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Ti-6554 (Ti-6Cr-5Mo-5V-4Al) alloy has attractive potential as a new structural material in the aviation field due to its excellent mechanical properties. However, it is expensive to manufacture, which can limit its application. Powder metallurgy (PM) is an economic technology to reduce the cost of titanium alloys. In this study, PM Ti-6554 alloy was prepared using irregular powder via vacuum sintering followed by forging. The influence of cooling rate (air cooling and water quenching) of as-forged sample on its microstructure was studied by scanning electron microscopy, electron backscatter diffraction and other analytical means. Experimental results showed that different cooling rates determined the structures of α and β phases. Compared with air-cooled sample, the water-quenched sample only had β phase microstructure without α phase precipitates. As-forged PM Ti-6554 alloy subjected to water quenching achieved ultimate tensile strength of 942 MPa and elongation of 20% and also had fine β grains of 10 μm. After solution treatment and aging, the sample exhibited high ultimate tensile strength (1211 MPa) and elongation (13.8%). Overall, PM Ti-6554 alloy possessed a good combination of high strength and reasonable ductility. This work marks a vital step forward in the application of high-performance PM Ti-6554 alloys. [ABSTRACT FROM AUTHOR]

Powder metallurgy (PM) offers cost-effective potential for manufacturing titanium and titanium alloys. High oxygen content on titanium powder surface is a key problem affecting the mechanical properties of PM Ti alloys. Therefore, this study proposes a chloro-deoxidation method to reduce the oxygen content of titanium powder via introducing stannous chloride (SnCl2) into titanium powder. In the sintering process, SnCl2 reacts with the surface oxide on titanium powder to remove the oxide film, and thus forms gas TiClxOy escaping from Ti matrix, resulting in the decrease of oxygen content. With ~ 2.5 wt.% SnCl2 addition, the oxygen content reduces from 0.6 wt.% to 0.5 wt.%. Accordingly, the elongation of as-sintered Ti-SnCl2 sample significantly increases from 4.8% to 11% (increasing by 129%), while the tensile strength decreases from 815 MPa to 788 MPa. After HIP treatment, the elongation increases from 11% to 13%, and the strength is about 765 MPa. Although same Sn content (5 wt.%) is added in Ti samples, Ti-SnCl2 sample shows higher elongation value of 9.4% compared to Ti-Sn sample (3.6%), due to lower oxygen content. [ABSTRACT FROM AUTHOR]

The effects of solution-aging treatment on microstructure and mechanical properties of powder metallurgy (PM) Ti-6554 titanium alloy were investigated. PM Ti-6554 titanium alloy can achieve a good balance between strength and ductility after solution treatment at 810°C/30 min with furnace cooling and aging treatment at 520°C/6 h. Accordingly, the ultimate tensile strength, yield strength and elongation were 1360 MPa, 1323 MPa and 9.0%, respectively. The alloy had smaller α phase grain size (~ 0.69 μm), and its volume fraction was 73%. When the solution temperature increased from 810°C to 850°C, the ultimate tensile strength increased to 1601 MPa, the yield strength increased to 1543 MPa, and the elongation reduced to 3.5%. Microstructure results showed that the grain size of α phase gradually increased, while the volume fraction of α phase showed the opposite trend. When the solution temperature remained constant, slower cooling rate was beneficial to increase the alloy strength and maintain the strength-plasticity matching. [ABSTRACT FROM AUTHOR]

In this study, phosphorus-containing Fe-5 wt.% Si silicon steel sheet was prepared by powder loose sintering followed by hot rolling. Defect-free sheet with high P content was achieved. The study found that P effects on sintering promotion and processing deterioration were significantly suppressed by the presence of Si in steel. Appropriate P content would significantly improve the mechanical and magnetic properties of the sample. Under a comprehensive consideration, P content of 0.3-0.5 wt.% was suitable for silicon steel. Compared with P-free silicon steel, with 0.3 wt.% P addition, the tensile strength of silicon steel increased from 521 MPa to 680 MPa. As to the magnetic performance, the sample with 0.5 wt.% P had B8 of 1370.5 mT, and W10/50 0f 1.16 W·kg−1, while those for P-free sample were 1332.3 mT, and 1.46 W·kg−1, respectively. FeP phase with special morphology would be precipitated in samples with P addition. [ABSTRACT FROM AUTHOR]

In this study, a novel W and TiO2 synergistic strengthened copper matrix nanocomposite was prepared by a powder metallurgy route with a mechano-chemical method and subsequent consolidation. Nano-sized W and TiO2 particles in the composite powder were fabricated by solid-phase reaction during the mechanical alloying procedure. The average sizes of W and TiO2 particles were only 51 and 171 nm, far finer than single-phase particle-strengthened composites. It was found that the nanoparticles effectively resisted the grain coarsening in the copper matrix, containing the grains with an average size of 350 nm. The ultimate tensile strength and electrical conductivity of the copper composite are 520 MPa and 74 IACS%, achieve an ideal trade-off between them. The observations suggested that the nanoparticles were highly uniformly dispersed in the copper matrix, and the particle coarsening was restrained as the results of the interaction effects between W and TiO2 nanoparticles. [ABSTRACT FROM AUTHOR]

