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Aluminum alloys with ultra-strength and high-toughness are fundamental structural materials applied in the aerospace industry. Due to the intrinsic restriction between strength and toughness, optimizing a desirable combination of these conflicting properties is always challenging in material development. In this study, 171 sets of data were curated based on the characteristics of high-strength and high-toughness aluminum alloys in the literature. Then, a machine learning design system (MLDS) with a property-oriented design strategy was established to rapidly discover novel aluminum alloys with ductility and toughness indexes (with elongation δ=8%–10% and fracture toughness KIC=33–35 MPa·m1/2) comparable to those of current state-of-the-art AA7136 aluminum alloys when the ultimate tensile strength (UTS) exceeded approximately 100 MPa, with values reaching 700–750 MPa. With the MLDS for experimental verification, three typical candidate alloys show satisfactory performance with UTS of 707–736 MPa, δ of 7.8%–9.5%, and KIC of 32.2–33.9 MPa·m1/2. The high contents of Mg and Zn alloying elements in the novel alloys form abundant η′ phases, which produce a significant hardening effect, while the reasonable matching of Cr, Mn, Ti and Zr dispersoids refines the grain size. The decreased Cu content compared with that in the AA7136 alloy inhibits the formation of the σ phase and S phase, so that the alloys show high toughness.

The role of Cr in affecting the precipitates and the properties of aged Cu−Cr−P alloys was investigated and discussed. The results show that there are mainly three sizes of Cr phase in aged Cu−Cr−P alloys, among them, the nano-sized Cr phase plays an important role in the strength of Cu−Cr−P alloys. The strengthening effect of Cr phase (less than 5 nm) with FCC structure completely coherent with the matrix is calculated to be about 200 MPa on the basis of dislocation cut-through mechanism. The strengthening effect of Cr phase (10−20 nm) with BCC structure incoherent with the matrix is calculated to be about 100 MPa on the basis of the Orowan dislocation bypass mechanism. The increase of Cr content changes the number and size of nano-sized Cr phase, which causes the mechanical properties of the Cu−Cr−P alloys to increase first and then decrease. The tensile strength of Cu−0.36Cr−0.01P alloy is 572 MPa and its electrical conductivity is 80% IACS after solid solution treatment at 980 °C for 2 h followed by 95% cold rolling and then aging treatment at 450 °C for 1 h.

Generally, μ phase preferentially precipitates at the place where the refractory elements segregate. However, in this study, the μ phase preferentially formed in the interdendritic regions of Co-Ni-Al-W-based superalloys during solution treatment, while the refractory elements W and Cr segregate to the dendritic cores. The microstructure evolution of the alloy during solution treatment was investigated. It showed that three different mechanisms caused this abnormal precipitation in the interdendritic regions, including primary carbides degeneration, further degeneration of the secondary carbides formed by the Laves phase decomposition, and direct precipitation from the interdendritic regions induced by the Laves phase decomposition.

Cu-0.36wt.%Be-0.46wt.%Co alloy plate with 300 mm in width and 10 mm in thickness prepared by heating-cooling combined mold (HCCM) horizontal continuous casting was cold rolled. Microstructure evolution and mechanical properties of the alloy as well as its deformation mechanism were investigated. The results showed that the as-cast alloy plate had columnar grains along the length direction, good surface quality and elongation of 35%, which was directly large-reduction cold rolled without surface treatment, and the accumulative cold rolling reduction reached 98%. When the reduction was small (20%), numerous dislocations and dislocation cells formed, and the deformation mechanism was dislocation slip. When the reduction was 40%, deformation twins appeared, and interactions between twins and dislocation cells induced strip-like dislocation cells. When the reduction exceeded 60%, shear bands formed and apparent crystal rotation in the micro-region happened. Further increasing the reduction, the amount of the shear bands rose and they interacted with each other, which refined the grains apparently. The tensile strength and hardness increased from 353 MPa and HV 119 of the as-cast alloy to 625 MPa and HV 208 with 95% reduction, respectively, and the elongation reduced from 35% to 7.6%. A process of HCCM horizontal continuous casting-cold rolling can work as a novel compact method to fabricate Cu-Be alloy sheet.

Two different thermo-mechanical processing routes, single-cold-rolling and double-cold-rolling, are adopted to process a Cu-Ni-Si alloy, and their effects on the microstructure and properties of the alloys are investigated. While keeping identical aging treatments and equivalent total cold-rolling deformation, 45-minute final aging at 450 °C endows the double-cold-rolling-processed alloys with a tensile strength of 754 ± 12 MPa, higher than 691 ± 3 MPa for the single-cold-rolling-processed alloys, whereas their electrical conductivities are close (~ 39 pct IACS). The final aging at 450 °C for 4 hours, on the other hand, renders the double-cold-rolling-processed alloy an electrical conductivity of 52.6 pct IACS, greater than 43.7 pct IACS for the single-cold-rolling-processed alloy, whereas their strengths are approximately identical (~ 705 MPa). The superior mechanical and electrical properties in the double-cold-rolling-processed alloy with the final aging time from 45 minutes to 4 hours are attributed to the dissolution of large precipitates during the second cold rolling followed by the acceleration of fine and uniformly dispersed precipitates in the final aging. Finally, the effects of dislocations, grain boundaries, solute atoms, and precipitates on the mechanical and electrical properties of the examined Cu-Ni-Si alloy are discussed on the theoretical basis, which can provide guidelines to further processing optimization.

