Co-reporter:Guoju Li, Ran Shi, Qunbo Fan, Yumeng Xia, Hongmei Zhang
Materials Science and Engineering: A 2017 Volume 685(Volume 685) pp:
Publication Date(Web):8 February 2017
DOI:10.1016/j.msea.2017.01.025
A new in-depth evaluation of the micromechanical response of TC6 (Ti–6Al–1.5Cr–2.5Mo–0.5Fe–0.3Si) titanium alloy subjected to uniaxial tensile loading is performed based on micromechanical modeling. This evaluation includes reconstruction of the three-dimensional annealed microstructure (annealing at 800 °C for 2 h, then air cooled) of the alloy via dual-energy micro-computed tomography. In addition, constitutive relations of the constituent phases were determined via synchrotron-based in-situ high-energy X-ray diffraction and a self-consistent model as well as nanoindentation tests combined with finite element modeling. The results revealed that the stress concentration was translated from the primary α phase to the secondary α phase, then to the β phase. Moreover, the stress generated was re-transferred to the primary α phase when the strain was increased from 0.00 to 0.05. This transfer is indicative of crack initiation in the primary α grains.
Co-reporter:Guoju Li, Ran Shi, Qunbo Fan, Yumeng Xia, Hongmei Zhang
Materials Science and Engineering: A 2016 Volume 675() pp:212-220
Publication Date(Web):15 October 2016
DOI:10.1016/j.msea.2016.08.078
In the present study, dual-energy micro-computed tomography (Micro-CT) imaging was employed to overcome the difficulty of low absorption contrast due to the low difference in density among the primary α phase, secondary α phase, and β phase of the annealed microstructure (annealing at 800 °C for 2 h followed by air cooling) of TC6 titanium alloy. The three dimensional microstructure model of TC6 titanium alloy was first achieved by laboratory X-ray microtomography, and then analyzed quantitatively. It is found that the volume fractions of the primary α phase, secondary α phase and β phase are 28.32%, 47.78% and 23.90%, respectively. Some complex microstructural features of TC6 titanium alloy such as spatial distribution, shapes, and interconnectivities that can hardly be described by the conventional two dimensional microscopy technique were successfully captured. In three dimensional space, the primary α phase is composed of discrete equiaxed grains and interconnected grains, and the fraction of the individual equiaxed grains is up to 50% and the average diameter is about 10 µm; the secondary α phase interconnects with β phase forming a completely interconnected network.
Co-reporter:Ran Shi, Guoju Li, Zhihua Nie, Qunbo Fan
Materials Science and Engineering: A 2016 Volume 675() pp:138-146
Publication Date(Web):15 October 2016
DOI:10.1016/j.msea.2016.08.057
The constitutive relations of α and β phases in a TC6 titanium alloy were determined by implementing a two-phase elastic-plastic self-consistent (EPSC) framework combined with the evolution of lattice strains; these strains were obtained via in-situ tensile loading synchrotron-based x-ray diffraction experiments. It was found that the {200}β reflection has the lowest stiffness and load partitions prior to the α phase during the elastic loading stage in this alloy. The simulated parameters including the diffraction elastic constant and initial yield stress of lattice reflections exhibited satisfactory correspondence with the experimental results. Further analysis of the characteristics of the Schmid Factor (SF) distributions of the main slip systems revealed that the elastic-plastic transition process in the α phase occurs over a prolonged period. In contrast, the β phase undergoes a transient process owing to its relatively more concentrated SF frequency distributions, than those of the α phase. In addition, the fitted stress-strain curve of each phase was compared with the measured macro stress-strain curve obtained from the in-situ experiment. It revealed Young's moduli of 110.3 GPa and 104.5 GPa, and yield stresses of 877.8 MPa and 969 MPa, for the α and β phases, respectively.
