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In this paper, the microstructural evolution, precipitation behavior and mechanical properties of 2195 Al-Li alloys prepared by powder metallurgy (PM) combined with hot extrusion were investigated systematically. The results show that the deformation of PM 2195 Al-Li alloys during hot extrusion is dominated by the coupling of dynamic recovery with continuous dynamic recrystallization. The homogeneously distributed needle-like T 1 phase is precipitated in the matrix after T6 treatment. The T6-treated sample exhibits a perfect combination of strength and ductility, that is, ultimate tensile strength of 662 MPa, yield strength of 617 MPa and uniform elongation of 6.6 %. The strengthening of heat-treated alloys originates from densification, work hardening, grain refinement and precipitation strengthening. It is noted that the precipitation strengthening of T 1 phase is the dominant mechanism. Therefore, this work should suggest a strategy for developing novel Al-Li alloys with excellent mechanical properties. • The 2195 Al-Li alloys were successfully prepared by powder metallurgy and hot extrusion. • The tensile strength, yield strength and elongation of the 2195 Al-Li alloy were 662 MPa, 617 MPa and 6.6 %, respectively. • Mechanical properties of the alloy were enhanced by densification, work hardening, grain refinement and precipitation. • The precipitation strengthening of T 1 phase is the dominant mechanism. [ABSTRACT FROM AUTHOR]

Powder metallurgy Cu-30Fe alloy was prepared by mechanical alloying, pressureless sintering, and rolling processes. The alloy microstructure and physical properties affected by rolling were studied. The Fe particles were small and uniformly distributed in the Cu matrix. The average Fe particle size in the sintered state was 1 µm, and particles had subspherical or irregular shapes. The Fe particles became elongated, tadpole-shaped, and spindle-shaped as a result of rolling. At the same time, the Cu grains were elongated and refined, while the Cu grains near the Fe particles were finer as a result of the coordinated deformation of the soft Cu and hard Fe phases. After annealing at 400 °C, the cold-rolled Cu-30Fe alloy had 620 MPa tensile strength, 10% elongation, and 50% IACS electrical conductivity, achieving a good combination of mechanical and functional properties. The coordinated deformation behavior and grain refinement mechanisms of both Cu and Fe phases due to rolling were described, along with the microstructure and physical properties evolution. • Cu-30Fe alloys with Fe particles were fabricated by powder metallurgy and rolling. • Grain refinement mechanisms of Cu and Fe phases due to rolling were described. • Microstructure and physical properties of Cu-30Fe alloys were studied. • Cu-30Fe has 620 MPa tensile strength, 10% elongation, 50%IACS electrical conductivity. [ABSTRACT FROM AUTHOR]

Amorphous soft magnetic composites have been attracting attention because of its low core loss under high frequency application. It is demanded that the powder for fabricating amorphous soft magnetic composites has amorphous structure and nearly spherical shape, which facilitates the uniform coating of insulator on the surface of powder particles. In this paper, amorphous Fe 73.5 Si 13 B 11 Cr 1 C 1.5 (at%) powder was produced by gas-water combined atomization process which takes advantages of both gas atomization and water atomization, and its properties was compared with powder produced by gas atomization and water atomization. Gas-water combined atomization powder with particle size of −60 μm were found to be amorphous with low coercivity, and the shape of particles was nearly spherical. The permeability of magnetic powder cores prepared with three kinds of powder first increased and then decreased with annealing temperature, and the core loss first decreased and then increased. The cores prepared with gas-water combined atomization powder showed the best overall properties, with an effective permeability of 26.9, a relative permeability of 83.3% under a superimposed DC magnetic field of 7.96 kA/m, a core loss of 258 mW/cm3 under a frequency of 100 kHz, and a magnetization intensity B m of 0.05 T after annealing at 793 K in nitrogen gas. • Fe 73.5 Si 13 B 11 Cr 1 C 1.5 soft magnetic powder with amorphous microstructure is produced by gas-water combined atomization. • The cooling rate of gas-water combined atomization is close to water atomization, but higher than gas atomization. • The magnetic powder cores made of gas-water combined atomized powder have the high DC BIAS characteristics and low loss. [ABSTRACT FROM AUTHOR]

