develops much finer grains (∼1.35 μm) in the TSA-foils than those by discontinuous recrystallization in the SSA-foils (∼14.7 μm). The texture components in cold-rolled TSA-foils hardly change (retained rolling-textures) after continuous recrystallization, while those in the cold-rolled SSA-foils mainly transform into a strong cube component {001} 〈100〉 after discontinuous recrystallization. Finally, a maximized elongation to fracture of ∼23.9% was achieved in the TSA-foil, much higher than that of the SSA-counterparts, ∼8.3%. The relationships between the microstructure and mechanical properties were discussed.
Co-reporter:Sainan Wu, Bita Ghaffari, Elizabeth Hetrick, Mei Li, Qing Liu, Zhihong Jia
Journal of Materials Processing Technology 2017 Volume 249(Volume 249) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.jmatprotec.2017.06.037
A hardened thermo-mechanically affected zone (TMAZ), measuring a few millimeters in width, was identified between the weld nugget and base metal in AA6111 resistance spot welds (RSW). The spatial distribution, microstructure, hardness and evolution of the TMAZ, and the impact on fracture morphology of spot welds were investigated through micro-hardness mapping, optical metallography, transmission electron microscopy, welding process simulation and quasi-static tensile tests. Strain hardening induced by the compressive force applied by the welding electrodes, as opposed to precipitation hardening induced by heat, was determined to be the dominant hardening mechanism in the development of the TMAZ in AA6111 RSW.Download high-res image (383KB)Download full-size image
Co-reporter:Weijun He, Xin Chen, Na Liu, Baifeng Luan, Gaihuan Yuan, Qing Liu
Journal of Alloys and Compounds 2017 Volume 699(Volume 699) pp:
Publication Date(Web):30 March 2017
DOI:10.1016/j.jallcom.2016.12.300
•Microstructures of Zr-4 alloy after cryorolling and room temperature rolling were characterized.•Mechanism of cryorolling enhanced inhomogeneous rolling deformation was discussed.•Microstructures of Zr-4 samples rolled at different conditions in annealing were identified.•Correlation between rolling condition and recrystallized grain size were explored.This work focuses on the influence of cryo-rolling on subsequent recrystallization of hexagonal Zr-4 alloy. With initial recrystallized microstructure, the as-received Zr-4 sheets were rolled at liquid nitrogen temperature (LNT) and room temperature (RT). For each rolling temperature, two levels of strain, 20% and 40%, were applied. Then, samples, including as-received and rolled sheets, were annealed at 700 °C for 3 min–5 min. Microstructures of the deformed and annealed Zr-4 samples were characterized in detail by electron backscatter diffraction (EBSD) method. After rolling, no twin lamella is observed in Zr-4 sample. It is found that the intensity of the heterogeneous deformation in cryo-rolling is more severe than that in RT-rolling. After annealing, the recrystallized average grain size of Zr-4 decreases with the increases of the applied strain at both deformation temperatures. For a given rolling reduction, the recrystallized average grain size increases with decreasing deformation temperature. The texture orientation of Zr-4 was not remarkably changed during the rolling deformation and annealing process.
Co-reporter:Li Huang, Guangjie Huang, Lingfei Cao, Xiaodong Wu, Zhihong Jia, Mingyong Xia, Qing Liu
Materials Science and Engineering: A 2017 Volume 682() pp:63-72
Publication Date(Web):13 January 2017
DOI:10.1016/j.msea.2016.11.018
A two-step annealing treatment consisting of a pre-recovery process (450 °C/5 h) and a following recrystallization process (530 °C/15 h) was developed for a cold-rolled twin-roll cast 3003 alloy (Al-1.13Mn-0.45Fe-0.1Si in wt%) sheet. The effects of pre-recovery on recrystallization behavior and mechanical properties were systematically studied. Our results show that fine quasi-equiaxed grains together with very weak ND-rotated cube (001) <310> texture was successfully obtained using the proposed two-step annealing treatment. It is found that pre-recovery stimulates the formation of precipitates-free zones around constituent particles. Within such precipitates-free zones, substantial random oriented sub-grains can readily grow to critical size for nucleation, which contribute to enhanced nucleation without preferential orientation. This is the reason for the formation of fine grains as well as a weak texture in the two-step annealed sheet. The sheets that were subject to this two-step annealing also exhibits an extremely weak mechanical anisotropy with a Δr value 0.03, much lower than that of sample (0.31) subjected to a single-step annealing at 530 °C for 15 h.
Co-reporter:Renlong Xin;Maoyin Wang;Zhe Liu;Xingpin Chen;Guangjie Huang
Advanced Engineering Materials 2017 Volume 19(Issue 7) pp:
Publication Date(Web):2017/07/01
DOI:10.1002/adem.201700035
This paper aims to compare the textural effect on the rollability of Mg alloy sheets at different temperatures. Wedge-shaped AZ31 alloy plates with two kinds of initial textures are designed and rolled at five different temperatures. Then, the rollability under different conditions can be evaluated by observing the development of edge-cracks. The results show that the initial texture has little influence on the single-pass rollability at low temperatures (100 and 150 °C), while the influence is significant for rolling above 150 °C. Schmid factor and in-grain misorientation axis analyses revealed that the textural effect on the activation of prismatic glide accounted for the observed distinct rollability at elevated temperatures.
Co-reporter:Rongguang Li, Renlong Xin, Qing Liu, Adrien Chapuis, Shifeng Liu, Guangyan Fu, Lin Zong
Materials & Design 2017 Volume 114(Volume 114) pp:
Publication Date(Web):15 January 2017
DOI:10.1016/j.matdes.2016.10.074
•Grain size, texture and precipitates have much different influences on hardness and proof stress for Mg-Gd alloys.•The 0.2% proof stress of the alloys was largely affected by grain size and texture.•The hardness of the alloys was predominately controlled by the density of precipitates.In this study, an age-hardenable Mg–14Gd–0.5Zr (wt.%) alloy was used as a model material to investigate the effects of grain size, texture and density of precipitates on the hardness and 0.2% proof tensile yield stress. Six kinds of samples with different grain size, texture and density of precipitates were prepared by varying the extrusion process and aging treatment. The microstructure and texture of the samples were examined by electron backscatter diffraction and transmission electron microscope. The examination results indicate that 0.2% proof yield stress of the Mg-Gd alloys were largely affected by the grain size and texture, while the hardness of the alloys was predominately controlled by the density of precipitates. This study reveals that the grain size, texture and density of precipitate can have much different influences on the hardness and 0.2% proof yield stress for the Mg-Gd alloys. It raises an important issue about the mechanical-testing standards and product-design guidelines for the age-hardenable magnesium alloys.Download high-res image (227KB)Download full-size image
Co-reporter:Li Tan, Xiyan Zhang, Qi Sun, Jiangping Yu, Guangjie Huang, Qing Liu
Materials Science and Engineering: A 2017 Volume 699(Volume 699) pp:
Publication Date(Web):24 June 2017
DOI:10.1016/j.msea.2017.05.092
The high cycle fatigue behavior of a hot-rolled AZ31 magnesium alloy were investigated at high frequencies (97.3 Hz) and different stress amplitudes (50 MPa, 60 MPa, 70 MPa, 90 MPa, 110 MPa) by using a tension-compression fatigue test at room temperature. The results show that the stress amplitude significantly influences the activation of fatigue mechanisms. When the stress amplitudes were 50 and 60 MPa, which is close to the fatigue strength, only basal dislocations were observed, no obvious twins and dislocations can be observed. Grains were refined under high cyclic numbers led by continuous dynamic recrystallization (CDRX). When the stress amplitudes increased to 70, 90 and 110 MPa, which were higher than the fatigue strength, few {10–12} tensile twins, {10–11}-{10–12} double twins and pyramidal dislocations were observed in the fatigued samples, and no obvious grain refinement was observed, only a small amount of twins in the material. Pyramidal slip is one of the deformation mechanisms in magnesium alloy during high cycle fatigue deformation when the stress amplitude is higher than the fatigue strength.