The microstructure and mechanical properties of Co-Al-W to Co-Al-Mo/Nb alloy systems have been investigated in an attempt to identify the influence of replacement for W in multicomponent Co-based alloys with 30 at. pct Ni and 12 at. pct Cr. Either Mo or Nb additions at the expense of W reduce alloy density to a similar extent. Increasing Mo substitution significantly decreases the γ′ volume fraction and results in spherical γ′ morphology at 750 °C, whereas Nb substitution shows opposite effects on the γ′ volume fraction and morphology. Accordingly, the Mo and Nb additions raise and decrease the microhardness and high-temperature compression strength, respectively. The results can provide reference for the development of Co-based superalloys with low density and high strength.

The inhomogeneous deformation behavior generated by deformability differences between soft and hard phases is a critical factor that influences the deformation and processability of materials. For Fe-6.5pctSi alloys with coexisting disordered and ordered phases, this work studied warm (300 °C to 500 °C) tensile deformation property differences and mechanisms for non-Ce-doped and 0.02 wt pct Ce-doped alloys. The warm deformation behavior was analyzed according to the stress and strain partitioning of the two-phase alloy by establishing a two-phase (A2 disordered phase + B2/D03 ordered phase) system model based on the structural characteristics of the alloy. The results show that the plastic deformation is mainly attributed to the A2 disordered phase, and the existence of a hard and ordered phase leads to local and inhomogeneous deformation behavior, which decreases the uniform plastic elongation and deformability of the alloy. Ce doping improves the warm deformation homogeneity and deformability by reducing the size and amount of the B2 ordered phase, which improves the warm rolling deformation and increases subsequent cold rolling deformability. Cold rolling with a total thickness reduction greater than 63 pct was achieved after the Ce-doped hot-rolled specimen with a 2 mm thickness was warm rolled to an 82.5 pct reduction, and the warm-rolled and cold-rolled sheets had good surface integrity and no obvious cracking.

Heating-cooling combined mold (HCCM) horizontal continuous casting was used to produce Ф70 mm × 3.5 mm CuNi10Fe1.8Mn1 alloy tubes. The as-cast tube had good surface quality, strong axial columnar grains and high elongation to failure of 45%, and can be directly drawn without surface treatment. The maximum cumulative cold deformation amount reached 94%. For the small deformation amount (

A process of heating-cooling combined mold horizontal continuous casting→cold rolling→solid-solution treatment was used to produce Cu-1.7 wt% Be alloy sheet, and the precipitation behavior, microstructure and properties of the Cu-1.7 wt% Be alloy sheet during aging were investigated. The results showed that the phase transformation sequence of the alloy during aging at 325 °C was GP zone→γ″→γ′→γ equilibrium phase. The reasonable aging parameters were aging temperature of 325 °C and aging time of 3 h, and the hardness, tensile strength and yield strength of the aged alloy reached the peak values of 375 HV, 1042 MPa and 778 MPa, which were 172%, 116%, and 255% higher than those of the solid-solution alloy, respectively, and the electrical conductivity was 22.4% IACS. The formation of a large number of dispersed nano-sized γ′ phase was mainly responsible for the high strength of the alloy. A dynamic model of aging precipitation was established and the yield strength of the peak-aged alloy was calculated by the strengthening model. The deviation of the calculated value (797 MPa) and the measured value (778 MPa) was 2.4%, and the strengthening mechanism of the peak-aged alloy was determined as the Orowan bypass mechanism.

C70250 (Cu-2.6 wt%Ni-0.5 wt%Si) alloy plates with straight columnar grains, inclined columnar grains and equiaxed grains were produced by a heating-cooling combined mold (HCCM) horizontal continuous casting, respectively, and the influences of microstructure on the mechanical properties of the alloy were studied. The results showed that, when the casting speed was 30 mm/min, the straight columnar grains along the casting direction formed in the C70250 alloy plate and the precipitate content was relatively high, ～ 10%. When the casting speed was 50 mm/min and 80 mm/min, inclined columnar grains and equiaxed grains formed, respectively, with a low precipitate content of 6%. The high casting speed made the solid-liquid interface at the entrance of the cold mold and the solidified plate was cooled rapidly due to strong cooling effect, which suppressed formation of precipitated phase. The yield strength of the alloy plate with equiaxed grains were 219 MPa and the elongation to failure was 36%. For the plate with inclined columnar grains, its yield strength (76 MPa) were obviously lower than that of the other two plates and the elongation reached 45%. Compared with the equiaxed grain plate, the columnar grain plate had smaller grain orientation difference, better intergranular deformation compatibility and intergranular deformation uniformity, which was mainly responsible for its better plasticity.