After high-temperature forging and rapidly cooling, the microstructure evolution and spheroidization mechanism of powder metallurgy Ti-6Al-4 V alloy have been clarified. The spheroidization process is divided into two asynchronous stages. The initial stage is primarily characterized by the initial shearing and twisting of GBα grain boundaries, as well as the deformation of lamellar structure. Subsequently, the fragmentation of original GBα grain boundaries and the fracture of intra-granular α lamellae are observed. This process is accompanied by grain twisting and substructure formation, especially the division of lamellae through interface splitting and the segregation of local chemical elements. The differential accumulation of elements around the fractured and twisted grains suggests that element segregation and interfacial energy play a significant role in microstructure evolution. Therefore, the static spheroidization process largely depends on the formation and evolution of dislocation substructures, and the reduction of interfacial energy may be a key factor driving this process. These findings provide a theoretical basis for manufacturing metals with specific anisotropic properties by controlling microstructure evolution. [Display omitted] • Dynamic recrystallization drives microstructural changes in Ti64 alloy forging. • GBα and internal spheroidization are related to crystal rotation asynchronously. • Elemental segregation affects the occurrence of grain boundary spheroidization. • Increased activity of pyramidal slip systems reveals anisotropy in hcp metals. [ABSTRACT FROM AUTHOR]

High-plasticity in-situ TiB/Ti matrix composites (TMCs) are fabricated by in-situ reaction between Ti and ZrB 2 powder during vacuum sintering followed by hot rolling. Uniform microstructure is observed in the TMCs with obvious grain refinement. Compared with pure titanium, the mean grain size of Ti-2.0 wt% ZrB 2 composite significantly decreases from 50.7 µm to 17.5 µm, decreasing by 65%. Accordingly, Ti-2.0 ZrB 2 composite displays outstanding mechanical properties of 734.6 MPa in ultimate tensile strength, 579.0 MPa in yield strength, 21.4% in elongation, while these values of pure Ti are 632.4 MPa, 507.0 MPa, and 14.2%, respectively. The strength improvement of TMCs can be mainly attributed to five parts: grain refinement, solid solution strengthening, load transfer mechanism, CTE mismatch between TiB and Ti matrix and the dislocation substructure hardening. Among them, dislocation substructure hardening (more than 50% of the total improvement) takes the dominant position in strength increment in the as-rolled TiB/Ti matrix composites. [Display omitted] • In-situ TiB/Ti composites were synthesized by ZrB 2 additive via PM process. • Obvious grain refinement is found with grain size decreasing from 51 µm to 16 µm. • TiB/Ti composites show a balanced combination of good strength and high ductility. • Ti-2 wt% ZrB 2 sample has UTS of 734 MPa, YS of 579 MPa and EL. of 21%. • Strength increment caused by dislocation substructure hardening is ranged from 47.2 MPa to 116.6 MPa. [ABSTRACT FROM AUTHOR]

• High-plasticity PM Ti material with high O content is prepared with ZrO 2 addition. • The strength-ductility trade-off dilemma of PM titanium alloy is broken. • Ti-1.0 wt% ZrO 2 sample (0.56 wt% O) has UTS of 824 MPa and EL. of 15%. • Zr and O atoms fully dissolve in the Ti matrix, leading to lattice constant change. • The strengthen effect of ZrO 2 is calculated as 146.7 MPa/wt% ZrO 2. [Display omitted] High-plasticity titanium materials with high oxygen content were prepared by powder metallurgy (PM) and hot rolling, using pure Ti and ZrO 2 powder as raw materials. Completely dissolved oxygen and zirconium atoms resulted in the lattice constant change, thereby increasing the strength. Although the oxygen content was up to 0.56 wt% (much higher than the oxygen threshold of 0.33 wt%), PM Ti still exhibited high plasticity. The Ti-0.5 wt% ZrO 2 sample (0.43 wt% O) had UTS of 737 MPa and EL. of 28%, while the Ti-1.0 wt% ZrO 2 sample (0.56 wt% O) had UTS of 824 MPa and EL. of 15%. Compared to pure Ti, the addition of 0.5 wt% ZrO 2 resulted in a noticeable increase in UTS (increased by 9%) and EL. (increased by 19%). The strength-ductility trade-off dilemma of PM Ti alloy was broken. The formation of fine and equiaxed dynamic recrystallized grains may be one of the reasons that increased the ductility. The reinforcement effect of ZrO 2 was calculated as 146.7 MPa/wt% ZrO 2. [ABSTRACT FROM AUTHOR]

