As metallic foams used for energy absorption in the automotive and aerospace industries, recently invented lotus-type porous metals are viewed as potential energy absorbers. Yet, solid conclusion on their eligibility as energy absorbers is still in question, particularly when compression is in the direction perpendicular to the axial orientation of cylindrical pores. In this work, the energy absorption of lotus-type porous coppers in the perpendicular direction is investigated at strain rates from 0.001 s−1 to ∼2400 s−1. The energy absorption capacity and the energy absorption efficiency are calculated to be 4–16 kJ/kg and 0.32–0.7, respectively, slightly inferior to metal foams and the same porous solid compressed in the parallel direction due to the shortened extent of the plateau stress region. The deformation mechanism is examined experimentally in conjunction with finite element modeling. Both suggest that gradual squeeze and collapse of pores are the mechanisms accommodating the energy absorption. The deformation is generally evenly distributed over pore ligaments and independent of strain rate.

The influences of rolling reduction and aluminum sheet initial thickness (AIT) on the thickness fluctuation of aluminum layer (TFA) of embedded aluminum–steel composite sheet produced by cold roll bonding were investigated, the formation mechanism of TFA was analyzed and method to improve the thickness uniformity of the aluminum layer was proposed. The results showed that when the reduction increased, TFA increased gradually. When the reduction was lower than 40%, AIT had negligible effect on the TFA, while TFA increased with the decrease of AIT when the reduction was higher than 40%. The non-uniformities of the steel surface deformation and the interfacial bonding extent caused by the work-hardened steel surface layer, were the main reasons for the formation of TFA. Adopting an appropriate surface treatment can help to decrease the hardening extent of the steel surface for improving the deformation uniformity during cold roll bonding process, which effectively improved the aluminum thickness uniformity of the embedded aluminum/steel composite sheets.

The effects of rolling deformation, rolling temperature and aging treatment on microstructure and mechanical properties of Cu-Cr-Zr alloy were investigated and the relevant influencing mechanism was also discussed in this study. The results showed that the tensile strength of the Cu-Cr-Zr alloy increased with an increase of rolling deformation at room temperature. The elongation to failure of the alloy decreased until the rolling reduction is up to 80% and then increased with the reduction, which is related to the grain orientation change from Copper texture with poor plasticity to the Goss/Brass texture with good plasticity. A large amount of Cr precipitates were identified during rolling at 300 °C in Cu-Cr-Zr alloy, which resulted in much higher electrical conductivity and tensile strength exceeded that of the room-temperature rolling with the rolling reduction over 80%. Aging treatment of 450 °C for 1 h led to the formation of massive Cr and Cu4Zr precipitates, which can significantly improve the tensile strength from 591.1 MPa to 669.1 MPa and electrical conductivity from 30.3%IACS to 74.5%IACS of the room-temperature rolled alloy. These results provide a guideline for exploring efficient preparation methods of high-performance Cu-Cr-Zr alloys.

•Superelasticity of Cu-Al-Ni alloy has ultra-low dependence on loading frequency.•The alloy can sustain over 2000 tensile cycles at the applied total strain of 4%.•The alloy exhibits excellent cyclic stress-strain response and fatigue life.•The alloy is a promising substitution for Ni-Ti alloy in seismic protection field.Our previous study developed a polycrystalline Cu-Al-Ni alloy by directional solidification, which exhibits excellent superelasticity. To further verify the application feasibility of the Cu-Al-Ni alloy, cyclic superelastic behaviors of the alloy under varying loading frequencies and strain amplitudes were investigated in this study. The results show that the superelasticity of the polycrystalline Cu-Al-Ni alloy has ultra-low dependence on loading frequency in a range of 0.005∼5 Hz. The alloy can sustain over 2000 tensile cycles at the applied total strain of 4%, exhibiting 1750 cycles and 825 cycles for total strain of 6% and 8%, respectively. The normalized critical stress and strain vary only ∼10% and ∼0.03% after 2000 times of loading-unloading with a strain amplitude of 4%. Compared with the commercial polycrystalline Ni-Ti alloy, the directionally solidified Cu-Al-Ni alloys with columnar grains exhibit excellent cyclic stress-strain response and fatigue life, which are promising materials for energy absorption and seismic protection structures or components.

•FeNiCoAlTaB alloy with good superelasticity was fabricated by a new method.•Alloy grain orientation was controlled by directional solidification technology.•Precipitates morphology and distribution were controlled by solution-aging treatment.•Parameters of directional solidification and solution-aging were firstly confirmed.FeNiCoAlTaB alloy with good superelasticity was fabricated by using the directional solidification technology to control grain orientation and solution-aging treatment to change the morphology and distribution of precipitates, and the superelasticity improving mechanism of the alloy was investigated in this study. The results indicated that with the melt zone temperature of 1420 ± 5 °C and withdrawing velocity of 0.5 mm/min, the columnar-grained FeNiCoAlTaB alloy with strong 〈100〉 fiber texture was obtained. After solution treatment at 1315 °C for 20 min and aging at 700 °C for 6 h, the columnar-grained FeNiCoAlTaB alloy exhibited the superelasticity strain of 1.7%, residual strain of 0.5% and tensile strength of 860 MPa. Compared with the non-superelastic equiaxed-grained alloy fabricated by vacuum melting and forging, the desired grain orientation, the size and distribution of the precipitates resulted in the good superelasticity of the columnar-grained FeNiCoAlTaB alloy.