Co-reporter:X.P. Chen, Y.P. Xu, P. Ren, W.J. Li, W.Q. Cao, Q. Liu
Materials Science and Engineering: A 2017 Volume 703(Volume 703) pp:
Publication Date(Web):4 August 2017
DOI:10.1016/j.msea.2017.07.055
Aging treatments under three temperatures were performed to investigate the aging hardening response of high carbon high manganese austenitic Fe-30Mn-10Al-2C steel. The dramatic differences in hardness and microstructure were observed after aging under different temperatures. The aging treated at 500 ℃ had a typical aging hardness curve and the hardening response originated from the precipitation of κ-carbide, which plays an important role in performance improvement. When aging was conducted at 700 ℃, there was no significant change in hardness because a balance between aging hardening and high-temperature softening was built. On the contrary, the aging under 600 ℃ exhibited novel continuous increase in hardness and dramatic secondary hardening due to the formation of β-Mn which had an intrinsic high hardness. In addition, the β-Mn was also found after aging for long time under other temperatures. Unfortunately, the formation of β-Mn distributed along γ grain boundaries led to serious brittle fracture. For further investigation and application, the β-Mn transformation behavior was discussed based on the diffusion and redistribution of elements. Considering the dramatic difference in the formation kinetics of β-Mn depending on aging temperature, the diagram of β-Mn transformation was achieved to obtain optimized aging conditions.
Co-reporter:Yannan Wang, Yunchang Xin, Qing Liu
Journal of Alloys and Compounds 2016 Volume 666() pp:341-345
Publication Date(Web):5 May 2016
DOI:10.1016/j.jallcom.2015.12.253
•Annealing removes the double peaks of basal poles tilting from the ND toward the TD.•A concentration of basal poles toward the ND occurs after a complete recrystallization.•There is a higher nucleation rate of basal orientations than that of off-basal orientation during annealing.In the present study, a Mg–5.7Zn hot rolled plate was annealed at different temperature, with the aim to study the texture evolution during static recrystallization. Our results show that the initial basal texture with two peaks of basal poles tilting from the normal direction (ND) toward the transverse direction (TD) is replaced by a single peaked basal texture and basal poles concentrate toward the ND after a complete recyrstallization. It is found that the recrystallized grains mainly appear in the shear bands containing many twins. The recrystallized grains with basal pole close to ND have much higher nucleation rate than nucleus randomly oriented and grain growth does not change the advantage of basal orientations, which is mainly responsible for the concentration of basal poles toward the ND.
Co-reporter:B.F. Luan, J.M. Wang, R.S. Qiu, B.R. Tao, W.J. He, X.Y. Zhang, R.P. Liu, Q. Liu
Journal of Alloys and Compounds 2016 Volume 678() pp:456-462
Publication Date(Web):5 September 2016
DOI:10.1016/j.jallcom.2016.03.198
•Clarified the distribution trends of Fe>Mo>Bi in precipitates by STEM-EDS.•Verified the experimental results by first-principles calculation.•Predicted the site preferences of alloying elements by first-principles calculation.•Hybridization and pseudogap lead to the strong distribution and site preferences.Energy dispersive X-ray spectroscopy in scanning transmission electron microscope (STEM-EDS) technique and first-principles calculation are jointly utilized to investigate the distribution trends and site preferences of alloying elements in the precipitates within Zr-1.0Cr-0.4Fe-0.4Mo-0.4Bi alloy. Based on selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDS) results, the precipitates within the studied alloy are confirmed to be ZrCr2-based Laves phase with FCC (C15) type structure. The STEM-EDS elemental mapping is acquired to clarify the distribution trends of alloying elements in precipitates, i.e. Fe>Mo>Bi. To better verify this distribution behavior, substitutional formation energies and equilibrium concentrations of ternary alloying elements in ZrCr2 Laves phase are calculated by first-principles. The calculated results show a good consistence with the STEM-EDS results. In addition, the site preferences of ternary alloying elements in ZrCr2 Laves phase are predicted by the calculation of transfer energies. Finally, the reasons accounting for different distribution trends and site preferences of alloying elements in ZrCr2 Laves phase are discussed in terms of density of states, which attributed to the pseudogap effect and hybridizations between atoms.
Co-reporter:Fuhui Li, Xiaozhi Wu, Rui Wang, Weiguo Li, Qing Liu
Computational Materials Science 2016 Volume 114() pp:1-12
Publication Date(Web):March 2016
DOI:10.1016/j.commatsci.2015.12.003
The transformation pathways between vitual long period stacking-ordered Mg are investigated using first-principles methods. Two kinds of slip modes, multi-slip-planes mode (M mode) and single-slip-plane mode (S mode), are proposed to calculated the generalized stacking fault energy curves during the transformation process. Based on the energy barriers, the optimized transformation pathways can be obtained. The energy barriers of M mode and S mode are the same for 2H →→ 6H2, 6H1 →→ 6H2, 14H4 →→ 14H2 and 14H4 →→ 14H5, respectively. However, the energy barriers of M mode are larger than that of S mode for these transformation with the consideration of vacuum space. For 2H →→ 6H1 and 14H1 →→ 14H3, the energy barriers of M mode are smaller than that of S mode. The energy barriers of M mode are larger than that of S mode for 18R1 →→ 18R2 and 14H2 →→ 14H5. It is found that the energy barriers increase with the increasing of the numbers of AA stacking of the different slip modes.
