The mechanical properties and thermal stability of a nanostructured carbide dispersion strengthened W-0.5 wt.% Ta-0.01 wt.% C alloy

Abstract

In this paper, W-0.5wt.% Ta-0.01wt.%C (W-05Ta-001C) alloys were fabricated via a combination of high energy ball milling and subsequent spark plasma sintering. The W-05Ta-001C alloys showed high strength of 565MPa at 400°C with a total elongation of 54%. The improved ductility resulted from nanosized TaC precipitation. The microstructure analysis of W-05Ta-001C alloys indicate that the nanosized TaC precipitation uniformly distributed in the grain interior encouraging trapping dislocations. TaC could reduce free oxygen concentration and thus enhance grain boundaries strength by reacting with impurities of oxygen to form compounds of Ta-Cx-Oy at grain boundaries. The thermal stability of W-05Ta-001C alloys was investigated by analyzing the evolution of hardness based on isochronal annealing tests. The results showed that hardness only slightly decreased with increasing annealing temperature up to 1500°C, and the recrystallization temperature was about 1600°C. This good thermal stability is attributed to nanosized TaC dispersion strengthened structures.