•Grain orientation dependence of twinning is identified in a Fe-6.5 wt%Si alloy.•Ductility of the alloy can be improved significantly by grain orientation control.•Alloy strips can be easily manufactured by warm rolling applying the above results.The deformation behaviours of the equiaxed-grained and columnar-grained Fe-6.5 wt%Si alloy were comparatively studied and the mechanism of the enhanced deformation properties of columnar-grained alloys was discussed. A grain orientation dependence of the deformation twinning was identified in the Fe-6.5 wt%Si alloy. Twins tend to occur in grains with a tensile orientation near the <001> corner and a compressive orientation near the <101>–<111> line, which is closely related to the Schmid factor value of each orientation. The significant enhancement of the deformation properties of the columnar-grained Fe-6.5 wt%Si alloy was mainly ascribed to the promotion of twinning deformation by the grain orientation control. These results provide a theoretical guide for the microstructure design of brittle metals, such as Fe-6.5 wt%Si alloy.

•Fe–6.5 wt%Si alloy's poor ductility is mainly caused by brittle ordered structure.•Quenching and deformation treatments are mainstream methods to reduce order degree.•We found that rare earth elements doping can significantly reduce order degree.•Order–disorder transformations are hindered by doped rare earth atoms.•Order degree reduction lead to the significant tensile ductility improvement.Fe–6.5 wt%Si alloy's poor ductility is mainly caused by the large amount of brittle ordered structure, and the significant reduction of Fe–6.5 wt%Si alloy's order degree was found by rare earth elements (yttrium, lanthanum, cerium) doping, hence the average room temperature bending deflection increases to 0.77 mm from 0.62 mm and the average tensile elongation to failure at 400 °C increases to 23.0% from 7.3% by 0.021 wt% cerium doping. The order degree reduction phenomenon was manifested by the obvious decrease of B2 and D03 ordered structure reflection intensity in X-ray diffraction and selected area electron diffraction patterns and the ordered domains refinement in transmission electron microscopy. The rearrangement capability of adjacent atoms during order–disorder transformations is lowered due to the iron and silicon atoms are dragged by rare earth atoms, hence the formation of ordered phases is hindered, which provides a novel order degree reduction mechanism of Fe–6.5 wt%Si alloy.

•Effects of warm-rolling process on the Fe–6.5wt%Si alloy were studied.•The plasticity and cold-rolling workability of Fe–6.5wt%Si alloy were improved.•The microstructure, ordering and oxidation of the warm-rolled alloy were analyzed.•A technical idea of warm-rolling with gradually decreasing temperature is proposed.The effects of warm-rolling process on the microstructure, ordering, mechanical properties and cold-rolling workability of Fe–6.5wt%Si alloy were investigated, where three processes of warm-rolling with the same total reduction of 93% were used, including (1) 500 °C/12 passes/total reduction of 93%, (2) 500 °C/3 passes/total reduction of 50% + 400 °C/9 passes/total reduction of 86%, and (3) 500 °C/3 passes/total reduction of 50% + 400 °C/5 passes/total reduction of 60% + 300 °C/4 passes/total reduction of 64%. The results show that compared with process (1) warm-rolling with constant temperature of 500 °C, process (2) and process (3) warm-rolling with gradually decreasing temperature can significantly improve the room temperature plasticity and cold-rolling workability of the Fe–6.5wt%Si alloy. For example, the three point bending fracture deflections are increased by 54.5% and 81.8% for processes (2) and (3), respectively, and the maximum reductions of single pass cold-rolling without edge crack are increased from 50% of process (1) to 55% of process (2) and 62% of process (3), respectively. The plasticity improvement of the Fe–6.5wt%Si alloy can be attributed to both reductions of surface oxidation degree and order degree of the alloy by warm-rolling with gradually decreasing temperature.

Heating-cooling combined mold (HCCM) horizontal continuous casting technology developed by our research group was used to produce high axial columnar-grained CuNi10FeMn1 alloy tubes with different Fe contents. The effects of Fe content (1.08wt%–2.01wt%) on the microstructure, segregation, and flushing corrosion resistance in simulated flowing seawater as well as the mechanical properties of the alloy tubes were investigated. The results show that when the Fe content is increased from 1.08wt% to 2.01wt%, the segregation degree of Ni and Fe elements increases, and the segregation coefficient of Ni and Fe elements falls from 0.92 to 0.70 and from 0.92 to 0.63, respectively. With increasing Fe content, the corrosion rate of the alloy decreases initially and then increases. When the Fe content is 1.83wt%, the corrosion rate approaches the minimum and dense, less-defect corrosion films, which contain rich Ni and Fe elements, form on the surface of the alloy; these films effectively protect the α-matrix and reduce the corrosion rate. When the Fe content is increased from 1.08wt% to 2.01wt%, the tensile strength of the alloy tube increases from 204 MPa to 236 MPa, while the elongation to failure changes slightly about 46%, indicating the excellent workability of the CuNi10FeMn1 alloy tubes.