Co-reporter:X.P. Chen, H.F. Sun, D. Chen, L.X. Wang, Q. Liu
Materials Characterization 2016 Volume 121() pp:149-156
Publication Date(Web):November 2016
DOI:10.1016/j.matchar.2016.10.006
•Effects of Cu content on texture and magnetic properties have been investigated.•High temperature annealing results in a sharp cube texture with few annealing twin.•The increase of Cu content can reduce the saturation magnetization in Cu-Ni alloys.The crystallographic texture, micro-hardness and magnetic property have been investigated in Cu-57 at.% Ni, Cu-53 at.% Ni, and Cu-49 at.% Ni alloy used as substrates for coated conductors. In this work, a similar rolling texture was observed in the cold rolled condition for the three alloys. For each material, annealing at higher temperature results in a much stronger cube texture but the fraction of annealing twin boundary was quiet low. When annealing at 700 °C and 800 °C, it was presumed that the increase of Cu element increased grain boundary mobility, which then lead to the enhancement of twin boundary and weakened the cube texture. In addition, magnetization measurements indicate that the increase of Cu content can effectively reduce the saturation magnetization in Cu-Ni alloys. The comparatively low ferromagnetism for both Cu-53 at.% Ni and Cu-49 at.% Ni alloys suggests that substrates produced using these materials will benefit from decreasing hysteresis losses for alternating current applications.
Co-reporter:Mingyu Wu, Renlong Xin, Ying Wang, Yang Zhou, Ke Wang, Qing Liu
Materials Science and Engineering: A 2016 Volume 677() pp:50-57
Publication Date(Web):20 November 2016
DOI:10.1016/j.msea.2016.09.030
Electron beam welding (EBW) is a fusion joining process particularly suitable for the welding of thick titanium plates. In the present work, commercial high-purity titanium plates with a thickness of 30 mm were welded by EBW. Color metallography and electron backscattered diffraction (EBSD) were used to investigate the microstructure and texture after welding. The results show that the grains become elongated or coarsened in the weld zone (including the fusion zone and the heat-affected zone). Meanwhile, as revealed by the (0001) pole figures, the texture of the weld zone is enhanced. Despite the grain coarsening, the welded plates exhibit higher yield strength than the base metal. A Schmid factor analysis revealed that this increase in yield strength could be attributed to texture strengthening. Specifically, the grains in the weld zone are re-oriented. For the weld zone, the Schmid factor is relatively small for prismatic slip, which is the most easily activated deformation mode for titanium at room temperature. Compared to the base metal, the Schmid factors for {101¯2} twinning and {112¯2} twinning are larger for the weld zone. The EBSD observations confirmed that a large number of {101¯2} twins and {112¯2} twins are formed in the weld zone during tension. However, the plastic strain caused by the twin formation is much smaller than that caused by the prismatic slip in the base metal. As a result, necking occurred in the base metal during the transverse tensile tests.
Co-reporter:Yunchang Xin, Liangchen Lv, Houwen Chen, Cong He, Huihui Yu, Qing Liu
Materials Science and Engineering: A 2016 Volume 662() pp:95-99
Publication Date(Web):26 April 2016
DOI:10.1016/j.msea.2016.03.061
The effect of interaction between {101̅2} twin boundaries (TBs) and 〈a〉 dislocations on deformation behavior of TBs migration process was studied. This TB-dislocation interaction greatly enhances activation stress for TB motion and retards TB migration during reloading. Interestingly, a severe TB-dislocation interaction improves strain hardening at the early stage, while reduces the peak hardening rate at the latter stage. High resolution transmission electron microscopy results indicate that severe TB-dislocation interaction greatly damages the coherence of TBs and might induce curving of TBs. Migration of the TBs that intensively interact with dislocations leaves behind low angle boundaries at the initial TBs.
Co-reporter:Shiwei Pan, Yunchang Xin, Guangjie Huang, Qi Li, Feilong Guo, Qing Liu
Materials Science and Engineering: A 2016 Volume 653() pp:93-98
Publication Date(Web):20 January 2016
DOI:10.1016/j.msea.2015.12.002
The influence of rolling path on texture and mechanical anisotropy of a Mg–2Zn–2Gd plate was investigated. The initial TD-split texture remains after rolling along RD and annealing at 450 °C for 1 h, whereas, after rolling along TD and annealing, changes into a RD-split one. TD, RD, and ND represent transverse direction, rolling direction and normal direction of the initial plate, respectively. Rolling path determines orientations of the recrystallized grains. The nuclei of recrystallized grains with basal poles distribution along the TD have a clear advantage over the ones along the RD in the RD-rolled and plates and vice-versa. This is the reason for formation of RD (TD)-split texture in the TD (RD)-rolled and annealed plate. A cross rolling alternately along TD and RD followed by annealing develops a texture with basal poles evenly distributing on a circle about 40° away from ND. This cross rolled plate exhibits a completely removed planar mechanical anisotropy.
Co-reporter:Qunying Yang, Zanhui Deng, Zhiqing Zhang, Qing Liu, Zhihong Jia, Guangjie Huang
Materials Science and Engineering: A 2016 Volume 662() pp:204-213
Publication Date(Web):26 April 2016
DOI:10.1016/j.msea.2016.03.027
The flow behavior, microstructure evolution and softening mechanism of an AA7085 aluminum alloy are investigated by isothermal hot compression tests at 450 °C with the strain rates of 0.001 s−1 and 0.1 s−1. Optical microscopy (OM), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) are used to characterize microstructure evolution during deformation. The results reveal that the flow stress curves exhibit a single peak and then two types of flow stress curves are found in the present study. Microstructure characterization reveals that dynamic recovery (DRV) and recrystallization (DRX) occur in the both conditions. The microstructure discrepancy becomes significant with increasing strain rate after a certain strain level (ε≥0.3). In the case of 0.001 s−1, the dynamic recovery is thought to precede continuous dynamic recrystallization. As the strain rate increased, the absence of dynamic recovery provides enough stored energy for discontinuous dynamic recrystallization (DDRX), resulting in a retardation in the occurrence of continuous dynamic recrystallization (CDRX).
Co-reporter:Dejia Liu, Renlong Xin, Yu Hongni, Zhe Liu, Xuan Zheng, Qing Liu
Materials Science and Engineering: A 2016 Volume 658() pp:229-237
Publication Date(Web):21 March 2016
DOI:10.1016/j.msea.2016.01.098
In the present study, an Mg weld with β-type fiber texture was produced by friction stir welding (FSW) and then was subjected to tension and compression along the transverse direction (TD). The deformed microstructure by 5% strain was examined in various regions of the Mg weld by electron backscatter diffraction (EBSD) technique. It was found that profuse twinning was activated in stir zone (SZ) -side after tension and in SZ-center and crown zone (CZ) -center after compression due to the presence of relatively large Schmid factor (SF). However, a few twins (2–3%) were also observed in SZ-center after tension and in SZ-side after compression. In this case, the twins have very small and even negative SF. For the twins with large SF, they were likely connected at grain boundaries forming twin pairs, while for those with small or negative SF, they were mostly confined within grains. For connected twins, most of the active variants have favorable SF and geometric compatibility factor (m′). However, the distributions of SF and m′ are different between the twins formed in compression and tension. For isolated twins, the adjacent grains connected with the twins were generally in favorable orientation for basal slip, and the selection of twin variants was likely affected by m′ between the most favorable basal slip and the twins.
