Search

Abstract The performance of tungsten heavy alloys (WHAs) is related to the characteristic of matrix/W interfaces, which depends directly on the wettability of the matrix materials on W. This work designs a novel WHA that selects an AlCrFeNiV-system high entropy alloy (HEA) as matrix based on its wetting behavior on polycrystalline W. The wetting experiments show that this W/HEA system exhibits low contact angles at the temperatures for liquid phase sintering (LPS), and dissolutive wetting with a moderate W solubility in the HEA. This favorable wetting behavior benefits the densification process during LPS, leading to clean matrix/W interfaces with high bonding strength and hence a high ultimate tensile strength of 1132 MPa in the resulting W/HEA composite. These results indicate that the AlCrFeNiV-system HEA is a promising matrix material for WHAs. Graphical abstract Image 1 Highlights • A novel tungsten heavy alloy using high entropy alloy as matrix (W/HEA composite) is prepared by liquid phase sintering. • Dissolutive wetting of W by HEA melt with low contact angles is investigated. • W/HEA composite has fine W particle size of 13.15 μm and strong interfacial bonding. • W/HEA composite has a high yield strength of 705 MPa and high ultimate tensile strength of 1132 MPa. [ABSTRACT FROM AUTHOR]

Deformed alloys commonly soften after annealing because of the decrease in defects. This work reports an annealing hardening that occurs in a cryo-rolled CoCrFeNi high-entropy alloy. This abnormal behavior is related to continuous twinning in nanoscale, which would have occurred in cryo-rolling but was belated until annealing was performed. This is because the stress accumulated in cryo-rolling was not enough to activate the reaction between dislocations and stacking faults, so as to require additional thermal activation (by annealing) for supplying the energy requirement for twinning. Due to the extra strengthening from stable twin boundaries, the annealed samples exhibit an ultrahigh yield strength close to 1.4 GPa (~6 times higher than the solid-solution counterpart), even after annealing for 24 h. These results confirm a possibility for introducing numerous stable nanotwins in bulk FCC metals to improve their mechanical properties. [ABSTRACT FROM AUTHOR]

Coherent ordered nanoprecipitation (CON) hardening is an efficient strategy for breaking the strength-ductility trade-off. Revealing the precipitation mechanism and its influence on mechanical property is significant for further optimization of CON-strengthened alloys. In this work, we investigated the precipitation and mechanical behavior of the coherent FCC/L1 2 spinodal nanostructure and nano-lamellar BCC phase in a newly developed CON-strengthened Al 0.5 Cr 0.9 FeNi 2.5 V 0.2 high entropy alloy (HEA). We found that high-density defects induced by pre-deformation promoted the segregation of Cr, resulting in composition redistribution. The thermodynamics state of the matrix shifted into a spinodal regime and the ordering energy of L1 2 phase increased, facilitating the formation of coherent FCC/L1 2 spinodal nanostructure. Meanwhile, the Cr segregation promoted the precipitation of Cr-enriched nano-lamellar BCC phase. During tensile deformation, the FCC phase yielded first, followed by L1 2 and BCC phases in sequence. The L1 2 and BCC strengthening phases contributed to an ultrahigh macroscopic yield strength. Due to the low-misfit interconnected spinodal nanostructure, the differences in phase stress between FCC and L1 2 phases was insignificant, which could avoid the stress concentration and retain ductility. The nano-lamellar feature of the stiff BCC phase delayed the crack initiation and propagation. Our research revealed not only the significant effect of pre-deformation on CONs formation and refinement, but also the deformation mechanism of CONs, which shed new light on the microstructural optimization and mechanical property improvement of CON-strengthened alloys. [Display omitted] [ABSTRACT FROM AUTHOR]