Topologically close-packed (TCP) phases such as μ and Laves phases formed during solidification has an important influence on the mechanical properties of superalloys. Understanding the formation and elimination mechanism of TCP phases is the key to promote the development of superalloys. In this study, C15-Laves phase was first found in a Hf-containing Co-based superalloy, meanwhile, the formation mechanism and thermal stability of the C15-Laves phase were clarified. The results showed that the formation of C15-Laves phase was associated with the segregation behavior of alloying elements during solidification: Co, W and Cr segregated to the dendrite core, and Hf, Ta, Ti, Mo, Ni, Al, Si segregated to the interdendritic region. In the final stage of solidification, the C15-Laves phase enriched in Hf, Ta and Ti formed, and it had similar lattice parameters to the C15-Co2Hf phase. The incipient melting point of C15-Laves phase was between 1170 ℃ and 1180 ℃, and it gradually decomposed to form the Hf-rich MC carbide during solution treatment. The large formation energy differences between the MC carbide and C15-Laves phase promoted a rapid elimination of the C15-Laves phase, which reduced solution treatment time of the alloy. The results can provide a theoretical basis and experimental data support for the composition design and heat treatment process optimization of multicomponent novel Co-based superalloys.

Five novel Co-30Ni-(6+x)Al-(3-y)W-yMo-1Ta-3.5Ti-12Cr-0.1Hf-0.025 C (x = 0, y = 0, 1, and x = 2, y = 0, 1, 2 at%) multi-component polycrystalline γ′-strengthened Co-base superalloys are designed to investigate the effects of Al and Mo content on the microstructure and properties in this study. Based on the 6Al3W alloy, the addition of 2 at% Al has the effects of increasing the γ′ solvus temperature, reducing the density, increasing the γ′ volume fraction and coarsening rate, reducing the Vickers hardness but increasing the yield strength at 750 ℃. The replacement of 1 at% W by 1 at% Mo remarkably reduced the density with a negligible effect on the γ′ coarsening rate; Meanwhile, this slightly reduced the γ′ solvus temperature and volume fraction causing a slight decrease of Vickers hardness and yield strength at 750 ℃. The experimental alloys all show relatively low density, large processing window, good microstructure stability at 750 ℃ and mechanical properties, especially for 6Al2W1Mo alloy which has density of 8.69 g cm−3, processing window of 247 ℃, room-temperature Vickers hardness of 5.1 GPa, stable microstructure without detrimental phase after a heat treatment of 900 ℃ @8 h+ 750 ℃ @1000 h. These results may provide guidance for the development of the novel wrought Co-base superalloys with high performance and low density.

The effects of Ta and Ti on the microstructure, segregation and solidification path of Co-7Al-8W-base alloy were investigated using directional solidification quenching experiments and isothermal solidification quenching experiments. The results showed that the as-cast microstructure of the Co-7Al-8W alloy (Base alloy) is the γ single phase. The Al element slightly segregates to the interdendritic regions, the W element slightly segregates to the dendritic core, and Co has almost no segregation. The solidification path of the Co-7Al-8W alloy is L→L1+γ→γ. With the addition of 1 at.% Ta, there is no change in the segregation of elements, the microstructure and the solidification path of the alloy. The Ta element strongly segregates to the interdendritic regions in the Co-7Al-8W-1Ta alloy. With the addition of 4 at.% Ti, the Ti element strongly segregates to the interdendritic regions, and the segregation of Al and W elements increases. Blocky γ′ phase and (β+γ′)e eutectics form in the interdendritic regions. The solidification path of the Co-7Al-8W-4Ti alloy is L→L1+γ→L2+γ+(β+γ′)e→L3+γ+(β+γ′)e+γ'→γ+(β+γ′)e+γ'. After the addition of 1 at.% Ta+4 at.% Ti, the segregation of Al, Ta and Ti decreases, while the segregation of W increases. Laves phase, blocky γ′ phase and (β+γ′)e eutectics form in the interdendritic regions. The solidification path of the Co-7Al-8W-1Ta-4Ti alloy is L→L1+γ→L2+γ+Laves→L3+γ+Laves+(β+γ′)e→L4+γ+Laves+(β+γ′)e+γ'→γ+Laves+(β+γ′)e+γ'. The above results could provide an experimental basis for composition optimization and solidification process control of novel γ′-strengthened Co-base superalloys.

Continuous columnar-grained Cu-Ag alloy bars containing different silver contents (6 wt%, 12 wt%, 24 wt%) with diameters of 10 mm were prepared by directional solidification technology firstly and drawn to 0.3 mm directly at room temperature without intermediate annealing in this study. With incremental Ag contents, eutectic microstructure distributed in the interdendritic region which parallel to the casting direction grew with a higher tensile strength but almost invariable elongation and electrical conductivity of the alloys. Meanwhile, the tensile strength of the alloy wires were enhanced greatly with increasing drawing strains owing to the remarkable fiber reinforcement effect, whereas the elongation and electrical conductivity decreased slowly. With the increase of drawing strains, columnar grains and eutectic phases were drawn into dense microcomposite structure, and the volume fraction of texture in Cu and Ag phases increased in the three experimental alloys; while, the growth rate of texture in Ag phases was lower than that in Cu phases, which is one of the main reasons for the excellent ductility of the alloys. These results may offer reference for the choice of Ag content and drawing strain, and then developing a short preparation process of Cu-Ag alloys with directional solidification + drawing (without intermediate annealing).

The V-Ti-N microalloyed steel with a carbon content gradient was innovatively obtained through surface decarburization. Then, the effect of carbon contents on intragranular ferrite (IGF) formation was studied. With the carbon contents increasing from 0.39% to 0.47% (mass percent), the volume fraction of IGF decreases from 8.2% to 4.6%, but the number of IGF has no significant change. The critical size of IGF nuclei was calculated on the basis of classic heterogeneous nucleation theory. According to the results of calculation and statistics, with the carbon content increasing from 0.39% to 0.47%, the number of IGF nuclei does not decrease significantly. When the carbon content is relatively low, some (Ti, V)(C, N) particles precipitating in austenite matrix may also act as the nuclei of IGF to refine the pearlite-ferrite microstructure.

