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Cu Fe alloys with high iron content (Fe > 10 wt%) are a class of promising copper alloys with high strength and high conductivity. However, the strength and conductivity trade-off dilemma is a longstanding problem in the high iron content Cu Fe alloys owing to macro-segregation of iron particles and incomplete precipitation of solid solution iron atoms in the traditional casting process. We adopted a comprehensive strategy of designing the ultra-fine dual structures with fine copper grains and micro-nano iron particles, and adding phosphorus element to induce solid solution iron atoms precipitation to break through the above bottleneck. In this study, Cu 20Fe alloys with 0.05–1.0 wt% P were prepared through powder metallurgy process. The results showed that the addition of P promoted the precipitation of soluble Fe atoms, reduced oxygen content, and activated sintering. Ultimately, the strength and conductivity of cost-effective Cu 20Fe alloys were significantly improved. The annealed Cu 20Fe 0.1P alloys possess unprecedented comprehensive properties with 608 MPa tensile strength and 65.2% IACS electrical conductivity, which were 7.8% and 19.8% higher than the Cu 20Fe alloys, respectively. The annealed Cu 20Fe 1.0P alloys achieved 59.7% IACS electrical conductivity, increased by 10% compared to Cu 20Fe alloys. The results broke the conventional understanding that increasing P content deteriorated material properties. The influence of P on the microstructure and properties of powder metallurgy Cu 20Fe alloys was investigated in detail. These findings provide new insight into overcoming the dilemma of the inverted relationship between the strength and conductivity of copper alloys. • Simultaneous enhancement of the mechanical and electrical properties of Cu 20Fe alloys by introducing phosphorus. • The Cu 20Fe 0.1P alloys possess unprecedented comprehensive properties and property-costs. • The influence of P on the microstructure and properties of powder metallurgy Cu 20Fe alloys was investigated in detail. [ABSTRACT FROM AUTHOR]

In this work, copper ferroalloys (CFAs) with various Fe contents (5, 10 and 30 wt-%) were fabricated via the mechanical alloying and vacuum sintering method, followed by hot and cold rolling. Microstructure, mechanical, electrical and magnetic properties were investigated using scanning electron microscopy (SEM), X-Ray diffraction (XRD), tensile testing, four-point probe, vibration sample magnetometer and dc BH circuit tracer, respectively. The CFAs with homogenous and fine in-situ Fe particles prepared by powder metallurgy showed better performance compared with previously reported conventional casting. After annealing at 400°C, the cold-rolled CFA with 30 wt-% Fe had the tensile strength of 621 MPa, the electrical conductivity of 50.2% IACS, magnetic saturation strength (Ms) of 60.39 emu g−1 and coercivity (Hc) of 98.2 Oe, achieving a good combination of mechanical and functional properties. Relations between the microstructure and mechanical and functional properties are discussed in detail. [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]

Microstructure evolution and variations in mechanical properties of Al-Al2O3 nanocomposite produced by powder metallurgy were investigated and compared with commercially pure aluminum (Al-1050) after furnace annealing. Fine gas-atomized Al powder compacts were first sintered in flowing nitrogen, subsequently consolidated into wires by rotary swaging and eventually annealed at 300 and 500 °C for 24 h each. Scanning and transmission electron microscopy with energy-dispersive spectroscopy was utilized to document the microstructure evolution. Rotary swaging was proven to lead to a marked decrease in grain size. After heavy swaging to true deformation degree of φ = 6 and annealing at 500 °C, obvious recrystallization was observed at Al-1050’s existing grain boundaries and the crystals began to grow perpendicular to the flow direction. In the Al-Al2O3 nanocomposite, fabricated from d50 = 6 μm Al powder, recrystallization partially occurred, while grains were still extremely fine. Due to the dual role of fine-grained Al2O3 dispersion strengthening, the nanocomposite showed improved mechanical performance in terms of tensile strength, approximately twice higher than Al-1050 after annealing at 500 °C. [ABSTRACT FROM AUTHOR]