Co-reporter:Guoju Li, Xu Zhang, Qunbo Fan, Linlin Wang, Hongmei Zhang, Fuchi Wang, Yangwei Wang
Acta Materialia 2014 Volume 78() pp:190-202
Publication Date(Web):1 October 2014
DOI:10.1016/j.actamat.2014.06.045
Abstract
In the current study, a 3-D microscopic structural finite element (FE) model of interpenetrating SiC/Al composites (SiC/Al IPCs) is built, based on X-ray tomography and optimized methods for 3-D mesh generation. In addition, an interface model is introduced into the 3-D FE model to investigate the effects of the interfaces on the damage and failure processes, which includes a “tie-break contact” method at the SiC/Al interfaces. Subsequently, FE methods are applied to investigate the dynamic compression response of the 3-D FE model. To validate the numerical simulation results, the dynamic compression responses of SiC/Al IPCs are measured at strain rates of 2000 s−1 using a split Hopkinson pressure bar device. Our results show that failure of the SiC phase occurs just before the effective stress reaches its peak, but it plays a leading role in bearing the pre-metaphase stage of the load. From the point of energy dissipation, however, the contribution of Al phase cannot be ignored in the final stage of failure because the residual Al phase absorbs 30% of the energy of the global model by plastic deformation, even though its mass failure ratio is only 2%. Further microanalysis shows that the cracks initiate and propagate mainly near the SiC/Al interface, just on the side of the SiC ceramic phase. As the cracks extend further into the SiC phase, there appears a new “interface debonding” failure mode. These results show that brittle fracture of the SiC ceramic phase plays a key role in crack initiation, since the presence of complex 3-D SiC/Al interfaces usually causes the generated cracks to deflect before interconnecting with each other. This significantly retards propagation of the cracks, and thus increases the ductility of the composite materials. In the final stage of failure, the cracks are interconnected with each other in the SiC phase while the Al phase still maintains a degree of structural integrity. It is found that there exists obvious plastic deformation in local, relatively narrow, regions in the Al phase, and the local necking and tearing fractures tend to be localized in these severely deformed regions. Numerical simulation results are consistent with the observed behavior.
Co-reporter:Rongting Li, Qunbo Fan, Ruihua Gao, Lirui Huo, Fuchi Wang, Yangwei Wang
Materials & Design 2014 62() pp: 233-240
Publication Date(Web):
DOI:10.1016/j.matdes.2014.05.044
Co-reporter:Shen Wei, Wang Fu-chi, Fan Qun-bo, Ma Zhuang
Surface and Coatings Technology 2013 Volume 217() pp:39-45
Publication Date(Web):25 February 2013
DOI:10.1016/j.surfcoat.2012.11.069
Relying on the statistical treatment of the morphological characteristics of the interface between yttria stabilized zicronia (YSZ) top coat (TC) and metallic bond coat (BC), finite element model of thermal barrier coating (TBC) is generated by a sinusoidal function. Meanwhile, considering the thermally grown oxide (TGO) growth, creep effects and top coating sintering, lifetime prediction methodology is proposed. Furthermore, stress development during thermal cycling is calculated by finite element method (FEM). Comparing the numerically predicted TBC stresses with the failure stress of top coating, the lifetime of plasma-sprayed (PS) TBC is predicted between 810 and 900 cycles, in agreement with experimental result of about 860 cycles, the average data of 8 specimen lifetimes. Different factors to the failure of TBC are compared.Highlights► Considering TGO, creep and sintering, lifetime prediction methodology is proposed. ► Stress development during thermal cycling is calculated by FEM. ► The predicted lifetime of PS TBC is in agreement with experimental result.