Effect of Ag addition on the microstructure and mechanical properties of as-cast, cold-rolled and aging treated Cu-Cr alloys were investigated in this study. The results indicated that adding a small amount of Ag significantly improve the mechanical properties of the Cu-Cr alloys with little effect on electrical conductivity. Besides the solution strengthening mechanism of Ag, the distribution changes of Cr precipitates from the chain along grain and dendritic boundaries to homogeneously dispersed sphere in the as-cast Cu-Cr-Ag alloys, and more fibrous Cr precipitates obtained in the cold-rolled Cu-Cr-Ag alloys also played key roles in the performance improvement of the alloys. By intermediate frequency induction melting with non-vacuum melting condition, 1000 °C − 60 min solution treatment, 95% cold-rolling deformation, and 400 °C − 90 min aging treatment, the Cu-0.89Cr-0.44Ag alloy exhibited excellent mechanical-electrical properties with the tensile strength of 541.5 MPa and electrical conductivity of 83.2%IACS. Meanwhile, the Cu-0.94Cr-0.11Ag alloy showed a better cost performance (tensile strength*conductivity/raw material price per kg) about 800 MPa*%IACS/Yuan. These relevant results provided important references for research and development of the high-performance Cu-Cr-Ag alloy.

Effect of the addition of trace HA particles into Mg-2Zn-0.5Sr on microstructure, mechanical properties, and bio-corrosion behavior was investigated in comparison with pure Mg. Microstructures of the Mg-2Zn-0.5Sr- x HA composites ( x = 0, 0.1 and 0.3 wt%) were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). Results of tensile tests at room temperature show that yield strength (YS) of Mg-2Zn-0.5Sr/HA composites increases significantly, but the ultimate tensile strength (UTS) and elongation decrease with the addition of HA particles from 0 up to 0.3 wt%. Bio-corrosion behavior was investigated by immersion tests and electrochemical tests. Electrochemical tests show that corrosion potential ( E corr ) of Mg-2Zn-0.5Sr/HA composites significantly shifts toward nobler direction from −1724 to −1660 mV SCE and the corrosion current density decreases from 479.8 to 280.8 μA cm −2 with the addition of HA particles. Immersion tests show that average corrosion rate of Mg-2Zn-0.5Sr/HA composites decreases from 11.7 to 9.1 mm/year with the addition of HA particles from 0 wt% up to 0.3 wt%. Both microstructure and mechanical properties can be attributed to grain refinement and mechanical bonding of HA particles with second phases and α-Mg matrix. Bio-corrosion behavior can be attributed to grain refinement and the formation of a stable and dense CaHPO 4 protective film due to the adsorption of Ca 2+ on HA particles. Our analysis shows that the Mg-2Zn-0.5Sr/0.3HA with good strength and corrosion resistance can be a good material candidate for biomedical applications.

The morphology of the second phases formed during the solidification is irregular in many alloy systems, making precise simulation of their dissolved evolution difficult. In this work, a multi-particle spherical log-normal distribution was used to simulate the dissolution of such irregular second phase and took the as-cast Cu-Ti alloy as a case study. The dissolution of the as-cast Cu4Ti phase was simulated via a multi-particle dissolution model integrating the CALPHAD-based diffusion theory (CALPHAD: CALculation of PHAse Diagrams) and high-throughput calculations. The 5041 sub-models (spherical log-normal distributions) replacing the size distribution of the as-cast Cu4Ti phase were initially generated based on the mass balance. Then, 2.5 × 10 6 data points in 491 sub-models selected from 5041 sub-models were calculated to fit the experimental DSC curves based on the energy conservation, and the best-fitted sub-model could be determined finally. Based on this sub-model, the volumetric and energetic evolution of the as-cast Cu4Ti phase during various dissolution processes could be predicted, and the simulated results were confirmed to be in agreement with the present experimental results. Also, a counterintuitive self-coarsening phenomenon of the Cu4Ti phase has been observed during heating, which has been approved in the experimental work.

Optimizing the composition and improving the conflicting mechanical and electrical properties of multiple complex alloys has always been difficult by traditional trial-and-error methods. Here we propose a machine learning strategy to design alloys with remarkable properties by screening key alloy factors through correlation screening, recursive elimination and exhaustive screening, and then designing composition iteratively through Bayesian optimization. Taking the precipitation strengthened copper alloys as an example, 5 kinds of key alloy factors affecting hardness (HV) and 6 kinds of key alloy factors affecting electrical conductivity (EC) were obtained by screening alloy factors. “HV - key alloy factors” model with error less than 7% and the “EC - key alloy factors” model with error less than 9% were established, respectively. Then, new copper alloys were effectively designed utilizing Bayesian optimization and iterative optimization experiments. Designed Cu-1.3Ni-1.4Co-0.56Si-0.03Mg alloy has excellent combined mechanical and electrical properties with the measured ultimate tensile strength (UTS) of 858 MPa and EC of 47.6%IACS. The property results are superior to the reported precipitation strengthened copper alloys, which realize the simultaneous improvement of the conflicting mechanical and electrical properties.