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]

The high thermal stability of pure Al conductors is an urgent requirement for their applications in power transmission lines. Powder metallurgy (PM) Al conductor was produced in this work from Al powder with a low oxygen content (~0.1 wt%), followed by cold isostatic pressing, sintering, hot extrusion, and cold drawing. The microstructure evolution, mechanical properties and electrical conductivity of hot-extruded rods and cold-drawn wires before and after annealing at 300 °C and 500 °C were investigated. The γ-Al 2 O 3 nanoparticles located primarily at high angle grain boundaries promote the stabilization of Al grains, resulting in enhanced annealing strength (89 MPa), almost twice higher than commercial pure Al (45 MPa). Fine grains and texture play a significant role in the overall strength (160 MPa) of PM Al conductors. One interesting finding is that the electrical conductivity of cold-drawn wires (60.2% IACS) is higher than the hot-extruded rods (58.7% IACS) due to the beneficial evolution of initial Al 2 O 3 film and grain boundaries. The compatibility of documented strength-structure Hall-Petch relation was discussed. Optimal properties (172 MPa ultimate tensile strength and 60.2% IACS electrical conductivity) were obtained through cold drawing. These results push forward the potential application of PM Al in heat resistant conductors. [ABSTRACT FROM AUTHOR]

Oxygen and carbon impurity residues and low density are the main issues for Ti gelcasting. To overcome these difficulties, this study develops a low-oxygen isoprene (Ip)/polyvinyl butyral (PVB) gel system to achieve Ti gelcasting using hydride-dihydride (HDH) Ti6Al4V powder. Slurries with 48 vol% solid loading content are employed to achieve moulding followed by cold isostatic pressing. During gelcasting, powder particles are held in place by the cross-linking of Ip monomer with PVB as adhesive to maintain shape. After sintering, nearly fully dense (4.38 g/cm3) Ti6Al4V alloys with low interstitial contamination (O: 0.356 wt%, C: 0.14 wt%) are successfully fabricated. The samples exhibit acceptable mechanical performance, with ultimate tensile strength of 1062 MPa, yield strength of 987 MPa, and elongation of 8.75%. Typical plastic fracture with river patterns is observed, which is distinctly different from that of HEMA based sample. [Display omitted] • Gelcasting Ti6Al4V parts with density of 4.38 g/cm3 are prepared using HDH powders. • A potential gelcasting method is proposed based on Ip/PVB system combined with CIP. • The tensile strength and elongation are 1062 MPa and 8.75%, respectively. • Oxygen content is significantly reduced from 0.88 wt% to 0.36 wt%. • Carbon content decreases from 0.26 wt% to 0.14%, decreasing by 46%. [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]

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]

Abstract High-quality Ti 2 AlNb alloys were prepared from blended elemental powders via cold isostatic pressing and pressureless vacuum sintering. When sintered at 1200 °C, the Ti-23Al-17Nb alloy attained a very high relative density (98.7%) and low contents of interstitials (0.1 wt% O, 0.03 wt% N and 0.005 wt% H). Three crystalline phases – B2, α 2 , and orthorhombic (O) – were observed in a fine and homogeneous microstructure in the sintered samples. The fine microstructure and low interstitials account for the good mechanical properties achieved: approximately 941 MPa of ultimate tensile strength, 862 MPa of yield strength and 11.7% of elongation. Highlights • Ti-23Al-17Nb with high relative density (98.7%) was prepared by vacuum sintering from blend elemental powder. • The as-sintered Ti-23Al-17Nb has low interstitials, about 0.1 wt% of O, 0.03 wt% of N and 0.005 wt% of H. • The mechanical properties of as-sintered Ti-23Al-17Nb is about 941 MPa in UTS, 862 MPa in YS and 11.7% in elongation. [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 short communication presents a synergistical reinforced Ti–48Al alloy with multiple Ti–Al intermetallic compounds which was prepared with irregular pre-alloyed powders by vacuum sintering at low temperature (1250°C). With simple composition, this alloy has tensile and yield strength of 593 ± 8 MPa and 435 ± 5 MPa at room temperature, and more than 510 MPa and 490 MPa at 700°C, reached the level of Ti–Al alloys with complex composition. • Ti–48Al alloy is synergistically reinforced by multiple intermetallic compounds. • Nano-sized and submicron-sized intermediate phases form and refine grain growth. • Low sintering temperature avoids the decomposition of formed intermetallic phases. • Mechanical properties significantly improve while alloy composition is simplified. [ABSTRACT FROM AUTHOR]