Effect of chemical composition and heat treatment on microstructure and mechanical properties of Nb-xTi-16Si–3Cr–3Al-2Hf-yZr alloy

Abstract In this paper, four Nb-xTi-16Si–3Cr–3Al-2Hf-yZr (x + y = 20) alloys prepared by arc-melting furnace with non-consumable tungsten electrode, which was heat-treated at 1400 °C/50 h in argon atmosphere. The microstructures of the as-cast alloys and the heat-treated alloys were observed, and the room temperature fracture toughness and the hardness were tested. The results indicated that with the increase of Zr content, γ-Nb 5 Si 3 phase appeared in as-cast alloys with an increasing volume fraction. After heat treated, the microstructures of the alloys were finer, and the transformation from γ-Nb 5 Si 3 to α-Nb 5 Si 3 occurred. In addition, the room temperature fracture toughness and hardness of the heat-treated alloys are higher than those of as-cast alloys. For heat-treated alloys, the room temperature fracture toughness presented a slight downtrend followed by an uptrend with increase proportion of Zr, however the hardness was being improved. By contrast, for as-cast alloys the toughness and the hardness decreased.