We prepared samples with different ferrite-pearlite characteristics and deformation by heat treatment and Gleeble thermocompression respectively. Then, the different samples are rapidly heated to 1200 °C for 60 s to study the austenite grain growth. The study results show that the ferrite-pearlite characteristics has little effect on austenite grain growth. With the mean austenite grain size (MAGS) of billet microstructure increasing from 14 µm to 56 µm, the MAGS after heating only increases from 47 µm to 56 µm. With the cooling rate of billet samples increasing from 0.1 °C/s to 1.0 °C/s, the MAGS after heating has basically no change. However, the deformation of billet samples has significant effect on the austenite grain growth. With the deformation at 1150 °C increasing from 10% to 50%, the MAGS after heating decreases from 63 µm to 31 µm. In the meanwhile, the mean distance between element segregation bands decreases from 115 µm to 33 µm, and the mean width of element segregation bands decreases from 70 µm to 20 µm. Electron probe microanalysis shows that the segregation region has higher Si, Cr, Mn and V contents, which generate stronger solute drag effect on austenite grain boundaries. Deformation can crush the as-cast grains and make the segregation bands fine and dispersed, further refining the austenite grains after heating.

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.

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 Cu 4 Zr 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.

The effects of rolling and heat treatment on the microstructure and superelasticity of columnar-grained Cu 71 Al 18 Mn 11 shape memory alloy were investigated in this paper. Two different rolling strategies were adopted: (i) multipass high-temperature rolling (HR); (ii) one-pass HR followed by several-pass cold rolling (HR+ n CR). For the first rolling strategy, the results showed that columnar-grained microstructure was reserved after one-pass HR at 800 °C with rolling reduction of above 80%, and recrystallization would occur if more HR processes were applied. The superelastic strain could reach 5.9% in multipass HR sample through microstructure control by annealing at 800 °C. For the second rolling strategy, after the first pass HR with the reduction of 80% and annealing at 550 °C, the alloy could be cold rolled at room temperature with total reduction of 50–70%. The columnar-grained microstructure still existed in the cold-rolled alloy which consisted of two phases (i.e. β 1 +α). After recrystallization annealing, the HR+ n CR alloy tend to form texture along the rolling direction, which was helpful to obtain high superelasticity. Finally, the grain growth heat treatment was used to further improve the superelasticity of the cold-rolled alloy. After 2–3 times abnormal grain growth heat treatment, the grains of the alloy could grow up from several hundred micrometers to more than one centimeter in diameter; they still had strong texture along the rolling direction, which enabled the superelastic strain of as high as about 7%.

Columnar-grained QSn6. 5-0. 1 alloy slabs with a width of 70 mm and thickness of 10 mm were fabricated by heating-cooling combined mold (HCCM) horizontal continuous casting. The effects of process parameters on solidification microstructure, surface quality, composition segregation and mechanical properties were studied. The results showed that the slabs with good surface quality, excellent mechanical properties and no obvious segregation could be prepared at the melt casting temperature of 1 250 °C, the heating-mold temperature of 1150–1200 °C, the cooling water flow rate of 600 L/h and the casting speed of 20–80 mm/min. The slabs had the yield strength of 124–155 MPa, the elongation rate of 46.6%–56.3% and the surface roughness of 0.22–0.55 µm, which enabled them to be directly processed without subsequent milling surface. The ratio of Sn content in the surface to that in the core was 0.83–1.10, with an average value close to 1.0, and not obviously influenced by process parameters. When the casting speed increased from 20 to 80 mm/min, the grain size changed little if the other process parameters were the same. When the heating-mold temperature increased from 1150 to 1 200 °C, the grain size was obviously refined and became more uniform if the casting speed was the same. Within the range of the casting speed at which the columnar grain structure could be obtained, the columnar grain size was mainly influenced by the heating-mold temperature.

In this work, the influence of different Ti additions on microstructure and property in Cu-Cr alloys has been studied and the primary relationship of processing-microstructure-property in Cu-Cr-Ti alloy has been constructed via the CALPHAD-based Integrated Computational Materials Engineering (ICME) approach and experimental validation. The peak-aged Cu-0.5Cr-0.2Ti alloy offers an excellent combination of hardness 192.6 HV, tensile strength 629.3 MPa, yield strength 603.0 MPa, electrical conductivity 51.3 %IACS and elongation 10.9 %. The calculated results suggest that the addition of Ti could promote the nucleation and hinder the growth of Cr precipitate in Cu-Cr-Ti alloys during aging treatment, which may promote the homogeneous formation of small-size precipitate Cr and improve the strength of the Cu-Cr alloy. Microstructural characterization has validated the calculation results and revealed that the exceptional properties of this alloy are mainly attributed to nano-scale Cr precipitates achieved through the optimal thermomechanical processing from present ICME. Thus, the present ICME flowchart is applicable to design alloy composition and optimize the processing for the desired microstructure and property in engineering industries.

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 corner and a compressive orientation near the – 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 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.

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.