Three kinds of surface hardening states of the steel sheet were obtained by different mechanical surface preparation methods with flap disc and steel circumferential brushes before cold roll bonding of embedded 1060 aluminum-08Al steel composite sheets, and the influence of steel sheet surface hardening state on the interfacial bonding strength of the composite sheet and the related mechanism were studied. The results showed that numerous cracks formed between the broken work-hardened surface layer and its steel matrix during cold roll bonding, resulting in a large number of fragments at the interface, which was the main reason for the reduction of the bonding strength. It is an effective method for reducing the work-hardened surface layer hardness to improve the bonding strength of the composite sheet. The nano-hardness of the steel surface treated by flap disc was 4.5 GPa which was close to that (4.4 GPa) of the steel matrix, while the nano-hardnesses of the steel surfaces treated by the steel brushes made of Ф 0.3 mm wires and Ф 0.1 mm wires were 8.6 GPa and 5.7 GPa, respectively. For the thickness reduction of 25%, the peel strengths of the composite sheets whose original steel sheet surface were treated by the steel brush made of Ф 0.3 mm wires and Ф 0.1 mm wires were 0.9 N/mm and 2.9 N/mm, respectively, while the peel strength of the composite sheet whose steel sheet surface was treated by flap disc significantly rose to 14.9 N/mm.

•The surface morphology of double-rolled copper foil was characterized.•The morphology evolution of laminated surface in the deforming zone was observered.•The formation mechanism of matt surface was revealed.•The advantage of treating matt surface as adhesive surface was analyzed.Copper foils for flexible printed circuit boards were prepared by double rolling, and the matt surface of double-rolled copper foil was characterized by atomic force microscope, scanning electron microscope, 3D optical interferometer, optical microscope and surface profiler. The morphology characteristics of matt surface were studied, and the formation mechanism of matt surface was discussed. The results showed that the matt surface of the double-rolled copper foil presented rough and relatively homogeneous morphology, and the morphologies of upper and lower matt surfaces were practically coincident. As the copper strips just entered into the deforming zone, the roughening of laminated surface occurred, but the roughness was relatively small. When the copper strips passed through the neutral plane, the roughness of the laminated surface increased significantly. In the backward slip zone, the initial micro-dimples between the two laminated surfaces were connected in the rolling direction, which led to the formation of larger and airtight dimples; when the copper strips moved toward the neutral plane and entered into the forward slip zone, the pressure of fluid in the airtight dimples increased rapidly, which enhanced the depths of the dimples; meanwhile, the depression corrugations with certain depth and larger width were formed on the laminated surface because of the dimple connection in the width direction. The copper foils with thickness of 36–54 μm were fabricated by double rolling, and the Rz value of their matt surfaces was 1.0–1.3 μm, which meet the requirements for directly using as adhesive surface of resin substrate, and therefore multiple roughening treatments during the traditional production process of flexible printed circuit board might be omitted. The formation mechanism of the matt surface of double-rolled copper foil proposed on the basis of the metal flow and deformation mechanics theory could explain the representative characteristics of the length direction of corrugations on matt surface being perpendicular to the rolling direction, several corrugations within a grain on the matt surface and the coincident morphologies of the upper and lower matt surfaces.

•Proposed a novel approach for unambiguous identification of the plateau regime.•Found sufficient energy absorption in lotus-type porous coppers even under room-temperature impacts.•Observed strain rate independence of the energy absorption efficiency.•Observed cell wall buckling was the dominant energy absorbing mechanism.The energy absorption characteristics of the lotus-type porous coppers at the strain rate of 10–3 s–1 to ~2400 s–1 were systematically investigated. Depending on the relative density and loading rate, the energy absorption capability of the tested samples varied from ~20 to ~85 MJ m–3, while the energy absorption efficiency fluctuated around ~0.6. An energy absorption efficiency curve based approach was proposed for unambiguous identification of the plateau regime, which gave an extension of ~0.50 strain range for the presently investigated porous coppers. With detailed observations of cell wall morphologies at various deformation stages, it was suggested that buckling of cell walls was the dominant mechanism mediating the energy absorption in lotus-type porous coppers.

The effects of various structure factors on the properties (superelasticity mainly) of Cu-based shape memory alloys (SMAs) were systematically evaluated in this review article through literatures combining with our work. It is concluded that besides the decisive role of grain orientation, the grain boundary (GB) characteristics also play important roles in the superelasticity, which include GB area, GB type, GB morphology and GB direction in descending order of the effect significance. According to the above results, the prior principles of structure design are proposed for high-performance Cu-based SMAs from most to least important: (1) obtaining grain orientation with high phase transformation strain; (2) increasing grain size or reducing GB area; (3) obtaining straight low-energy GBs, especially low-angle GBs; (4) trying to make GB direction parallel to external stress. Consistent with the main or all principles, the bamboo-like-grained and columnar-grained (CG) Cu-based SMAs show excellent comprehensive properties.