Co-reporter:L.X. Wang, X.P. Chen, D. Chen, H.F. Sun, Q. Liu
Materials Science and Engineering: A 2016 Volume 676() pp:48-55
Publication Date(Web):31 October 2016
DOI:10.1016/j.msea.2016.08.092
The influence of preferential orientation (namely cube texture) on annealing twins in a cold rolled (95% thickness reduction) pure nickel has been investigated during isothermal annealing at low temperature. The results reveal that the cube oriented grains in cube related twinning (CT) regions have larger average boundary migration rate in comparison with grains in non-cube related twinning (NCT) regions. However, the twin density is always lower in CT regions than that in NCT regions. This is contrary to the growth accident model that suggests that twin density was proportional to the grain boundary velocity and grain boundary distance. It can be interpreted by the fact of the selective nucleation and growth mechanism for cube oriented grains which are less dependent on annealing twinning during recrystallization. Furthermore, during grain growth the average length of annealing twin boundary segments has a significant increment, which is probably attributed to lengthening of low energy twin boundaries along with the migration of other neighboring boundaries.
Co-reporter:X.P. Chen, L. Mei, D. Chen, Z.L. Bao, Q. Liu
Materials Science and Engineering: A 2016 Volume 667() pp:311-316
Publication Date(Web):14 June 2016
DOI:10.1016/j.msea.2016.04.099
The effect of pre-aging and peak-aging treatments prior to cryorolling on the microstructure and mechanical properties of 6016 Al alloys were investigated by hardness measurements, tensile tests, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results showed that high density of dislocation was induced by cryorolling with 80% thickness reduction. The pre-aging treatment enabled the alloy to have stronger work hardening effect during cryorolling and higher precipitation potential during subsequent aging than the peak-aging treatment. This was due to that the pre-aging enhanced the dislocations accumulating in the cryorolling of pre-aged specimen, and promoted the secondary precipitation during subsequent aging after cryorolling. Meanwhile, the yield strength and ultimate tensile strength of the pre-aged specimen subjected to cryorolling and subsequent aging significantly increased by 72% and 50%, respectively, while the ductility remained similar, as compared to the conventional peak-aged specimen.
Co-reporter:Lili Liu, Xiaozhi Wu, Rui Wang, Weiguo Li, Qing Liu
Computational Materials Science 2015 Volume 103() pp:116-125
Publication Date(Web):1 June 2015
DOI:10.1016/j.commatsci.2015.03.024
The elastic constants, generalized stacking fault energies, and surface energies of NiAl and FeAl have been investigated by using the first principles methods combined with a quasiharmonic approach. Pugh ratio, Cauchy pressure, elasticity anisotropy and Rice ratio are presented at different temperature. It is interesting to find that the anisotropy of NiAl decreases with increasing temperature, but FeAl increases. NiAl has better ductility than FeAl according to the Pugh ratio and the Cauchy pressure. However, the Rice ratio shows the opposite result. Furthermore, the dislocation core structure of NiAl and FeAl is also presented based on an improved Peierls–Nabarro theory.
Co-reporter:JinYi Yao;BingShu Wang;LiPing Deng
Science China Technological Sciences 2015 Volume 58( Issue 12) pp:2052-2059
Publication Date(Web):2015 December
DOI:10.1007/s11431-015-5937-6
The effects of starting texture on he flow curves, and microstructure and texture evolutions of AZ31 (Mg-3Al-1Zn-0.3Mn in wt.%) alloy during uniaxial compression at room temperature have been investigated by experiments and simulations. Two kinds of cylindrical compression samples were cut from the AZ31 extruded rod: one was cut with the compression direction parallel to the extruded direction (ED), and the other was cut with the compression axis perpendicular to the ED. The samples were termed as C//ED sample and C⊥ED sample, respectively. The results indicate that the general characteristics of flow curves and texture evolutions in both C⊥ED and C//ED samples during compression can be well explained by the relative activities of deformation mechanisms, which show a strong orientation dependence on the initial textures and the current texture. A significant yield behavior can be induced by {10-12} twinning at the starting deformation, and the lower yield stress in C⊥ ED sample can be enhanced by the high activity of basal
slip. The work hardening behavior is related to the activities of basal slip, pyramidal slip, {10-12} twinning, as well as {10-11} twinning. However, the activity of prismatic slip is insensitive to the starting texture, and mostly negligible in all samples.
Co-reporter:Hai Hu, Xiaozhi Wu, Rui Wang, Weiguo Li, Qing Liu
Intermetallics 2015 Volume 67() pp:26-34
Publication Date(Web):December 2015
DOI:10.1016/j.intermet.2015.07.008
•The phase stability and mechanical properties of C11b and C40 MoSi2 with alloying elements Al, Mg and Ge were investigated.•There is a phase transition from C11b to C40 when the concentrations of Al and Mg reach ∼7 at% and ∼6 at.%, respectively.•The ductility (hardness) will be enhanced (reduced) by increasing the concentrations of Al or Mg. Ge have a reverse effects.•The density of states is used to analysis the effects of alloying elements on the mechanical properties.The phase stability, mechanical properties and electronic structure of C11b and C40 MoSi2 with alloying elements Al, Mg and Ge were systematically investigated using first principles methods. The calculated lattice constants and elastic constants of C11b and C40 MoSi2 are in good agreement with the previous results. It is found that there is a phase transition from C11b to C40 when the concentrations of Al and Mg reach ∼7 at.% and ∼6 at.%, respectively. Based on the elastic constants, the anisotropy, ductility, hardness and melting temperatures are presented for MoSi2 with alloying elements. For C11b, the ductility will be enhanced by increasing the concentrations of Al or Mg. Simultaneously, hardness will be reduced by the increasing of Al or Mg. Ge have a reverse effects. For C40, the ductility is reduced weakly by Al or Mg. In addition, the effects of substitution of Mo by Nb with Si substitution of Si by Al, Mg and Ge are also investigated. Nb and Mg codoping can improve the ductility of MoSi2. Finally, the density of states is used to analysis the effects of alloying elements on the mechanical properties, and the results are in consistent with the predictions based on elastic constants.
Co-reporter:Ning Guo;Bo Song;Bing-Shu Wang
Acta Metallurgica Sinica (English Letters) 2015 Volume 28( Issue 6) pp:707-714
Publication Date(Web):2015 June
DOI:10.1007/s40195-015-0251-7
The influence of torsion deformation on textures of cold drawing pearlitic steel wires was investigated by twisting the wires to different number of revolutions. Macro-texture (over the entire wire cross section) associated with torsion deformation was investigated by X-ray diffraction, while micro-texture (near the wire surface) was characterized by EBSD. The results show that the \( \left\langle { 1 10} \right\rangle \) macro-texture increases at the beginning of torsion and then decreases with increasing of torsion strain, while the \( \left\langle { 1 10} \right\rangle \) micro-texture decreases linearly with increasing of torsion strain. The relationships between the \( \left\langle { 1 10} \right\rangle \) fiber texture and the microhardness of the wires are also discussed.