The evolution of cold-rolling and recrystallization textures in the newly-developed ferrous shape memory alloy (FeNiCoAlNbB) was investigated and the improving mechanism on superelasticy of the severe cold-rolled alloy was discussed. A weaker copper rolling texture ({112}〈111〉) was formed in FeNiCoAlNbB alloy at relatively low rolling reductions (≤80%); the copper rolling texture transformed to the Goss {110}〈001〉 and brass {110}〈112〉 orientations through twinning and dislocation slipping with the rolling reductions of 90%–95%; significantly enhanced rolling texture of a strong brass orientation was obtained with the rolling reduction of 98.5%. The 98.5% cold-rolled FeNiCoAlNbB alloy after solution treatment at 1220 °C for 1 h with strong {hk0}〈001〉 recrystallization texture, followed by aging for 96 h at 600 °C exhibited good superelasticity of 3.2% with residual strain only 0.7%, and the tensile strength was approximately 960 MPa. Compared with the non-superelasticity in the as-forged FeNiCoAlNbB alloy, the considerably improving superelasticity in this alloy mainly attributes to the formation of strong favorable textures and the suppression of grain boundary precipitation.

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.

Deformation behaviors and mechanisms under different temperatures for columnar-grained Fe-6.5Si (mass%) alloys fabricated by directional solidification and equiaxed-grained Fe-6.5Si alloy fabricated by forging were comparatively investigated. The results showed that, with increasing the deformation temperature from 300 °C to 500 °C, the elongation increased from 2.9% to 30.1% for the equiaxed-grained Fe-6.5Si alloy, while from 6.6% to about 51% for the columnar-grained Fe-6.5Si alloy. The deformation mode of equiaxed-grained Fe-6.5Si alloy transferred from nearly negligible plastic deformation to large plastic deformation dominated by dislocation slipping. Comparatively, the deformation mode of the columnar-grained alloy transferred from nearly negligible plastic deformation to plastic deformation dominated by the twining, and finally to plastic deformation dominated by dislocation slipping. Meanwhile, compared with the alloy with equiaxed grains, it was found that ultimate tensile strength and elongation could be increased simultaneously, which was ascribed for the twinning deformation in columnar-grained Fe-6.5Si alloy. This work would assist us to further understand the plastic deformation mechanism of Fe-6.5Si alloy and provide more clues for high-efficiency production of the alloy.

Micro-deformation behavior and mechanical properties of columnar-grained Fe-6. 5 mass%Si alloy before and after warm rolling were investigated by means of micro-indentation and three-point bending tests. The results show that the columnar-grained Fe-6. 5 mass%Si alloy before warm rolling presents sink-in mode of micro-indentation, while pile-up mode with a number of arc-shaped deformation bands exists in the warm-rolled alloy. Compared with that of the alloy before warm rolling, the maximum bending fracture stress and maximum bending fracture deflection of the warm-rolled alloy are increased by 96% and 50%, respectively. The different micro-deformation behavior and mechanical properties of the columnar-grained Fe-6. 5 mass%Si alloy are ascribed to the changes of dislocation density, dislocation configuration and long-range order degree, which significantly improve the room temperature plasticity of the alloy after warm rolling.

Cold rolled sheets of high silicon electrical steel (Fe-6.5 wt% Si alloy) with thicknesses of 0.2–0.4 mm were fabricated by directional solidification and rolling, and the microstructure, texture and magnetic properties of the sheets annealed at 700–1300 °C for 1 h were investigated. The roles of recrystallization texture and grain size in influencing the magnetic induction and core loss were clarified. All the samples had strong {100} recrystallization texture with volume fraction of 18.3–47.3% and exhibited high magnetic induction and low core loss. For the samples with a thickness of 0.2 mm after annealing at 800–1200 °C, the magnetic induction B8 and the core loss P10/50 reached 1.273–1.378 T and 0.49–0.84 W/kg, respectively. The grain size played a much more important role in the core loss than recrystallization texture. The average grain size to seek minimum core loss P10/50 was 536–615 μm in the high silicon electrical steel sheets with thicknesses of 0.2–0.4 mm, which was larger than 100–200 μm for the electrical steel with common silicon content. The magnetic induction B8 of the samples improved with an enhancement of {100} recrystallization texture, but reduced with an increase of average grain size. The effect of recrystallization texture on the magnetic induction B8 was much greater than that of grain size.

Texture evolutions and recrystallization texture features in warm- and cold-rolled sheets of high silicon electrical steel with two different initial microstructures (columnar-grained and equiaxed-grained microstructures) were investigated. The relationships between the recrystallization textures and the initial textures (the textures before rolling) of the samples were analyzed. The results showed that after annealing at 1073 K (800 °C) for 1 hour, strong {100} recrystallization textures with volume fractions of more than 47 pct were obtained in the columnar-grained samples fabricated by warm and cold rolling along the growing direction of the columnar grains. While after rolling and annealing in the same processes, only 12.8 pct volume fractions of {100} recrystallization texture were revealed in the equiaxed-grained samples. The formation of strong {100} recrystallization texture in the annealed sheets of high silicon electrical steel with initial columnar grains was attributed to the favorable texture inheritance of the initial texture during rolling and annealing. The columnar grains of strong near {100}〈001〉 ({100}〈001〉 ~ {310}〈001〉) orientation in the samples before rolling were transferred into deformed grains with orientations such as {100}〈011〉 and {100}〈012〉. after rolling. Afterwards, these deformed grains were further transferred into {100} oriented recrystallized grains, which formed strong {100} recrystallization texture in the annealed sheets and exhibited preferable soft magnetic properties.