The dynamic recrystallization (DRX) behavior of continuous columnar-grained (CCG) CuNi10Fe1Mn alloy was investigated by hot compression along the solidification direction (SD) and perpendicular to the solidification direction (PD). Specimens were compressed to a true strain of 0.8 at temperatures ranging from 25°C to 900°C and strain rates ranging from 0.01 to 10 s−1. The results indicate that DRX nucleation at grain boundaries (GBs) and DRX nucleation at slip bands (SBs) are the two main nucleation modes. For SD specimens, C-shaped bending and zig-zagging of the GBs occurred during hot compression, which made DRX nucleation at the GBs easier than that at the SBs. When lnZ ≤ 37.4 (Z is the Zener–Hollomon parameter), DRX can occur in SD specimens with a critical temperature for the DRX onset of ~650°C and a thermal activated energy (Q) of 313.5 kJ·mol−1. In contrast, in PD specimens, the GBs remained straight, and DRX nucleation occurred preferentially at the SBs. For PD specimens, the critical temperature is about 700°C, Q is 351.7 kJ·mol−1, and the occurrence condition of DRX is lnZ ≤ 40.1. The zig-zagging of GB morphology can significantly reduce the nucleation energy at the GBs; as a result, DRX nucleation occurs more easily in SD specimens than in PD specimens.

The effects of annealing temperature (with the annealing time being constant at 1 h) on the microstructure, ordering, residual stress, mechanical properties, and subsequent cold rolling workability of Fe-6.5wt%Si electrical steel with columnar grains were investigated, where the steel was warm rolled at 500°C with a reduction of 95%. The results show that recrystallization began to occur in the sample annealed at 575°C and that full recrystallization occurred in the sample annealed at 625°C. When the annealing temperature was 500°C or greater, the extent of reordering in the sample was high, which reduced the room-temperature plasticity. However, annealing at temperatures below 300°C did not significantly reduce the residual tensile stress on the edge of the warm rolled samples. Considering the comprehensive effects of annealing temperature on the recrystallization, reordering, residual stress, and mechanical properties of the warm rolled Fe-6.5wt%Si electrical steel with columnar grains, the appropriate annealing temperature range is 300°C-400°C. Unlike the serious edge cracks that appeared in the sample after direct cold rolling, the annealed samples could be cold rolled to a total reduction of more than 71.4% without the formation of obvious edge cracks, and bright-surface Fe-6.5wt%Si electrical steel strips with a thickness less than 0.1 mm could be fabricated by cold rolling.

The effects of deformation temperature on the microstructure, ordering and mechanical properties of Fe−6.5 wt%Si alloy with columnar grains compressed at 300–900 °C were studied. The results show that under the conditions of temperature ≤700 °C and compression reduction of 50%, the columnar grains remain intact without occurrence of recrystallization in the samples. After deformation at 800 °C, the columnar grain boundaries become serrated and subgrains form in the sample during dynamic recovery. With further increasing the temperature to 900 °C, dynamic recrystallization takes place obviously. High-density of deformation twins form in the samples deformed at 500 °C or below, while deformation twins are not observed in the samples deformed at 550 °C or above. The Fe−6.5 wt%Si alloy has the characteristic of deformation disordering and reordering at intermediate temperatures. The degree of deformation disordering is larger than that of reordering at the deformation temperature of 400–600 °C, while this relationship is opposite at 700–800 °C. At the deformation temperature lower than 700 °C, deformation resistance of the Fe−6.5 wt%Si alloy decreases drastically with the increase of the temperature, while it decreases slowly as the temperature increased to 800–900 °C. The appropriate deformation temperature of the Fe−6.5 wt%Si alloy with columnar grains is suggested at 400–700 °C.

Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10−3–2400 s−1 with the compressive direction parallel to the pores. A GLEEBLE-1500 thermal-mechanical simulation system and a split Hopkinson pressure bar (SHPB) were used to investigate the effect of strain rate on the compressive deformation behaviors of lotus-type porous copper. The influence mechanism of strain rate was also analyzed by the strain-controlling method and by high-speed photography. The results indicated that the stress-strain curves of lotus-typed porous copper consist of a linear elastic stage, a plateau stage, and a densification stage at various strain rates. At low strain rate (< 1.0 s−1), the strain rate had little influence on the stress-strain curves; but when the strain rate exceeded 1.0 s−1, it was observed to strongly affect the plateau stage, showing obvious strain-rate-hardening characteristics. Strain rate also influenced the densification initial strain. The densification initial strain at high strain rate was less than that at low strain rate. No visible inhomogeneous deformation caused by shockwaves was observed in lotus-type porous copper during high-strain-rate deformation. However, at high strain rate, the bending deformation characteristics of the pore walls obviously differed from those at low strain rate, which was the main mechanism by which the plateau stress exhibited strain-rate sensitivity when the strain rate exceeded a certain value and exhibited less densification initial strain at high strain rate.

