Influence of Sintering Temperatures on Microstructure Evolutions and Mechanical Properties of W-CoFeNi Tungsten Heavy Alloys
摘要
W-CoFeNi WHAs (tungsten heavy alloys) were fabricated by powder metallurgy with sintering temperatures ranging from 1 480 to 1 560 °C. The influence of sintering temperatures on microstructure evolutions and mechanical properties of W-CoFeNi WHAs was investigated. The experimental results show that near-spherical W grains are distributed in CoFeNi ternary multi-principal-elements alloy (MPEA) with the formation of W-rich μ phase in all W-CoFeNi WHAs. The volume fractions of μ phase and average W grain size increase with sintering temperatures changing from 1 480 to 1 560 °C. The activation energy for W grain growth is significantly higher than that of traditional W-Ni-Fe and W-Ni-Co WHAs, which indicates grain coarsening behavior in CoFeNi MPEA became more difficult compared to the conventional binder alloys. W-CoFeNi sintered at 1 480 °C exhibits the highest yield strength of 698 MPa among all WHAs due to finer W grain size. The compressive strength and fracture strain of W-CoFeNi reduce when sintering temperatures rise from 1 480 to 1 560 °C.