Outstanding ductility of Fe-6.5 wt%Si alloy can be obtained in a wide deformation rate range (1–125×10 −4 s −1 ) due to the ultra-low deformation rate sensitivity of the columnar-grained alloy with 〈100〉 orientation deformed at 400 °C. This finding provides a high-efficiency approach to prepare Fe-6.5 wt%Si alloy and a guideline for microstructure control.

Effects of rare earth RE (Y, La, Ce) element doping on electronic structure of Fe-6.5 wt%Si alloy and the influence mechanisms of RE doping on mechanical properties of the alloy were studied via first-principles calculation based on density functional theory (DFT). The results show that there exists significant electron transfer between solid solution RE atom and Fe, Si atoms, which leads to a significant change on the gain/loss quantity of electrons and the bonding properties of atoms, thus changing the covalent interaction of Fe–Fe bonds and Si–Fe bonds, reducing the ordered degree and improving the deformability of Fe-6.5 wt%Si alloy. With an increase of RE content, the tensile deformability at 400 °C of as-cast alloy specimens presented a change rule of first increasing and then decreasing, and the elongation to failure increased from about 7% of non-RE-doped specimens to a maximum of about 22–23% of RE doped specimens. The content of Y, La, and Ce is about 59 ppm, 38 ppm, and 75 ppm respectively (atom fraction, called reasonable content) when the deformability improvement effect of RE is better, the RE exceeding reasonable content tended to enrich near grain boundaries and caused inter-granular brittleness. Through a comparative study between non-RE-doped alloy and RE (Ce) doped alloy, it was found that there was no significant difference in microstructure and crystal structure between the warm-rolled samples of two alloys, but Ce doping reduced tensile yield strength σ0.2 from 1618.5 MPa to 1515.3 MPa and increased elongation to failure from 0.67% to 0.80% at room temperature of warm-rolled samples by weakening covalent interaction of some bonds, which helps to improve cold rolling deformability of samples, and Ce doping caused no obvious damage to magnetic properties of the thin sheet after cold rolled.

Fe-6.5 wt% Si alloy (high silicon electrical steel) is an ideal core material for making motors and transformers with low noise and low power loss. Controlling microstructure and texture is key to improving the magnetic properties of high silicon electrical steel. In order to improve the warm rolling and cold rolling workability of high silicon electrical steel, in this paper, 0.03 wt% Nb is added to the alloy, and a strip sample with a thickness of 0.13 mm was prepared. The effect of annealing temperature on microstructure, texture and magnetic properties of the samples was studied. The results show that annealing at 800 ℃–1300 ℃ for 1 h, with the increase of annealing temperature, the {1 0 0} texture content of the sample decreased from 9.47% to 1.09%, {1 1 0} texture content gradually increased from 1.26% to 33.1%, {1 0 0}+{1 1 0} texture content increased significantly from 10.73% to 34.19%. Nb-rich precipitates are formed in high silicon electrical steel with a size of about 100 nm. When the annealing temperature is lower than 1200 ℃, the Nb-rich precipitates can inhibit the grain growth. When the annealing temperature is higher than 1200℃, the Nb-rich precipitates dissolves and the pinning force to the grain boundary is weakened. The 0.13 mm Nb-microalloyed high silicon electrical steel strip has good magnetic properties at 800–1300 °C for 1 h. At 1200 °C, the grain growth and iron loss decrease due to the dissolution of the Nb-rich precipitates, so that the sample has a high comprehensive magnetic property: B8 is 1.31 T, B50 is 1.61 T, and P10/50 is 0.411 W/kg, P10/400 is 5.416 W/kg.

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 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 application of Fe–Si electrical steel as iron cores of transformers and engines requires it to be cold rolled into thin sheet because the deformation process is a path directly reaching a final dimension with good magnetic and mechanical properties. However, it is impossible for the Fe–6.5 wt%Si alloy to be directly cold rolled due to its embrittlement. One alternative way to improve its workability is warm rolling. In this work, warm deformation behavior of Fe–6.5 wt%Si alloy is studied. The results show that the flow stress decreases remarkably after 30% compression, accompanying with a reduction of micro-hardness, indicating a work softening behavior of the alloy. The size of the ordered domains and the degree of order decrease gradually with deformation, and a disordered alloy is obtained finally. When deformation reaches a certain value, small dislocation cells appear and finally subgrains are formed indicating the occurrence of dynamic recovery. It is concluded that the deformation-induced disordering and dynamic recovery are the main softening mechanisms.

Solid-state refrigeration technology based on elastocaloric effects (eCEs) is attracting more and more attention from scientists and engineers. The response speed of the elastocaloric materials, which relates to the sensitivity to the strain rate and measuring temperature, is a significant parameter to evaluate the development of the elastocaloric material in device applications. Because the Cu-Al-Mn shape memory alloy (SMA) possesses a good eCE and a wide temperature window, it has been reported to be the most promising elastocaloric cooling material. In the present paper, the temperature changes (ΔT) induced by reversible martensitic transformation in a columnar-grained Cu71Al17.5Mn11.5 SMA fabricated by directional solidification were directly measured over the strain rate range of 0.005–0.19 s−1 and the measuring temperature range of 291–420 K. The maximum adiabatic ΔT of 16.5 K and a lower strain-rate sensitivity compared to TiNi-based SMAs were observed. With increasing strain rate, the ΔT value and the corresponding coefficient of performance (COP) of the alloy first increased, then achieved saturation when the strain rate reached 0.05 s−1. When the measuring temperature rose, the ΔT value increased linearly while the COP decreased linearly. The results of our work provide theoretical reference for the design of elastocaloric cooling devices made of this alloy.