Developing ultra-thin copper foils with different surface roughness and microstructure has important significance for improving the service performance and reducing the production cost of high-end circuit boards. In this paper, pure copper strips with initial cube texture were subjected to a double rolling process (deformation amount ranges from 50% to 95%), and the surface textures evolution law and mechanism of double-rolled strips were studied by an X-ray diffraction technique. The results show that when a deformation amount increased from 50% to 70%, the grains of two surfaces rotate away from the cube orientation, and the formed textures of two surfaces mainly consisted of C, S and B orientation components. The orientation density values for these three components on bright surface only had slight difference; the orientation density values for C and S components were much larger than that for B components on a matt surface. When the deformation amount increased to 90%, the increase extents of orientation density values for C and S components were obviously larger than that for B components on a bright surface; the increase extents of orientation density values for these three components were almost the same on the matt surface. It has been found that when deformation amount reaches 95%, the grains orientation of bright surface were relatively concentrated, and the orientation density value for C texture obviously increased to 11.68 and that for B texture was only 3.15; the grains orientation of matt surface were relatively dispersed, and the orientation density value for C texture increased to 9.26 and that for B texture obviously increased to 6.35, and the density values of these two textures had less difference. For the condition of strong compressive and shear stress on the bright surface, grains were mainly rotating to C texture orientation; compared with the bright surface, “semi-free” deformation condition on the matt surface is beneficial to promote much more grains to rotate to the B texture orientation.

Effects of boron additions on the microstructure, elemental distribution and tensile properties at an intermediate temperature of the Fe-6.5 wt.%Si alloy fabricated by directional solidification were investigated. The results showed that the undercooling degree of the liquid phase at the frontier of solid–liquid interface was increased with boron additions, leading to significant refinement of the columnar grains of the alloy. When the boron content was increased from 0 to 0.058 wt.%, the width of the columnar grains was reduced from 2157 to 514 μm. Boron facilitated to homogenize silicon in the Fe-6.5 wt.%Si alloy because the solidification segregation level of silicon was decreased due to the interaction between boron and silicon. In the same range of boron content (0–0.058 wt.%), the equilibrium partition coefficient of silicon was increased from 0.961 to 0.982. Meanwhile, both the strength and ductility of the Fe-6.5 wt.%Si alloy at 400 °C could be improved due to the boron addition. Compared with that of the alloy without boron, the ultimate tensile strength of the alloy containing 0.040 wt.% B was increased from 712 to 792 MPa and its elongation was further increased from 38.5 to 54.4%.Highlights► Adding boron can refine grains of the columnar-grained Fe-6.5 wt.%Si alloy. ► Adding boron can decrease the solidification segregation level of silicon. ► Both strength and ductility of the alloy could be improved with boron additions.

Based on horizontal continuous casting with a heating-cooling combined mold (HCCM) technology, this article investigated the effects of processing parameters on the liquid-solid interface (LSI) position and the influence of LSI position on the surface quality, microstructure, texture, and mechanical properties of a BFe10-1-1 tube (ϕ50 mm × 5 mm). HCCM efficiently improves the temperature gradient in front of the LSI. Through controlling the LSI position, the radial columnar-grained microstructure that is commonly generated by cooling mold casting can be eliminated, and the axial columnar-grained microstructure can be obtained. Under the condition of 1250°C melting and holding temperature, 1200–1250°C mold heating temperature, 50–80 mm/min mean drawing speed, and 500–700 L/h cooling water flow rate, the LSI position is located at the middle of the transition zone or near the entrance of the cooling section, and the as-cast tube not only has a strong axial columnar-grained microstructure \((\{ hkl\} < 6\bar 21 > , \{ hkl\} < 2\bar 21 > )\) due to strong axial heating conduction during solidification but also has smooth internal and external surfaces without cracks, scratches, and other macroscopic defects due to short solidified shell length and short contact length between the tube and the mold at high temperature. The elongation and tensile strength of the tube are 46.0%–47.2% and 210–221 MPa, respectively, which can be directly used for the subsequent cold-large-strain processing.

The room temperature tensile and compressive mechanical behaviors of a β1′ martensitic Cu-12 wt.% Al alloy with < 001>β1 or < 011>β1 orientation fabricated by Ohno continuous casting were investigated. An orientation-dependent tension–compression asymmetry was observed in the specimens. The various stress-induced martensite–martensite transformations were also observed in the specimens with different orientations or under different loading conditions. The anisotropy and asymmetry of mechanical behaviors of the alloy are closely related to the orientation dependence and the asymmetry of the stress-induced phase transformation. The transformation strains which were calculated based on a developed stress-induced phase transformation model and deformation mechanism of the alloy were discussed to explain the deformation behaviors.Highlights► Tension–compression asymmetry of martensitic Cu–Al alloy was observed. ► The asymmetry of stress-induced transformations was also observed. ► Deformation mechanism was discussed to explain the deformation behavior.