• ELI Ti-6Al-4V alloys with 0.07 wt% O are produced by sintering HDH powder. • O content of powder exposed to the air is proportional to its specific surface area. • Fine near-equiaxed α of 20 µm is obtained by vacuum sintering and capsule-free HIP. Ti alloys produced from HDH powder have suffered from high O/N interstitials content. In the present study, a whole well-protected process from Ti sponge to as-sintered materials is adopted, and thus the lowest O/N contents of as-sintered materials are 0.07 wt% and 0.018 wt%, within the specification of Grade F-23 (Ti-6Al-4V ELI) according to ASTM B988-13. The passivation law of powder and its compact has also been studied in detail. Subsequently, sintering experiment indicates fine ELI powder has an excellent sinterability. A relative density over 96% can be obtained by sintering at 1100 °C. Capsule-free HIP post-sintering is performed to achieve full density and obtain fine and near-equiaxed α grain at the same time. The as-HIPped sample has better comprehensive mechanical properties, with strength exceeding 970 MPa and elongation exceeding 16.4%. [ABSTRACT FROM AUTHOR]

Powder metallurgy in-situ TiB/Ti6Al4V composites with good mechanical properties are fabricated by vacuum sintering using high-oxygen HDH Ti6Al4V and CaB 6 powders. CaB 6 can not only be used as a boron source, but also synthesize Ca-Ti-O ternary compounds with solid solution oxygen in titanium matrix. Therefore, it has a purification effect on oxygen scavenging, and the relative density of TiB/Ti6Al4V composites can exceed 99%. The interface between titanium matrix and TiB is semi-coherent. Good interfacial adhesion, high density, and reduced oxygen content make the composite material exhibit higher ductility. Although the equivalent oxygen content for Ti6Al4V-0.1CaB 6 composite material is about 0.57 wt%, the elongation still reaches 9.5%, which is 57.4% higher than that of CaB 6 -free sample. Besides, the ultimate tensile strength reaches 1015.6 MPa, and the yield strength is 932.0 MPa. [Display omitted] • In-situ TiB strengthened Ti64 material is prepared via adding CaB 6 in HDH powders. • CaB 6 reacts with solid dissolved oxygen in Ti matrix to form ternary oxides. • The formation of TiB can significantly refine the matrix structure. • CaB 6 acts as an effective oxygen scavenger to reduce oxygen content in matrix. • Ti64-0.1CaB 6 has good ductility of 9.5% although its [O] e content is 0.57 wt%. [ABSTRACT FROM AUTHOR]

TiAl-based alloy is an excellent high-temperature structural material, but poor hot workability has been the bottleneck hindering its development. In this study, we take into account the hot workability and mechanical properties of Ti-48Al alloy through microstructure adjustment. Powder metallurgy Ti-48Al alloy prepared by vacuum sintering is used as the raw material, which has a near-γ microstructure composed of equiaxed grains. Although the composition is simple, the alloy achieves high mechanical properties after forging with 75 % deformation. Controlling the forging temperature to 1300 °C can make the microstructure transform into a duplex structure composed of γ/α2 lamellar colonies and γ equiaxed grains. As-forged alloy has an ultimate tensile strength of 650 ± 17 MPa and a yield strength of 644 ± 16 MPa at room temperature. It still maintains high strength at high temperature, with ultimate tensile strength of 684 ± 19 MPa at 500 °C, 700 ± 19 MPa at 700 °C, and 320 ± 10 MPa at 900 °C. In addition, the alloy has good ductility with elongation of 58.2% due to dynamic recrystallization at 900 °C. • Mechanical property is significantly improved by forging with simple composition. • The alloy has ultrafine equiaxed grain of 2.45 µm and lamellar spacing of 20–50 nm. • Duplex microstructure without remnant lamellae forms in PM Ti-48Al alloy. • Ti-48Al alloy exhibits great plasticity of 58.2 % at 900 °C. [ABSTRACT FROM AUTHOR]

