锻态Ti-44Al-4Nb-4V-0.3Mo-Y合金等轴及片层组织高温拉伸性能及组织演变

Tensile properties and microstructural evolution of hot forged Ti-44Al-4Nb-4V-0.3Mo-Y alloy with equiaxed and lamellar microstructure during high temperature tension

摘要:

等轴γ晶粒和α2/γ片层是beta-gamma TiAl合金的两种主要变形组织形态。本文研究了锻态Ti-44Al-4Nb-4V-0.3Mo-Y合金等轴组织及片层组织的高温拉伸性能及组织演变。结果表明：拉伸温度对Ti-44Al-4Nb-4V-0.3Mo-Y合金的力学性能和显微组织有显著的影响。在相同温度下，Ti-44Al-4Nb-4V-0.3Mo-Y合金等轴组织的抗拉强度和屈服强度略高于片层组织，而延伸率相差不大。随拉伸温度的增加，合金的抗拉强度和屈服强度逐渐减小，而延伸率迅速增大。对于等轴组织，提高温度，等轴γ晶粒被拉长，发生完全的动态再结晶，从而细化合金的显微组织。对于片层组织，α2/γ片层的分解和γ板条的再结晶程度随拉伸温度的增加而增大。Ti-44Al-4Nb-4V-0.3Mo-Y合金的韧脆转变温度在750～800℃之间。

Abstract:

The equiaxed γ grains and α2/γ laminas are the two main deformed microstructure of beta-gamma TiAl alloy. In this paper, mechanical properties and microstructural evolution of hot forged Ti-44Al-4Nb-4V-0.3Mo-Y alloy with equiaxed and lamellar microstructure were studied during high temperature tension. The results show that tensile temperature has a significant effect on the mechanical properties and microstructures of Ti-44Al-4Nb-4V-0.3Mo-Y alloy. At the same temperature, the tensile strength and yield strength of the TiAl alloy with equiaxed microstructure are slightly greater than those with lamellar structure，however the elongation difference is not significant. With the increase of tensile temperature, the tensile strength and yield strength of TiAl alloy decrease gradually, while the elongation increases significantly. For equiaxed microstructure， increasing tensile temperature, the equiaxed γ grains are elongated and complete dynamic recrystallization occurs to refine the microstructure of the TiAl alloy. For lamellar microstructure, the degree of decomposition of α2/γ laminas and recrystallization of γ laths increase with the increase of tensile temperature. The ductile brittle transition temperature of Ti-44Al-4Nb-4V-0.3Mo-Y alloy is between 750 ~ 800°C.