The tensile deformation behavior of columnar-grained Fe–6.5wt.%Si alloy with <100> fiber texture at intermediate temperatures (300–500 °C) was investigated. Compared with equiaxed-grained Fe–6.5wt.%Si alloy, the enhanced tensile ductility and its mechanism of columnar-grained Fe–6.5wt.%Si alloy were mainly studied by the analysis of tensile twinning Schmid factor value and the deformation microstructure. The results showed that tensile ductility of the Fe–6.5wt.%Si alloy with columnar grains were increased significantly, i.e., the elongation of the columnar-grained specimens were increased to 6.6% (300 °C), 51.1% (400 °C), 51.3% (500 °C), which, respectively, corresponded to an increase of 3.7%, 25.8% and 23.2% compared with that of the equiaxed-grained specimens. The analysis of tensile twinning Schmid factor value and the deformation microstructure both demonstrated that deformation twinning occurred locally in the equiaxed-grained Fe–6.5wt.%Si alloy, while a great number of twins formed homogeneously in the columnar-grained Fe–6.5wt.%Si alloy. The significant enhancement of tensile ductility of the columnar-grained Fe–6.5wt.%Si alloy at intermediate temperatures was mainly ascribed to the formation of a great number of homogeneous deformation twins.Highlights► Tensile ductility of the Fe–6.5wt.%Si alloy with columnar grains was enhanced. ► Elongation of columnar-grained specimens was 6.6%, 51.1%, 51.3% at 300, 400, 500 °C. ► Elongation of equiaxed-grained specimens was 2.9%, 25.3%, 28.1% at 300, 400, 500 °C. ► The enhancement was mainly ascribed to the formation of a large amount of twins.

Deformation twinning in coarse-grained body-centered-cubic (BCC) metals with medium to high stacking fault energy only took place during plastic deformation at low temperature or high strain rate conditions. However, in this study deformation twinning was found in an Fe-6.5 wt.% Si alloy (BCC) after intermediate temperature compression by electron backscattered diffraction and transmission electron microscope. Deformation twin with the twinning system of {1 1 2} 〈1 1 1〉 appeared in the Fe-6.5 wt.% Si alloy after compression at 400 °C, strain rate of (2–3) × 10−3 s−1 and compression amount more than 5.8%. Dislocation density inside the deformation twin was much higher than that inside the matrix and the dislocation could slip through most of twin boundary easily. It is indicated that plastic deformation of the Fe-6.5 wt.%Si alloy with columnar grains can be favorably achieved by twinning mechanism at intermediate temperature when the dislocation slip is difficult to activate. On the other hand, deformation twinning can adjust the crystallographic orientation of the grains, which is beneficial to the activation of dislocation slip.Highlights► Twinning was found firstly in Fe-6.5 wt.% Si alloy during compression at 400 °C. ► Twinning makes the grains get better orientation for activating dislocation slip. ► Dislocation density inside the twin is much higher than that inside the matrix. ► Dislocation could slip through most of twin boundary easily.

A new horizontal continuous casting method with heating-cooling combined mold (HCCM) technology was explored for fabricating high-quality thin-wall cupronickel alloy tubes used for heat exchange pipes. The microstructure and mechanical properties of BFe10 cupronickel alloy tubes fabricated by HCCM and traditional continuous casting (cooling mold casting) were comparatively investigated. The results show that the tube fabricated by HCCM has smooth internal and external surfaces without any defects, and its internal and external surface roughnesses are 0.64 μm and 0.85 μm, respectively. The tube could be used for subsequent cold processing without other treatments such as surface planning, milling and acid-washing. This indicates that HCCM can effectively reduce the process flow and improve the production efficiency of a BFe10 cupronickel alloy tube. The tube has columnar grains along its axial direction with a major casting texture of \(\left\{ {012} \right\}\left\langle {6\bar 21} \right\rangle\). Compared with cooling mold casting (δ = 36.5%), HCCM can improve elongation (δ = 46.3%) by 10% with a slight loss of strength, which indicates that HCCM remarkably improves the cold extension performance of a BFe10 cupronickel alloy tube.

Effect of γ2 phase evolution on mechanical properties of Cu–14%Al–3.8%Ni (mass fraction) alloy wires fabricated by continuous unidirectional solidification technology was investigated before and after heat treated at 700–780 °C. Mechanism for the improvement of mechanical properties of the alloy was analyzed. It was found that the alloy retained continuous columnar grains after heat treatment. With the heat treatment temperatures increasing from 700 °C to 770 °C, the coarse dendrite γ2 phase evolved into the fine polygonal, ellipsoidal and spherical particles in the grains, while the long-banding, discontinuous block and ellipsoidal particles at the grain boundaries. The average size of the γ2 phase decreased from 20 μm before heat treatment down to 2 μm, and its amount reduced from 50.0% down to 0.8%. The γ2 phase was full dissolution at 780 °C. The tensile strength of the alloy treated at 700–780 °C ranged from 577 MPa to 710 MPa. The elongation of the alloy ranged from 7.5% to 23.8% and had a peak value at 760 °C. Excellent balance between strength and elongation could be obtained when the spherical γ2 phase was distributed throughout the alloy with the size smaller than 5 μm and the amount in the range of 11.4–16.6%. The nano-hardness and elastic modulus of the γ2 phase decreased gradually with the reduction of the amount, leading to the improvement of mechanical properties.Graphical abstractThe continuous columnar-grained Cu–14 wt.%Al–3.8 wt.%Ni alloy wires before and after heat treated have distinct tensile behaviors due to the variation of the distribution, amount, size, and shape of the γ2 phase.Highlights► Plasticity of polycrystalline CuAlNi alloy can be improved by texture control. ► The γ2 phase evolution of the alloy was investigated before and after heat treated. ► Relationship between γ2 phase evolution and mechanical properties was studied. ► The alloy with some fine spherical γ2 phase had better mechanical properties. ► Reduction of the amount helps decreasing the elastic modulus of γ2 phase.

