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Fine-grained tungsten heavy alloys (WHAs) with a non-equiatomic Ni 5.5 Fe 2.5 CoCr high entropy alloy (HEA) as binder were successfully fabricated through spark plasma sintering (SPS). The influence of binder content and composition on the microstructure and mechanical properties of WHAs were systematically investigated. The average W grain size and W–W contiguity decreased with increasing Ni 5.5 Fe 2.5 CoCr content. The Ni 5.5 Fe 2.5 CoCr binder inhibited the growth of tungsten grains, resulting in finer tungsten grains (3.5 ± 1.5 μm) in the 90W–Ni 5.5 Fe 2.5 CoCr alloy than in the conventional 90W–7Ni–3Fe alloy. This alloy showed an excellent tensile strength of 1392 ± 33 MPa. The high strength is achieved through the synergistic effect of fine-grain strengthening, twinning strengthening, dispersion strengthening and solid-solution strengthening. In contrast, WHAs using equiatomic NiFeCoCr as binder showed lower tensile strength (540 ± 26 MPa), caused by the formation of brittle μ phase in the binder phase. This work provides a pathway for utilizing the non-equiatomic HEA as a binder in the development of high-strength WHAs, thereby expanding their application prospects. • Fine-grained tungsten heavy alloys (WHAs) using a novel non-equiatomic Ni 5.5 Fe 2.5 CoCr high-entropy binder were synthesized. • The formation of Cr 2 O 3 phases were found in binder phase after sintering. • Twin structures were formed in γ-(Ni, Fe, Co, Cr, W) binder phase. • W–Ni 5.5 Fe 2.5 CoCr alloy has fine W grains and high strength. • Mechanisms of the high strength of 90W–Ni 5.5 Fe 2.5 CoCr alloy are elucidated. [ABSTRACT FROM AUTHOR]

In this work, high volume fraction Y 2 O 3 dispersion strengthened Ti-free and Ti-doped Cu samples were prepared by mechanical alloying, high temperature heat treatment and powder compact extrusion to study the role of alloying Ti element on microstructures, mechanical properties and electrical conductivity of the extruded samples. It is found that the addition of a small amount of 0.4 wt.%Ti effectively suppresses the coarsening of Y 2 O 3 particles during material fabrication, which produces smaller and more uniform oxide particles distributed in a homogeneous ultrafine grained Cu matrix. However, a heterogeneous Cu matrix microstructure, consisting of elongated micrometer-scale Cu grains and equiaxed ultrafine Cu grains, is observed in the Ti-free sample due to significant coarsening of the Y 2 O 3 particles. The different microstructural features of the two extruded samples lead to distinctively different mechanical behaviors and electrical conductivities. The energy dispersive X-ray spectrometry elemental and high resolution transmission electron microscopy analysis suggest that the stabilizing mechanisms of the Y 2 O 3 particles involve both the segregation of Ti atoms to the surface layers of large Y 2 O 3 particles and dissolution of Ti atoms into small Y 2 O 3 particles to form complex particles. [ABSTRACT FROM AUTHOR]

Introducing coarse grains into nanocrystalline (NC) and ultrafine grained (UFG) metallic materials can lead to an excellent combination of strength and ductility. In this study, we produced Al 2 O 3 dispersion-strengthened (Al 2 O 3 -DS) Cu with heterogeneous microstructure by mechanical alloying (MA) of Cu-Al 2 O 3 powder mixture followed by spark plasma sintering (SPS) and hot extrusion (HE). For direct comparison, one sample was prepared by hot extrusion only without prior SPS of mechanically alloyed (MAed) powders. The microstructure of materials produced via a combination of SPS and HE possessed the heterogeneous microstructure consisting of Al 2 O 3 -free coarse grained (CG) Cu bands and Al 2 O 3 -rich UFG Cu regions. These different microstructural regions were found to play different roles on the tensile and electrical properties and their presence can be tuned to achieve desired mechanical and electrical properties. We also discuss the possible mechanisms responsible for the formation of the heterogeneous microstructure in the samples produced by a combined process of SPS and HE. [ABSTRACT FROM AUTHOR]

Combined with microstructure characterization and properties tests, the effects of Zn contents on the mechanical properties, corrosion behaviors, and microstructural evolution of extruded Al–Li–Cu–Mg–Ag alloys were investigated. The results show that the increase in Zn contents can accelerate hardening kinetics and improve the hardness of peak-aged alloys. The Zn-added alloys present non-recrystallization characteristics combined with partially small recrystallized grains along the grain boundaries, while the T1 phase with finer dimension and higher number density could explain the constantly increasing tensile strength. In addition, increasing Zn contents led to a lower corrosion current density and a shallower maximum intergranular corrosion depth, thus improving the corrosion resistance of the alloys. Zn addition, distributed in the central layer of T1 phases, not only facilitates the precipitation of more T1 phases but also reduces the corrosion potential difference between the T1 phase and the matrix. Therefore, adding 0.57 wt.% Zn to the alloy has an excellent combination of tensile strength and corrosion resistance. The properties induced by Zn under the T8 temper (solid solution treatment + water quenching + 5% pre-strain+ isothermal aging), however, are not as apparent as the T6 temper (solid solution treatment + water quenching + isothermal aging). [ABSTRACT FROM AUTHOR]

In this paper, the influence of extrusion ratio and secondary processing of hot rolling on microstructural features and tensile mechanical properties of samples produced by extrusion of mechanically alloyed Cu-5vol.%Al 2 O 3 alloy powders is investigated. The results show that the extrusion ratio and subsequent rolling greatly affect the sizes of Cu grains and Al 2 O 3 particles, spatial distribution of Al 2 O 3 particles and dislocation density in the prepared bulk Cu-5vol.%Al 2 O 3 alloys. This readily results in the samples prepared by various processing ways displaying different Al 2 O 3 particle size and spatial distributions, Cu grain size distributions as well as dislocation densities. As a result, a total tensile elongation of over 10% and a tensile strength of approximately 600 MPa are attained in an extruded and rolled Cu-5vol.%Al 2 O 3 sample, which are difficult to obtain concurrently in the commercial Al 2 O 3 -dispersion-strengthed Cu materials prepared by internal oxidation. To understand these prominent mechanical combinations, we analyze and discuss the different tensile behaviors observed in the fabricated samples on the basis of their specific microstructural characteristics. • High extrusion ratio leads to finer Cu matrix and better spatial distribution of nanoscale Al 2 O 3 particles. • Secondary processing of hot rolling improves the dispersion of Al 2 O 3 particles and modifies the Cu matrix microstructures. • Rolled samples show enhanced ductility while maintaining strength in comparison with their corresponding as-extruded samples. • Microstructures and mechanical properties of ODS metallic materials can be tuned by extrusion ratio and secondary processing. [ABSTRACT FROM AUTHOR]