The microstructure evolution and stress-induced phase transformation (SIPT) characteristics of continuous columnar-grained (CCG) polycrystalline Cu–12 wt % Al alloy during the tensile deformation process were investigated to understand the ductility enhancement mechanism, which shows a tensile elongation of 28%, nine times as high as that of the conventional as-cast polycrystalline counterpart. The results show that the CCG alloy has highly-oriented 〈001〉β texture and straight low-energy grain boundaries (GBs) along solidification direction, which significantly promote grains compatibility during plastic deformation. Additionally, besides β 1 '→α 1 ' transformation, β 1 '→γ 1 '→α 1 ' SIPT was also observed simultaneously in the CCG polycrystalline Cu–12 wt % Al alloy, which is different from single crystalline and conventional polycrystalline counterparts. As a consequence of the special phase transformations, high phase transformation plasticity (15–20%) and prominent subsequent plastic deformation (8–13%) of the phase transformation product α 1 ' martensite can be obtained.

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.

With the goals of exploring the feasibility of replacing Zr with Fe and P in Cu–Cr–Zr alloys and developing Cu–Cr–Fe–P alloys with excellent mechanical and electrical properties, the effects of Fe and P additions on the microstructures and properties of the as-cast, cold-rolled and aged Cu-0.8Cr alloys are investigated. The results indicate that adding Fe and P into the Cu-0.8Cr alloy can promote the precipitation of a large amount of fine, uniformly dispersed Cr and Cr3P particles. From Cu-0.8Cr to Cu-0.8Cr-0.17Fe-0.048P, the area fraction of precipitates increases from 3.1% to 6.3% while their average diameter reduces from 1.6 μm to 1.4 μm. When subjected to 95% cold rolling plus 450 °C aging for 1 h, the Cu-0.8Cr-0.17Fe-0.048P alloy exhibits a Vickers hardness of 140.4 HV and an electrical conductivity of 73.2%IACS, higher than 96.7 HV and 58.4%IACS in the Cu-0.8Cr alloy. Among three different processing routes investigated, the one with initial 50% cold rolling → aging at 500 °C for 1 h → final 95% cold rolling allows the Cu-0.8Cr-0.17Fe-0.048P alloy to gain most in both its tensile strength (569 MPa) and electrical conductivity (64%IACS). The findings in this work provide insights to composition and processing designs for new Cu–Cr alloys with high strength and electrical conductivity.

With the goals of exploring the feasibility of improving the yield strength without decreasing the hot workability, four novel Co–30Ni-(7-x)Al–2W-1.5Mo–1Ta-(3.5 + y)Ti–12Cr-0.1Hf-0.08C-0.08B-0.4Si-0.01Zr (x = 0, 1, 1.5, 3, y = 0, 0, 0.7, 1.4 at%) γ′-strengthened wrought Co-base superalloys were designed, and the effects of Al and Ti on microstructure and properties of γ′-strengthened wrought Co-base superalloys were analyzed. Comparing the alloys 7Al-3.5Ti, 5.5Al-4.2Ti and 4Al-4.9Ti with the similar hot workability, the Al(at%)/Ti(at%) in the γ′ decreased with the decrease of Al(at%)/Ti(at%) in the alloys, this composition change in the γ′ made the alloys’ yield strength at room temperature and 800 °C increase from 915 MPa to 1025 MPa and from 764 MPa to 826 MPa, respectively. Based on the 6Al-3.5Ti alloy, the addition of 1 at% Al changed the γ′ compositions, which resulted in a decrease of yield strength at room temperature by 45 MPa but a significant increase of yield strength by 108 MPa at 800 °C, and this significant increase of yield strength at 800 °C may also be associated with the formation of numerous microtwins in 7Al-3.5Ti alloy; In the four experimental alloys, Mo preferentially partitions to the γ matrix, the relative content of Al and Ti has a negligible influence on the hot deformation resistance at 1150 °C, and there is no harmful phase after a heat treatment of 900 °C at 8 h + 750 °C at 12 h.

Abnormal grain growth induced by cyclic heat treatment for unidirectionally solidified Cu–Al–Mn shape memory alloys was investigated by electron backscatter diffraction. A Cu–17.5Al–11Mn (at%) alloy was initially fabricated by unidirectional solidification, showing [001] textures along the solidification direction with columnar grains and a high fraction of low-angle grain boundaries. Abnormal grain growth was then involved using cyclic heat treatment for the columnar polycrystal, during which the subgrains that formed because of precipitation served as a strong driving force. The migration of high-angle grain boundaries dominates the abnormal grain growth behavior, and no orientation deviation occurs during cyclic heat treatment so the large grains or single crystals maintain a [001] orientation. With repeated cyclic heat treatments, single-crystalline Cu–17.5Al–11Mn (at%) alloys showing [001] orientation with dimensions of 50 mm × 10 mm × 1 mm could be obtained, in which an excellent recoverable strain of more than 10% was observed.

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%.