The Ohno continuous casting (OCC) process is a practical way to control the solidification texture of Cu–12 wt.%Al alloy with a perfect < 001>β fiber texture along the solidification direction. Compared with the conventional randomly oriented polycrystalline Cu–12 wt.%Al alloy, the reorientation of β1′ martensite and stress-induced phase transformation occurred at the same time within every columnar grain sharing the same [001]β orientation during tensile test, which would reduce the elastical and phase-transformational incompatibility and enhance the intergranular accommodation. As a consequence, a high tensile ductility up to 28% with transgranular fracture can be obtained for OCC columnar-grained Cu–12 wt.%Al alloy instead of intergranular fracture due to the incompatible stress at the grain boundary for randomly oriented polycrystalline Cu–12 wt.%Al alloy.

The magnetic properties of an Fe–6.5 wt.% Si alloy can be improved through texture and microstructure control during directional solidification process. With the increasing of directional solidification rate, the main texture of the Fe–6.5 wt.% Si alloy along specimen withdrawing direction evolved in the way of < 130> → < 100> → < 142>, and the coercivity initially decreased and then increased. For the directional solidification rate of 1 mm/min, a homogeneous microstructure of the Fe–6.5 wt.% Si alloy specimen with low energy boundaries between columnar grains was obtained. The main texture of the specimen was < 100>, and the coercivity of the alloy was reduced by 44% compared with that of the alloy consisting of equiaxed grains.Research highlights►Magnetic properties of Fe–6.5Si alloy can be improved by directional solidification. ►Microstructure of the alloy can be controlled by directional solidification. ►Coercivity of the directional solidified alloy was reduced by 44%. ►Low energy boundaries and < 100> fiber texture were obtained in the alloy.

Tin bronze wires were produced by dieless drawing. The effects of heating power, the distance between cooler and heater as well as feeding speed on the diameter, the temperature field, and the deformation region profile of the wires were investigated. The results indicated that each processing parameter exhibited both lower and upper limits of stable deformation based on the criterion of stable deformation with the diameter fluctuation of ±0.05 mm. Both the temperature and its gradient of the deformation region increased with increasing heating power under stable deformation, but decreased with an increase in feeding speed. As the distance between cooler and heater increased, the temperature of the deformation region increased and the slope of the deformation region profile decreased. The processing limit map of stable deformation exhibited a closed curve and the unstable deformation consisted of wire breakage and diameter fluctuations.

Copper cladding aluminum (CCA) rods with a diameter of 30 mm and a sheath thickness of 3 mm were fabricated by horizontal core-filling continuous casting (HCFC) technology. The effects of key processing parameters, such as the length of the mandrel tube of composite mold, aluminum casting temperature, flux of the secondary cooling water, and mean withdrawing speed were optimized based on some quality criteria, including the uniformity of the sheath thickness, integrality of the rods, and thickness of the interface. The causes of internal flaws formation of CCA rods were also discussed. The results showed that the continuity of the liquid aluminum core-filling process and the interface reaction control between solid copper and liquid aluminum were two key problems that strongly affected the stability of the casting process and the product quality. Our research indicated that for the CCA rod with the previously mentioned size, the optimal length of mandrel tube was 210 mm. A shorter mandrel tube allowed of easier erosion at the interface, which led to a nonuniform sheath thickness. Conversely, it tended to result in a discontinuous filling process of liquid aluminum, which causes shrinkage or cold shuts. The optimal casting temperatures of copper and aluminum were 1503 K (1230 °C) and 1043 K to 1123 K (770 °C to 850 °C), respectively. When the casting temperature of aluminum was below 1043 K (770 °C), the casting process would be discontinuous, resulting in shrinkages or cold shuts. Nevertheless, when the casting temperature of aluminum was higher than 1123 K (850 °C), a severe interface reaction between solid copper and liquid aluminum would occur. The proper flux of the secondary cooling water and the mean withdrawing speed were determined as 600 to 800 L/h and 60 to 87 mm/min, respectively. In the previously mentioned proper ranges of processing parameters, the interfacial shear strengths of CCA rods were 40.5 to 67.9 MPa.