In this paper, Al-8.3Zn-2.3Mg-2.5Cu alloys with different oxygen contents were prepared through complex techniques including blending or ball milling, cold isostatic pressing, vacuum sintering, hot extrusion, and heat treatment, and their microstructure and mechanical properties were investigated. For the samples containing 0.15 wt% and 0.33 wt% oxygen, the sintered density values are 99.1% and 98.7% of the theoretical density, and the corresponding average grain sizes are 5.60 μm and 4.83 μm. After heat treatment, the average grain sizes of the samples with 0.15 wt% oxygen subjected to the extrusion ratios of 4:1, 9:1, and 17:1 are 5.17 μm, 4.28 μm and 3.83 μm, respectively, and the corresponding yield strengths are 607 MPa, 615 MPa, and 621 MPa. Moreover, the {111}<112> deformation texture changes to {001}<001> and {001}<111> recrystallization textures. In contrast, for the extruded sample (9:1 extrusion ratio) with 0.33 wt% oxygen, the grains are finer, and static recrystallization barely occurs with little variation in texture after heat treatment. This is due to the increase in content of thermostable γ-Al 2 O 3 particles. Accordingly, the sample with high oxygen content exhibits excellent comprehensive mechanical properties with the ultimate tensile strength of 719 MPa, yield strength of 690 MPa, and elongation of 11.5%. Regarding the strengthening mechanism, apart from the common precipitation strengthening, the contributions of dislocation strengthening and grain boundary strengthening are greater in the 0.33 wt% oxygen alloy than in the 0.15 wt% oxygen alloy. This is due to the pinning effect of γ-Al 2 O 3 particles on dislocations and grain boundaries. • The oxygen content of powder was increased by ball milling. • The effects of extrusion ratios on mechanical properties of Al–Zn–Mg–Cu alloys. • Static recrystallization was suppressed by thermostable γ–Al 2 O 3 particles. • Ultrahigh strength and toughness of Al–Zn–Mg–Cu alloy were obtained by fine grains, γ–Al 2 O 3 particles and precipitates. [ABSTRACT FROM AUTHOR]

Simultaneous improvement of both the strength and electrical conductivity of Cu–Fe alloys (CFAs) through the conventional casting method is an extremely challenging task. In this study, an attempt was made to overcome this issue via preparing CFAs with ultrafine alloy powders embedded with nano Fe particles. Ultrafine CFA powders with various Fe contents ranging from 5 to 50 wt.% were synthesized by a novel rapid solidification route, namely, gas–water combined atomization (GWA) process. The alloy powders prepared via GWA were then processed by pressureless sintering, hot rolling, annealing, and cold rolling. The microstructure evolution, mechanical properties, and electrical conductivity of CFAs were comprehensively investigated. The average size of Cu grain and Fe particles in all sintered CFAs was smaller than 3 and 2 μm, respectively. The grains of sintered CFAs were obviously refined by the Fe particles, and the addition of Fe inhibited the formation of Cu twins. After rolling, the Fe particles elongated and became fibrous along the rolling direction. The degree of formation of fibrous Fe enhanced with the increase of Fe content. Cold-rolled CFAs with 5–50 wt% Fe exhibited the tensile strength of 560–1250 MPa and conductivity of 33–65% IACS, indicating that CFAs in this study achieved superior mechanical and electrical properties. The microstructure evolution and strengthening mechanisms of CFAs were described. These findings can provide new insights into the powder metallurgy manufacturing of high-performance CFAs. • Ultrafine CFA powders were prepared by gas-water combined atomization. • The average size of Fe particles and grains of sintered CFAs was 2–3 μm. • Cold-rolled CFAs achieved superior mechanical and electrical properties. [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]

• 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]

FeCoNi concentrated solid-solution alloys (CSAs) and its modified version strengthened by in-situ formed nano-sized particles are successfully manufactured through mechanical alloying and spark plasma sintering method. Both the as-milled powders and the bulk materials are of single face-centered cubic structure. After sintering and heat treatment, grains are refined by 68% with the addition of oxides. In oxide dispersion strengthened (ODS) FeCoNi CSAs, the majority of nano-sized particles with diameter ranging from a few to ~ 40 nm are uniformly distributed in the matrix, and most of them are identified as Y 2 Ti 2 O 7. Electron backscattered diffraction results reveal that the recrystallization process is suppressed due to the existence of the nano-sized particles. The size and distribution of oxide particles in the matrix can be controlled by adjusting experiment parameters of the mechanical alloying process and annealing treatment. Refined grains and high-density nano-sized particles result in enhanced compressive yield strength for ODS-FeCoNi CSAs at room temperature and 700 °C, which is 1295 MPa and 127 MPa, respectively. Image 1 • Nano-sized oxide particles were introduced into FeCoNi based ternary alloys by mechanical alloying. • Nano-sized particles with diameter ranging from a few to ~40 nm are evenly distributed in matrix and identified as Y 2 Ti 2 O 7. • Both the as-milled powders and the bulk materials are of single face-centered cubic structure. • High compressive yield strength is obtained at RT and 700 °C for ODS-FeCoNi CSAs, which is 1295 and 127 MPa, respectively. [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]

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]