Effect of hot rolling and annealing on the mechanical properties and thermal conductivity of W–0.5wt.% TaC alloys

The mechanical properties and thermal conductivity of W-0.5wt.% TaC alloys prepared by spark plasma sintering as well as ordinary sintering followed by hot rolling and annealing treatment, respectively, were investigated. Tensile tests indicate that below 600°C there is no tensile plastic deformation while at 700°C the total elongation of spark plasma sintered (SPSed) W-0.5wt.% TaC is up to 36%, which is about 3.3 times that of spark plasma sintered W samples. In contrast, the tensile strength and total elongation of rolled W-0.5wt.% TaC are 717MPa and 10.7% at 250°C, respectively. The ductile-brittle transition temperature (DBTT) of rolled W-0.5wt.% TaC is between 200°C and 250°C, about 300°C lower than that of spark plasma sintered W-0.5wt.% TaC (~600°C). Annealing decreases the DBTT (~200°C) and improves thermal conductivity from 175 to 186W/m·K at room temperature. Microstructure analyses indicates that TaC could purify and strengthen grain boundaries by capturing impurity oxygen in tungsten to form Ta2O5. The results indicate that strength, ductility and thermal conductivity can be improved by purifying, hot rolling and subsequent annealing.