Co-reporter:Dongmei Huo, Shukui Li, Qunbo Fan, Fuchi Wang
Materials Science and Engineering: A 2011 530() pp: 161-167
Publication Date(Web):
DOI:10.1016/j.msea.2011.09.067
Co-reporter:Shen Wei, Wang Fu-chi, Fan Qun-bo, Ma Zhuang, Yang Xue-wen
Surface and Coatings Technology 2011 205(8–9) pp: 2964-2969
Publication Date(Web):
DOI:10.1016/j.surfcoat.2010.11.003
Co-reporter:Shen Wei, Wang Fu-chi, Fan Qun-bo, Hua Dan, Ma Zhuang
Surface and Coatings Technology 2010 204(21–22) pp: 3376-3381
Publication Date(Web):
DOI:10.1016/j.surfcoat.2010.03.057
Co-reporter:Fan Qunbo, Wang Lu, Wang Fuchi
Journal of Materials Processing Technology 2008 Volume 198(1–3) pp:207-212
Publication Date(Web):3 March 2008
DOI:10.1016/j.jmatprotec.2007.07.008
In plasma spray, operation parameters, including current, flow rate of primary gas, and flow rate of secondary gas, would influence the heat and acceleration status of particles greatly, thus influencing the coating's final quality. As the first stage to optimize the spraying technology, this paper investigates the typical Ar–He plasma spray process, analyzing the influence mechanism of current, flow rate of Ar, as well as flow rate of He on the temperature field and velocity field. The chemical reactions and turbulence are fully taken into account. It is found that the electrical current is apparently influential to both the jet temperature and velocity, and further the ionization of Ar atoms. With increasing Ar or He flow rates independently, the temperature of the plasma jet will be decreased, and the velocity of the plasma jet will be increased. Related inner mechanisms are revealed in detail. The results presented in this paper would be theoretically helpful for further study of the interaction between the plasma jet and the particles, and the optimization of the plasma-spraying technology.
Co-reporter:Fan Qunbo;Wang Fuchi;Wang Lu
Journal of Materials Engineering and Performance 2008 Volume 17( Issue 5) pp:621-626
Publication Date(Web):2008 October
DOI:10.1007/s11665-007-9187-z
In this article, the trajectories of ceramic and metal particles in plasma spray are calculated by solving related momentum and energy equations. Meanwhile, the spatial distributions, temperatures, velocities, as well as diameters of the particles are measured by employing an online, in-flight particle sensor (DPV2000). The experimental and computational results are in good agreement. It has been found that the particle flying trajectories are dependent on material types and particle diameters, and in a plane vertical to the spraying axis, there is a certain corresponding relationship between the particle diameter and the particle velocity, as well as particle temperature.
Co-reporter:Ran Shi, Guoju Li, Yumeng Xia, Qunbo Fan, Fuchi Wang, Hongmei Zhang, Xingwang Cheng
Journal of Alloys and Compounds (25 May 2017) Volume 705() pp:
Publication Date(Web):25 May 2017
DOI:10.1016/j.jallcom.2017.02.132
•Microstructural evolutions of α and β phases during recrystallization were tracked.•The β phase was found to have a higher recrystallization rate and fraction.•Spatial grain morphologies and orientations were revealed by 3D FIB–EBSD.•Globular and equiaxed α grains were found well dispersed in sub-structured β matrix.An α+β type titanium alloy was subjected to various periods of recrystallization annealing and the resulting microstructural evolution was characterized. The results revealed that the recrystallization rate of the β phase was higher than that of the α phase, owing to the high strain energy storage of this phase during large deformation forging. Moreover, the recrystallized fraction of both the α and β phases increased with increasing holding time at 740 °C. The recrystallization fraction of the β phase accounted for 70.13% after annealing for 5 h. However, the average grain size remained constant when the recrystallization fraction reached approximately 54%, indicating that further grain refinement was prevented, owing to the high degree of recrystallization. The spatial microstructure which consisted of a globular, homogeneous, and equiaxed α phase dispersed in sub-structured β matrix grains, was characterized via a novel three-dimensional electron backscatter diffraction technique. The grain orientation and morphological parameters, including the equivalent-sphere diameter and number of neighboring grains, were calculated and discussed.