Co-reporter:Yunchang Xin, Yuanyuan Zhang, Huihui Yu, Houwen Chen, Qing Liu
Materials Science and Engineering: A 2015 Volume 644() pp:365-373
Publication Date(Web):17 September 2015
DOI:10.1016/j.msea.2015.07.049
In the present study, a comparative study about the hardening effect of solute segregation at {101¯2} twin boundaries (TBs) on a {101¯2} twinning predominant deformation and a detwinning predominant one was carried out. The influence of the pre-straining and subsequent annealing conditions on mechanical behavior was systematically addressed. Our results show that solute segregation at TBs can occur even at 100 °C. The annealing at 100 °C for 20 min induces a partial segregation at TBs, while that at 150 °C or higher temperature for 20 min can induce a complete solute segregation. The annealing conditions and pre-strain levels generate quite different effects on deformation by twinning and that by detwinning. Both annealing hardening and annealing softening might happen during the twinning predominant recompression. Annealing hardening occurs only with pre-strains of 3.0% and 5.5% after annealing at 100 °C for 6 h. A higher pre-strain or a higher annealing temperature or a longer annealing time generate a higher annealing softening effect. However, during the detwinning predominant recompression, all used annealing treatments generate hardening effect in all the pre-strained samples. With a complete solute segregation at TBs, a hardening of about 11–25 MPa is generally achieved. It is also found that solute segregation at TBs reduces the strain hardening rate of deformation by TBs migration.
Co-reporter:Renlong Xin, Changfa Guo, Zeren Xu, Guodong Liu, Xiaoxu Huang, Qing Liu
Scripta Materialia 2014 Volume 74() pp:96-99
Publication Date(Web):March 2014
DOI:10.1016/j.scriptamat.2013.11.008
Sheet rolling was performed at room temperature on a friction-stir-welded Mg alloy. Long twin bands comprising small {10-12}<-1011> twins (average size ∼7 μm) were revealed. Based on the long twin bands identified, the grain boundary disorientation and strain accommodation between neighboring twins and global Schmid factors were assessed. The results indicate that these factors are favorable for the formation of such long twin bands in the applied rolling deformation.
Co-reporter:Ning Guo, Baifeng Luan, Fangfang He, Zhiqiang Li, Qing Liu
Scripta Materialia 2014 Volumes 78–79() pp:1-4
Publication Date(Web):May 2014
DOI:10.1016/j.scriptamat.2013.12.019
Microstructure of in situ Al2O3/Al composites fabricated by flake powder metallurgy (FPM) has been characterized in the current paper. The coarsening behavior of the ball-milled Al flake powders is influenced greatly by the thickness of the flakes, which in turn affects the shape and distribution of the Al2O3 reinforcement particles within the Al2O3/Al composites. Intragranular Al2O3 nanoparticles with a lamellar shape in the Al matrix could be obtained by the FPM method through refining the thickness of the ball-milled Al flakes.
Co-reporter:R.S. Qiu, B.F. Luan, L.J. Chai, X.Y. Zhang, Q. Liu
Journal of Nuclear Materials 2014 Volume 453(1–3) pp:269-274
Publication Date(Web):October 2014
DOI:10.1016/j.jnucmat.2014.07.017
In this investigation, differential scanning calorimetry (DSC) and metallographic experiments supplemented by back-scattered electron imaging (BSEI) and electron back-scattered diffraction (EBSD) techniques were performed to study the effects of heating rates and alloying elements on the α → α + β phase transformation of Zr–Sn–Nb–Fe–(Cu, Cr) alloys. Results show that the α → α + β phase transformation peaks shift to higher temperature with increasing heating rates, indicating that the reactions are thermally activated and kinetically controlled processes. The α → α + β phase transformation temperature (Tα→α+β) are affected by the solid solubility limit as well as the diffusivities of various elements in these alloys. For the zirconium alloys with low Nb contents, the Tα→α+β increases with an increase of Sn content. The addition of Cu in zirconium alloys decrease the Tα→α+β, while the addition of Cr increase it.
Co-reporter:Ning Guo;Bo Song;BaiFeng Luan;ZhiQian Chen
Science China Technological Sciences 2014 Volume 57( Issue 4) pp:796-803
Publication Date(Web):2014 April
DOI:10.1007/s11431-013-5434-8
The deformation of fully pearlitic steels during wire drawing has been investigated for both longitudinal section and transverse section by back-scattered electron imaging (BSEI), electron back-scattered diffraction (EBSD), and transmission electron microscope (TEM). The results show that a large number of deformation bands (DBs) composed of a mixture of kink-like bands and shear-like bands were observed both in the longitudinal section and the traverse section of the drawn wires. The formation of such bands involves two aspects: heterogeneous deformation in the scale of pearlite colonies and instability of ferrite-cementite interfaces due to stress concentration during wire drawing. The development of such bands in fully pearlitic steels dominates the formation of metallographic texture, reduces the pearlite interlamellar spacing and promotes the development of <110> fiber crystalline texture of ferrite matrix during wire drawing.
Co-reporter:Dr. Huijuan Zhang;Yangyang Feng;Yan Zhang;Ling Fang;Wenxiang Li; Qing Liu; Kai Wu; Yu Wang
ChemSusChem 2014 Volume 7( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/cssc.201400104
Co-reporter:Huihui Yu, Yunchang Xin, Hua Zhou, Rui Hong, Lingyu Zhao, Qing Liu
Materials Science and Engineering: A 2014 617() pp: 24-30
Publication Date(Web):
DOI:10.1016/j.msea.2014.08.034
Co-reporter:Shaohua Wu, Xiaozhi Wu, Rui Wang, Qing Liu, Liyong Gan
Intermetallics 2014 Volume 55() pp:108-117
Publication Date(Web):December 2014
DOI:10.1016/j.intermet.2014.04.022
•We investigate the effects of point defects on the SOECs and TOECs of NiAl.•Ni antisite, Cr, Pt and pressure can improve the ductility of NiAl.•Ni vacancy and lower pressure can enhance the hardness of NiAl.•The DOS and charger density difference of NiAl-based alloys are presented.Effects of Ni vacancy, Ni antisite in Al sublattice, Cr in Al sublattice, Pt in Ni sublattice on the second-order elastic constants (SOECs) and third-order elastic constants (TOECs) of the B2 NiAl have been investigated using the first-principles methods. Lattice constant and the SOECs of NiAl are in good agreement with the previous results. The brittle/ductile transition map based on Pugh ratio G/B and Cauchy pressure Pc shows that Ni antisite, Cr, Pt and pressure can improve the ductility of NiAl, respectively. Ni vacancy and lower pressure can enhance the Vickers hardness Hv of NiAl. The density of states (DOS) and the charge density difference are also used to analysis the effects of vacancy, Ni antisite, Cr and Pt on the mechanical properties of NiAl, and the results are in consistent with the transition map.
