The Influence of the Deformation and Heat Treatment on the Structure and Heat-Resistance of Ti–Al–Zr–Si Alloys

Abstract

The heat-resistant Ti–Al–Zr–Si alloys (base Ti–(6–7)Al–(2–3) Zr–(1–1.5)Si and additionally alloyed Ti–(6–7)Al–(3–5)Zr–(1–1.5)Si–(2–4)Sn), obtained by electron beam smelting were studied. Deformation was carried out in the β- or upper part of the (α+β)-area by means of forging and rolling into a strip. The base alloy was subjected to rolling in the upper part of the α+β-area, and the fine-grained uniform structure with a grain size of 10–20 μm was obtained. Internal stresses and defective substructure of the deformed alloy intensify the decomposition of the solid solution and promote the formation of evenly distributed dispersed silicides, which allows obtaining high strength and heat resistance characteristics. Tensile tests at 20; 650 and 700°C of the Ti–(6–7)Al–(2–3)Zr–(1–1.5)Si alloy samples after deformation and annealing also showed a rather high level of the tensile strength and yield strength. After 20 h exposure at the operating temperature of 700°C, the structure becomes more equilibrium, due to which the strength of the deformed alloy decreases, and the relative elongation increases. Additional alloying of the base alloy with zirconium and tin slightly increases plasticity and decreases heat-resistant properties.