A high-density non-equiatomic WTaMoNbV high-entropy alloy: Alloying behavior, microstructure and mechanical properties

Abstract

A bulk fine-grained W35Ta35Mo10Nb10V10 (at%) high-density high-entropy alloy (HEA) was successfully fabricated by mechanical alloying (MA) and spark plasma sintering (SPS) with varying parameters. Microstructure evolution and mechanical behavior of the HEA samples in various processing conditions were investigated. The alloying effect in the mixed high-purity powders becomes more significant as the increase of ball milling time during MA. Upon SPS at various temperatures ranging from 1600 to 1800 °C, a supersaturated body-centered-cubic (BCC) matrix prevails with the precipitation of Ta2VO6 oxides. After SPS at 1700 °C for 10 min, the average mass density, ultimate compressive strength and microhardness of the bulk HEA at room temperature are 14.65 g cm−3, 2519 MPa and 6.50 GPa, respectively. The mechanisms responsible for the high strength and hardness include massive substitutional solid solution strengthening by the alloying of multiple principal elements, grain boundary strengthening, precipitation strengthening by Ta2VO6 particles, and interstitial solid solution strengthening by interstitials (e.g., tramp O from processing) in the matrix. The systematic information on the relationships among processing parameters, alloy densities, microstructure characteristics (e.g., grain sizes, volume fractions and sizes of precipitated oxides) and mechanical properties provide useful insights for the development of novel high-density and high-strength materials.