Co-reporter:Xiaozhi Wu, Lili Liu, Weiguo Li, Rui Wang, Qing Liu
Computational Condensed Matter 2014 Volume 1() pp:38-44
Publication Date(Web):December 2014
DOI:10.1016/j.cocom.2014.10.005
Temperature effect on the elastic constants and anisotropy of MgO and CaO are performed via first-principles approach combing the quasistatic approximation to elasticity and the quasiharmonic phonon approximation to thermal expansion. Generalized stacking fault energy curves at different temperature are also computed due to the importance for dislocation properties. The core structures of 1/2〈110〉{110} dislocations in MgO and CaO at different temperature are investigated within the improved Peierls–Nabarro dislocation theory using Foreman's method. It is found that the core width of dislocation increases with the increasing of temperature.
Co-reporter:Dr. Huijuan Zhang;Yangyang Feng;Yan Zhang;Ling Fang;Wenxiang Li; Qing Liu; Kai Wu; Yu Wang
ChemSusChem 2014 Volume 7( Issue 7) pp:2000-2006
Publication Date(Web):
DOI:10.1002/cssc.201301394
Abstract
Herein, we introduce a peapod-like composite with Ni12P5 nanoparticles encapsulated in carbon fibers as the enhanced anode in Li-ion batteries for the first time. In the synthesis, NiNH4PO4⋅H2O nanorods act as precursors and sacrificial templates, and glucose molecules serve as the green carbon source. With the aid of hydrogen bonding between the precursor and carbon source, a polymer layer is hydrothermally formed and then rationally converted into carbon fibers upon inert calcination at elevated temperatures. Meanwhile, NiNH4PO4⋅H2O nanorods simultaneously turn into Ni12P5 nanoparticles encapsulated in carbon fibers by undergoing a decomposition and reduction process induced by high temperature and the carbon fibers. The obtained composite performs excellently as a Li-ion batteries anode relative to pure-phase materials. Specific capacity can reach 600 mAh g−1 over 200 cycles, which is much higher than that of isolated graphitized carbon or phosphides, and reasonably believed to originate from the synergistic effect based on the combination of Ni12P5 nanoparticles and carbon fibers. Due to the benignity, sustainability, low cost, and abundance of raw materials of the peapod-like composite, numerous potential applications, in fields such as optoelectronics, electronics, specific catalysis, gas sensing, and biotechnology can be envisaged.
Co-reporter:Linjiang Chai, Baifeng Luan, Korukonda L. Murty, Qing Liu
Acta Materialia 2013 Volume 61(Issue 8) pp:3099-3109
Publication Date(Web):May 2013
DOI:10.1016/j.actamat.2013.02.001
Abstract
In this paper, we report the effect of a 20% predeformation on the microstructural evolution of a Zr–0.85Sn–0.4Nb–0.4Fe–0.1Cr–0.05Cu alloy during aging between 550 and 700 °C after β quenching. Transmission electron microscopy, electron backscatter diffraction, electron channeling contrast and secondary electron imaging techniques are jointly utilized to carry out detailed microstructural characterization. By comparing microstructures between directly aged specimens (group A) and specimens aged after a 20% predeformation (group B), it is revealed that the introduced predeformation could exert remarkable influences on the Zr alloy. As the aging temperature and/or time increase, initial plate structures finally recrystallize in both groups. In spite of the similarity of the general evolution profile, the predeformation introduced in group B evidently reduces the required aging temperature and time. Distinct recrystallization nucleation behaviors due to different recrystallization mechanisms are also found in both groups. Noticeable differences between the with- and without-predeformation groups also include grain size, distribution of second-phase particles and misorientation angle distribution features in recrystallized specimens. Reasons accounting for the accelerated recrystallization and distinct microstructural characteristics in group B are discussed and attributed to the defects introduced during the predeformation. In addition, grain size calculation by applying the Zener equation shows that, although equilibrium states are not attained in both groups, the case with the predeformation is closer to the ideal equilibrium.
Co-reporter:Liping Deng, Xiaofang Yang, Ke Han, Yafeng Lu, Ming Liang, Qing Liu
Materials Characterization 2013 Volume 81() pp:124-133
Publication Date(Web):July 2013
DOI:10.1016/j.matchar.2013.04.013
Co-reporter:Nali Li, Guangjie Huang, Renlong Xin, Qing Liu
Materials Science and Engineering: A 2013 Volume 569() pp:18-26
Publication Date(Web):1 May 2013
DOI:10.1016/j.msea.2013.01.027
AZ31 magnesium alloy with two different forms of initial textures were extruded at 573 K to investigate the effect of initial texture on dynamic recrystallization (DRX) and deformation mechanisms. It reveals that the initial texture significantly affected twinning behavior. Hardly any twins were found in the extruded and annealed (EA) rod while {10−12} extension twins were observed to be very active in the rolled and annealed (RA) rod. DRX in the RA rod was retarded compared with that in the EA rod. The delay of DRX in the RA rods was attributed to the different deformation mechanisms occurring before DRX initiation. For the EA rod, dislocation slip was considered as the main deformation mechanism at the initial stage of extrusion which resulted in a faster increasing of the stored energy within the grains and consequently DRX was initiated. For the RA rod, {10−12} extension twin was a dominant deformation mechanism at the initial stage of extrusion before DRX initiated which resulted in an extrusion texture with the basal planes parallel to the extrusion direction (ED). Because of the profuse twinning, the stored energy caused by dislocation motion was relatively small in the RA rod, which was considered as the main reason of the delay of DRX in the RA rod. However, although the initial texture had great influence on DRX and deformation mechanisms during extrusion it had no significant effect on final fully DRX extrusion microstructure. DRX is a texture weakening process during extrusion. A weak fiber texture with the basal planes parallel to ED but without any specific crystallographic direction parallel to ED was obtained in the fully DRX extrusion microstructure.
Co-reporter:Linjiang Chai, Baifeng Luan, Min Zhang, Korukonda L. Murty, Qing Liu
Journal of Nuclear Materials 2013 440(1–3) pp: 377-381
Publication Date(Web):
DOI:10.1016/j.jnucmat.2013.05.053
Co-reporter:Ning Guo;BaiFeng Luan;BingShu Wang
Science China Technological Sciences 2013 Volume 56( Issue 5) pp:1139-1146
Publication Date(Web):2013 May
DOI:10.1007/s11431-013-5184-7
The evolution of morphology of pearlite and crystallographic texture of ferrite matrix in fully pearlitic steels during wire drawing were quantitatively investigated. The study revealed that a fiber structure of the pearlite morphology and a <110> fiber texture of the ferrite matrix begin to take shape and develop gradually with increasing strain. The growth rates of the fiber structure and the <110> texture are different in different regions within the wires with increasing drawing strain. There is a close relationship between the pearlite morphology and the crystalline texture during wire drawing. The pearlite interlamellar spacing (ILS) and thickness of cementite lamellae (Tθ) decrease gradually both in longitudinal and transverse sections. The definition of pearlite colony should be reconsidered for describing microstructure of the wire drawing deformed pearlitic steels.
