The microstructure and strength of a tantalum alloy: Influence of temperature

Tantalum-tungsten alloys are considered as potential materials used in high temperature applications due to their exceptional mechanical properties. To evaluate the mechanical properties of tantalum-tungsten alloys at elevated temperatures, a binary tantalum alloy containing 4 wt% tungsten (Ta–4%W) was chosen and their mechanical properties were tested at 1400–2000 °C, respectively, with the aid of a homemade coupled thermal-mechanical material testing system. The results show that the ultimate tensile stress, the yield stress and the uniform elongation gradually decrease, while the total tensile elongation keeps constant as the test temperature increases. Ta–4%W alloy have continuous work hardening capability at ultrahigh temperature even up to 2000 °C. The microstructural observations show that grain size increase and dislocation density decrease rapidly when the test temperature was increased to 1800 °C and 2000 °C. Furthermore, the dislocation substructure and dislocation types at elevated temperatures were analyzed and found to be distinctly different from that at room temperature. Base on the model between quantitative microstructural parameters and strength, the flow stress was calculated utilizing additive law from the microstructures with the structural morphology and related quantitative parameters. Mechanical strength loss of Ta–4%W at elevated temperature was evaluated after comparing the calculated and experimentally measured values.