AbstractEffects of melt temperature and casting speed on microstructure and mechanical properties of Cu-14%Al-3.8%Ni (mass fraction) alloy wires fabricated by continuous unidirectional solidification technology were investigated. It was found that the average size of columnar grain in the alloy decreased and grain boundary turned clear and straight with increasing the casting speed at a given melt temperature. When the melt temperature was up to 1 280 °C, the β1 phase gradually transformed into lozenged and lanciform γ1' martensite, as well as parallel-sided plate β1' martensite. The alloy with numerous coarsely dendritic γ2 phase has poor mechanical properties due to the difficulty of stress-induced martensitic transformation. When the amount of the γ2 phase reduced and the coarse dendrite γ2 phase evolved into the fine square particles, the elongation of the alloy increased gradually with a decrease in tensile strength. Meanwhile, the plasticity of the alloy could also be improved by increasing the amount and size of martensites, particularly the lanciform γ1' martensite. When the alloy was almost composed of coarse lanciform γ1' martensite, the tensile strength and elongation of the alloy could be up to 772 MPa and 18.9%, respectively, and the tensile curve consisted of three transformation platforms.

The back-propagation neural (BPN) network was proposed to model the relationship between the parameters of the dieless drawing process and the microstructures of the QSi3-1 silicon bronze alloy. Combined with image processing techniques, grain sizes and grain-boundary morphologies were respectively determined by the quantitative metallographic method and the fractal theory. The outcomes obtained show that the deformed microstructures exhibit typical fractal features, and the boundaries can be characterized quantitatively by fractal dimensions. With the temperature of 600–800°C and the drawing speed of 0.67–1.00 mm·s−1, either a lower temperature or a higher speed will cause a smaller grain size together with an elevated fractal dimension. The developed model can be capable for forecasting the microstructure evolution with a minimum error. The average relative errors between the predicted results and the experimental values of grain size and fractal dimension are 3.9% and 0.9%, respectively.

A reconstruction technology of finite element meshes based on reversal engineering was applied to solve mesh penetration and separation in the finite element simulation for the divergent extrusion. The 3D numerical simulation of the divergent extrusion process including the welding stage for complicated hollow sections was conducted. Based on the analysis of flowing behaviors, the flowing velocities of the alloy in portholes and near the welding planes were properly controlled through optimizing the expansion angle as well as porthole areas and positions. After the die structure optimization, defects such as warp, wrist, and the wavelike are eliminated, which improves the section-forming quality. Meanwhile, the temperature distribution in the cross section is uniform. Especially, the temperature of the C-shape notch with a larger thickness is lower than that of other regions in the cross section, which is beneficial for balancing the alloy flowing velocity.

The electromagnetic parameters and microwave absorbing properties of paraffin and polymer composites filled with glass-coated Fe69Co10Si8B13 amorphous microwire (GCFAW) were investigated. The results show that the microwire filling ratio and annealing temperature have no obvious influence on the complex permeability, while they exhibit significant effect on the complex permittivity. The complex permittivity increases remarkably with the increase of microwire filling ratio, and decreases sharply with increasing the annealing temperature. With the increase of microwire filling ratio and absorber thickness, the minimum reflection loss decreases firstly and then increases, and shifts towards lower frequency region. For the paraffin composite with GCFAW filling ratio of 15% and thickness of 1.4 mm, the minimum reflection loss is −28.5 dB and the frequency bandwidth less than −10 dB is 2.9 GHz. When the microwire filling ratio and the thickness of paraffin composite are invariant, the frequency of minimum reflection loss shifts towards higher region with increasing the annealing temperature. The change trend of measured reflection loss of polymer composite is consistent with that of calculation reflection loss of paraffin composite, but the minimum reflection loss increases a little and shifts towards lower frequency. As the microwire filling ratio is 15%, the reflection loss of polymer composite exhibits two extreme values.

In this paper, a novel safe and high-efficient fabrication processing named in-situ reaction and unidirectional solidification method was presented for lotus-type porous metals. The fabrication process of lotus-type porous magnesium by the in-situ reaction method had been investigated, and the rule of effect of processing parameters on pore structure and porosity was analyzed. The results showed that the porosity of the samples fabricated under different processes conditions had a wide range from 2.4 percent to 54.2 percent. The content of water, the addition of powder, the solidification rate, and casting temperature all had significant effect on the porosity and pore structure. The porosity of the samples increased with increase of the content of water, addition of powder or the solidification rate. But increasing the casting temperature would make the porosity of samples first increase then decrease. The pore in sample fabricated by in-situ reaction and unidirectional solidification method was round and regular, pore wall was very smooth, distribution of pore size was relatively uniform, and the pore growth direction was parallel to solidification.

For extrusion of hollow profile with asymmetric cross-section, existing FEM software cannot simulate the influence of divergent and welding on the metal flowing behaviors, because it is inability to deal with meshes separation and penetration during welding. A mesh-reconstruction technology based on the reverse engineering is proposed in this paper, and extrusions of Al-alloy hollow profiles with various cross-sections are simulated. The results show that the mesh-reconstruction technology can solve the problem of simulation termination caused by the meshes separation and penetration during porthole die extrusion. It is effective to analyze the metal flowing behaviors, temperature distribution, hydrostatic stress in weld-chamber, and stress on dies, which provides a practicable way for die structure design and optimization of porthole extrusion as well as quality forecast of extrusion products.