Co-reporter:Ning Guo, Baifeng Luan, Qing Liu
Materials & Design 2013 50() pp: 285-292
Publication Date(Web):
DOI:10.1016/j.matdes.2013.02.047
Co-reporter:Nali Li, Guangjie Huang, Xiaoyu Zhong, Qing Liu
Materials & Design 2013 50() pp: 382-391
Publication Date(Web):
DOI:10.1016/j.matdes.2013.03.028
Co-reporter:J.R. Luo, A. Godfrey, W. Liu, Q. Liu
Acta Materialia 2012 Volume 60(Issue 5) pp:1986-1998
Publication Date(Web):March 2012
DOI:10.1016/j.actamat.2011.12.017
Abstract
The twinning behavior of a strongly basal textured magnesium alloy AZ31 plate during warm rolling to a reduction of 9% has been investigated. Analysis of the twin types and twin variants was carried out based on orientation data collected using electron backscatter diffraction. Double twins (corresponding to contraction twinning followed by extension twinning) were the most commonly observed twin type, with more than 70% of the grains examined containing this type of twin. The double twin variant with a 38° misorientation to the original grain orientation was the most frequently observed, with the 30° variant being the next most frequently observed. The twinning variant selection was analyzed using both a modified Schmid factor for rolling and by use of normal strain maps, used to show the compatibility between the normal strains due to twinning and the applied rolling deformation. It was found that the 38° and 30° misorientation double twin variants provide normal strains that are similarly compatible with the applied deformation, with a slight advantage for the 30° variant. Overall, the results show that for rolling deformation external strain accommodation, rather than self-strain accommodation, is the dominant factor in determining the variant types of the double twins formed during warm rolling.
Co-reporter:Renlong Xin, Yuanming Luo, Ailing Zuo, Jiacheng Gao, Qing Liu
Materials Letters 2012 Volume 72() pp:1-4
Publication Date(Web):1 April 2012
DOI:10.1016/j.matlet.2011.11.032
The texture effect of AZ31 Mg alloy on its corrosion resistance in simulated body fluid (SBF) at 37 °C was examined by hydrogen evolution method, polarization curve and electrochemical impedance spectrum. It was found that at the early immersion time, the sample with c-axis of most grains normal to the exposed surface exhibited much higher corrosion resistance than the sample consisting mainly of (101¯0) and (112¯0) oriented grains. But after about 46 h of immersion, the corrosion rate of both samples was largely reduced, less than 0.011 ml/cm2/h due to the deposition of a film on surfaces. The profound texture effect on the corrosion resistance in SBF opened a new window to control the corrosion property of Mg alloys for biomedical applications.
Co-reporter:Feng Xu, Xiyan Zhang, Haitao Ni, Qing Liu
Materials Science and Engineering: A 2012 Volume 541() pp:190-195
Publication Date(Web):15 April 2012
DOI:10.1016/j.msea.2012.02.021
The type of deformation twins in purity titanium after dynamic plastic deformation (DPD) and quasi-static compression (QSC) at room temperature is investigated by electron backscatter diffraction techniques, respectively. DPD with a high strain rate (4.5–5 × 102/s) activates more deformation twins in Ti. Four types of twins have been identified in DPD samples, while three types of twins in QSC samples. The {1 1 2¯ 4} twinning is only observed in DPD samples, associating with the {1 1 2¯ 2} twinning. The misorientations of {1 1 2¯ 2}–{1 1 2¯ 4} variant pairs are 12–13°, suggesting they follow the same misorientation profile (0 1 1¯ 0) plane and rotated direction.Highlights► Pure Ti samples were deformed by dynamic plastic deformation (DPD). ► There were four and tree types of deformation twins during DPD and quasi-static compression, respectively. ► {1 1 2¯ 4} twinning was only found in DPD samples. ► The high strain rate affected the formation of {1 1 2¯ 4} twinning
Co-reporter:Bingshu Wang, Renlong Xin, Guangjie Huang, Qing Liu
Materials Science and Engineering: A 2012 Volume 534() pp:588-593
Publication Date(Web):1 February 2012
DOI:10.1016/j.msea.2011.12.013
Co-reporter:D.L. Zou, B.F. Luan, Q. Liu, L.J. Chai, J.W. Chen
Materials Science and Engineering: A 2012 Volume 558() pp:517-524
Publication Date(Web):15 December 2012
DOI:10.1016/j.msea.2012.08.038
The adiabatic shear bands formed in the zirconium alloy impacted by split Hopkinson pressure bar at a strain rate of about 6000 s−1 were characterized systemically by means of a high resolution field emission scanning electron microscope equipped with electron backscatter diffraction probe. The results show that the transformed bands were distinguished on the cross-section view of the impacted specimens, and the ultrafine and equiaxed grains formed in the transformed bands were confirmed. The gradient variation of the grains across the transformed bands from the boundary to the center of the bands was observed, and the grains at the center of the transformed bands were finer than other zones. Based on the characterization of the deformed microstructure adjacent to the transformed bands, the formation mechanism of the ultrafine and equiaxed grains in the transformed bands was revealed, and the rotational dynamic recrystallization mechanism should be responsible for the formation of the ultrafine and equiaxed grains in the transformed bands. According to the collection of the cumulative misorientation at different strain levels, the formation and evolution process of the ultrafine and equiaxed grains in the transformed bands were speculated. The microhardness measurements show that high microhardness value in the transformed bands was obtained because of the grain refining, and the large standard deviation of the microhardness at the center of the transformed bands was confirmed due to the gradient microstructural distribution in the bands.
Co-reporter:NaLi Li;GuangJie Huang;RenLong Xin
Science China Technological Sciences 2012 Volume 55( Issue 2) pp:490-495
Publication Date(Web):2012 February
DOI:10.1007/s11431-011-4671-y
Experiments were conducted to evaluate the effects of extrusion ratio on the microstructure and texture developments of AZ31 Mg alloy during forward extrusion. The forward extrusion was undertaken at 400°C with extrusion ratios of 10, 18, and 25 after the alloy was homogenized at 410°C for 12 h. Partially recrystallized microstructures were observed in all the extruded rods examined. The texture of the large elongated deformed grains appeared strongly centered at \(\left\langle {10\bar 10} \right\rangle\) dominating the extrusion texture, while the recrystallized grains exhibited much more randomized texture. For the alloy with the largest ER (25), coarse secondary recrystallized grains were found which presented a different texture component with \(\left\langle {11\bar 20} \right\rangle\) parallel to the ED. The occurrence of the coarse secondary recrystallized grains in the alloy with the largest ER might be attributed to that the large ER raised the die exit temperature during extrusion and thus promoted significantly grain growth after the extruded rod exited from extrusion die. The intensities of different texture components varied with ER because ER affected the contents of the deformed grains, DRX grains and coarse secondary recrystallized grains. In particular, the maximum intensity of fiber texture was decreased as ER increased due to the decrease of the large elongated deformed grains.
