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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]

Al matrix composite reinforced by hexagonal boron nitride (h-BN) with nearly full densification was successfully fabricated by the semi-solid powder metallurgy technique. The h-BN/Al composites were synthesized with elemental pure Al powder size of d 50 =35, 12 and 2 μm. The powder morphology and the structural characteristics of the composites were analyzed using X-ray diffraction, scanning and transmission electron microscopy. The density, Brinell hardness and compressive behavior of the samples were characterized. Density measurement of the Al composites revealed that the composite densification can be effectively promoted by plenty of embedded liquid phase under pressure. Composites prepared using Al powder with varying granularity showed different grain characteristics, and in situ recrystallization occurred inside the original grains with 35 μm Al powder. A sharp interface consisting of Al/Al 2 O 3 /h-BN was present in the composites. Both the compressive strength and the fracture strain of the investigated composites increased with the decrease of the Al powder size, along with the Brinell hardness. The composite with 2 μm Al powder exhibited the highest relative density (99.3%), Brinell harness (HB 128), compressive strength (763 MPa) and fracture strain (0.299). [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]

In this study, a novel dispersion-strengthened copper-tungsten alloy with improved mechanical properties, electrical conductivity, and thermal stability was prepared by mechanical alloying. Cu-WO 3 powder blend was milled to obtain a uniform dispersion of WO 3 in copper and the WO 3 particles were subsequently reduced to tungsten to obtain the Cu–W composite. The tungsten nanoparticles dispersed in the copper matrix have an average size of 32 nm, without agglomeration, and are highly stable. The cold-rolled Cu-5 vol% W reached a tensile strength of 596 MPa, elongation of 7.7%, and electrical conductivity of 84% IACS (International annealing copper standard). In particular, the cold-rolled alloy retains the tensile strength of over 400 MPa and reasonable ductility even after annealing at 800 °C. The remarkable improvement in mechanical properties and thermal stability are attributed to the pinning effect of highly dispersed nano-sized W particles in the Cu matrix. [ABSTRACT FROM AUTHOR]

A superior comprehensive property of Cu–Ni–Si–Al 2 O 3 alloy, including microhardness of 184.4 HV, yield strength of 573 MPa, tensile strength of 607 MPa, and excellent electrical conductivity of 54.9 %IACS, is obtained with the minute addition of alloying elements (∼0.75 wt% Ni and ∼0.20 wt% Si) and nanometer scaled Al 2 O 3 particles. The influence of these Al 2 O 3 particles on the precipitation process and strengthening behaviors has been investigated by the scanning electron microscopy (SEM) equipped with electron-backscattered diffraction (EBSD) and transmission electron microscope (TEM). The results show that the addition of nanometer scaled Al 2 O 3 particles can cause the increase of dislocation density and refinement of the grains during cold deformation and the following aging process. The precipitation kinetics are consequently promoted due to heterogeneous nucleation around the dislocations, sub-grain and grain boundaries and the Al 2 O 3 particles, resulting in the improvement in distribution and refinement of precipitation. The volume fraction and number density of the precipitates are increased, resulting in the simultaneous enhancement of mechanical and electrical properties in the Cu–Ni–Si–Al 2 O 3 alloy. This study provides a significant guidance for the design of precipitation hardening copper alloy, by introducing the precipitation strengthening and dispersion strengthening. [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]