The hot deformation behavior and microstructural evolution of powder metallurgy (PM) Ti-6Al-4V are investigated using the Arrhenius constitutive model, hot processing map, microstructure observation, and hot deformation mechanism analysis. The optimal processing parameters obtained from the hot processing map are 1323–1423 K at 0.1–1 s−1, and 1423–1523 K at 1–10 s−1. Hot deformation in β region is attractive for PM Ti-6Al-4V. The dominant hot deformation mechanism of PM Ti-6Al-4V is dynamic recrystallization (DRX) in the (α + β) and β regions. Continuous dynamic recrystallization (CDRX) is the dominant mechanism in the (α + β) region. The combination of CDRX and discontinuous dynamic recrystallization (DDRX) is the preferred mechanism in the β region. The power-dissipation efficiency is affected by DRX, which consumes dislocations and refines the microstructure. Specific hot working parameters for thermomechanical processing (TMP) of PM Ti-6Al-4V are identified. [Display omitted] • Proper hot working parameters for the thermomechanical processing are identified. • Hot deformation of PM Ti-6Al-4V was more effective in the β region than in the (α + β) region. • Undesired microstructure and hot working parameters have been addressed. • The dominant hot deformation mechanism is dynamic recrystallization. [ABSTRACT FROM AUTHOR]

Poor sinterability of powder metallurgy TiAl-based alloy is an important factor that restricts its industrial production. In this paper, we improve the sinterability of Ti-48Al alloy by adding Co element. In such case, the relative density of Ti–48Al based alloy sintered at 1250 ℃ increases from 82.6% to 96% with an increase of Co content from 0 to 1.5 at%. The densification improvement is caused by liquid TiAl 2 Co phase, which is formed at 1230 ℃. Then, uniform and fine near-γ microstructure is obtained, and the grain size increases with the increasing of Co content. More than 70% of grains in the Ti-48Al-0.5Co alloy are smaller than 2 µm. Overall, Ti-48Al-0.5Co alloy has better comprehensive performance, with compressive strength of 2533 MPa, yield strength of 683 MPa and fracture strain of 29.5%. [Display omitted] • High-density Ti-48Al alloy with Co addition is prepared using irregular powder. • Liquid TiAl 2 Co phase is formed to promote densification sintering. • Sintering temperature of Co-added TiAl alloy is reduced by 50 ℃. • More than 70% of grains in the Ti-48Al-0.5Co alloy are smaller than 2 µm. • Ti-48Al-0.5Co has superior compressive and yield strengths of 2533 MPa and 683 MPa. [ABSTRACT FROM AUTHOR]

Microstructure and mechanical properties of two kinds of oxide dispersion strengthened concentrated solid solution alloys (CSAs), FeCoNi-1.5Y 2 O 3 (FCNY) and FeCoNi-1.2Ti-1.5Y 2 O 3 (FCNTY), are studied through a comparing investigation with FeCoNi (FCN) CSAs. All these alloys are fabricated by mechanical alloying, spark plasma sintering, hot rolling and annealing treatment. For three kinds of alloys, both the as-milled powders and bulk materials are of single face-centered cubic structure. Electron backscattered diffraction results reveal that the texture transformation is suppressed during the hot rolling process because the movement of grain boundaries is hindered by the oxide particles. Compared with FCN CSAs, grains are refined by 43% and 47% for FCNY and FCNTY CSAs, respectively. Nano-sized Y 2 O 3 (monoclinic structure) and Y 2 Ti 2 O 7 (pyrochlore structure) particles are uniformly distributed in FCNY and FCNTY CSAs, respectively. Both Y 2 O 3 and Y 2 Ti 2 O 7 particles show a semi-coherent relationship with the matrix. Yield strength of FCN, FCNY and FCNTY CSAs is 559, 981 and 1050 MPa, respectively. Theoretical calculations illustrate that high strength of FCNY and FCNTY CSAs comes from refined grains and high-density nano-sized oxide particles. • Nano-sized Y 2 O 3 and Y 2 Ti 2 O 7 particles were introduced into FeCoNi based concentrated solid solution alloys (CSAs). • Average size, crystal structure and orientation relationship of Y 2 O 3 and Y 2 Ti 2 O 7 particles were analyzed. • Hot rolling may promote the "cubic → monoclinic" phase transition of Y 2 O 3 particles in FeCoNi-1.5Y 2 O 3 CSAs. • Enhanced strength in ODS-FeCoNi CSAs originates from the refined grains and high-density nano-sized oxide particles. [ABSTRACT FROM AUTHOR]