Co-reporter:Ning Guo;YunChang Xin;BaiFeng Luan
Science China Technological Sciences 2011 Volume 54( Issue 9) pp:
Publication Date(Web):2011 September
DOI:10.1007/s11431-011-4500-3
The microstructures of pearlitic steel wire rods and steel wires are commonly characterized by secondary electron imaging (SEI) technique using scanning electron microscopy (SEM). In this work, a back-scattered electron imaging (BSEI) method is proposed to determine the microstructures of undeformed and deformed pearlitic steels with nanometer scale pearlite lamellae. The results indicate that BSEI technique can characterize the pearlite lamellas veritably and is effective in quantitative measurement of the mean size of pearlite interlamellar spacing. To some extent, BSEI method is more suitable than SEI technique for studying undeformed and not severely deformed pearlitic steels.
Co-reporter:Maoyin Wang, Renlong Xin, Bingshu Wang, Qing Liu
Materials Science and Engineering: A 2011 528(6) pp: 2941-2951
Publication Date(Web):
DOI:10.1016/j.msea.2010.11.069
Co-reporter:Y.T. Zhu, X.Y. Zhang, Q. Liu
Materials Science and Engineering: A 2011 528(28) pp: 8145-8149
Publication Date(Web):
DOI:10.1016/j.msea.2011.07.062
Co-reporter:Qing Liu, Zongyong Yao, Andrew Godfrey, Wei Liu
Journal of Alloys and Compounds 2009 Volume 482(1–2) pp:264-271
Publication Date(Web):12 August 2009
DOI:10.1016/j.jallcom.2009.03.183
The effect of second-phase particles on the evolution of the deformation microstructure during cold rolling of the particle-containing aluminum alloy AA3104 has been investigated using electron channeling contrast imaging and electron backscattered diffraction (EBSD). The results show that the influence of second-phase particles on the deformation microstructure depends on the particle size. Fine dispersoids present in the microstructure have no clear effect on the grain orientation dependence of the dislocation structures formed in the strain range examined. However, large scale structural heterogeneities, in the form of deformation zones, are formed near coarse constituent particles, leading to significant local distortions of the deformed microstructure. Analysis of EBSD data shows that significant orientation gradients are found in the vicinity of the coarse particles. Within the deformation zones the largest lattice rotations occur at the tips of plate-shaped constituent particles. A symmetrical pattern of TD-rotations of alternating sign is found in the deformation zones, with the magnitude of the lattice rotations increasing with increasing strain.
Co-reporter:Jia Jiang;Andy Godfreyb
Science China Technological Sciences 2009 Volume 52( Issue 1) pp:
Publication Date(Web):2009 January
DOI:10.1007/s11431-008-0292-5
The evolution of the microstructure and texture with strain during compression at 150° of the magnesium alloy AZ31 has been investigated using the electron backscattered diffraction (EBSD) technique. The initial samples were chosen to have a strong basal plane texture with the crystal c-axes perpendicular to the compression direction. The EBSD data provide evidence concerning the relative activity of both {10–12} extension twinning and slip, and suggest that non-basal slip is important in samples deformed to a strain of more than 0.2. The relative contributions of the twinning and the slip during deformation have been discussed based on the results above.
Co-reporter:Yun Zou, Qing Liu, Zhihong Jia, Yuan Xing, Lipeng Ding, Xueli Wang
Applied Surface Science (31 May 2017) Volume 405() pp:
Publication Date(Web):31 May 2017
DOI:10.1016/j.apsusc.2017.02.045
•High Cu alloy with high Mg/Si ratio has the best comprehensive property.•Addition of excess Mg could improve the intergranular corrosion resistance.•Si containing particles on the grain boundaries of Si-rich alloys promote IGC.•IGC susceptibility depends primarily on Cu content and secondarily on Mg/Si ratio.6000-series aluminium alloys with high Cu or excess Si addition were susceptible to intergranular corrosion (IGC). In order to obtain good IGC resistance, four alloys with low/high Cu and various Mg/Si ratios were designed. The corrosion behaviour of four alloys was investigated by accelerated corrosion test, electrochemical test and electron microscopies. It was revealed that IGC susceptibility of alloys was the result of microgalvanic coupling between the noble grain boundary precipitates and the adjacent precipitates free zone (PFZ), which was closely related to a combination of Cu content and the Mg/Si ratio. Excess Mg could improve the IGC resistance of alloys by forming discontinuous precipitates on the grain boundaries. The designed alloy with high Cu and excess Mg has the same corrosion level as the commercial alloy with low Cu and excess Si, which provides possibility for developing new alloy.
Co-reporter:Huihui Yu, Changzheng Li, Yunchang Xin, Adrien Chapuis, Xiaoxu Huang, Qing Liu
Acta Materialia (15 April 2017) Volume 128() pp:
Publication Date(Web):15 April 2017
DOI:10.1016/j.actamat.2017.02.044
A Hall-Petch slope (k) that is highly changeable with texture, as extensively reported in Mg alloys, is ultimately related to the variation of deformation modes. In this paper, the influence of different (0002) distributions on k for twinning and slip was systematically studied using an AZ31 rolled plate ([0002]//ND) and extruded rod ([0002]⊥ED together with a random distribution around the ED). The ND and ED refer to the normal direction of the plate and extrusion direction of the rod, respectively. A high dependency of k on the (0002) distribution is found, namely, a much lower k for {101¯2} twinning in the plate (219 MPa μm1/2) than that in the rod (435 MPa μm1/2), but a much higher k for slip in the plate (437 MPa μm1/2) than that in the rod (235 MPa μm1/2). Compound use of the difference in Schmid factor (ΔSF ) and geometric compatibility factor (m′m′) quantitatively explains this orientation effect on k. ΔSF relates to the extra stress needed for the activation of slip/twinning in a neighboring grain, and m′m′ reflects the efficiency of the stress concentration at the onset of slip/twinning in an adjacent grain. The lower m′m′ for twinning in the rod versus the plate primarily accounts for the higher k for twinning in the rod. A much larger inclination of basal poles away from the ideal texture exists in the plate than in the rod, which induces a higher activity of basal slip during tension. The resultant high fraction of slip transfer from basal slip in one grain to prismatic slip in the neighboring grain largely amplifies ΔSF and reduces m′m′, both of which yield a higher k for slip in the plate than in the rod. The relationship between the crystallographic orientation and m′m′ was also calculated for different types of deformation transfer, and the main factor that determines m′m′ was revealed.
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