热轧及热处理对Ti_(2)AlNb合金板材显微组织及力学性能的影响

Effect of hot rolling and heat treatments on microstructure and mechanical properties of Ti_(2)AlNb alloy plates

针对热轧后Ti_(2)AlNb基合金板材性能差,难以进一步实施冷轧的问题,本文将热轧后的板材进行不同相区的热处理,并对热轧及热处理后的显微组织及力学性能进行了系统的研究。结果表明:不同相区热处理后的显微组织内部变化差异较大。在较低温度热处理时α_(2)相含量增多,而在高温热处理时α_(2)相含量略微减少。随着热处理温度的升高,从B2相中析出的针状O相发生球化现象;且显微组织内部小角度晶界逐渐减少,位错密度也逐渐减小,而等轴状的再结晶晶粒增多。试样的织构分析表明,由于择优取向,热处理后B2相织构也发生了较大的变化,热轧后的{115}〈110〉织构组分向{001}〈110〉旋转立方织构转变,而{111}〈112〉织构组分随热处理温度的升高不断增强。随着热处理温度的升高,板材室温拉伸强度逐渐降低,伸长率则不断提高。经(1020℃,1 h,WQ)热处理后,板材屈服强度和伸长率分别为962 MPa和9.34%,较轧态试样分别降低12.3%和提高239.6%。这主要归因于O相的球化、α_(2)相体积分数降低、位错密度减小以及再结晶的共同作用。

In view of the poor properties of Ti_(2)AlNb-based alloy plates after hot-rolling and the difficulty of further implementing cold-rolling,this paper subjected the hot-rolled plates to heat treatment in different phase zones and conducted a systematic study of the microstructure and mechanical properties after hot-rolling and heat treatment.The results show that heat treatment causes significant variations in microstructure across different phase zones.Theα_(2)phase content increases at lower temperature heat treatments and slightly decreases at higher temperature heat treatments.As the temperature of the heat treatment increases,the needle-like O phase precipitates from the B2 phase globuring;the dislocation density reduces within the microstructure and the number of equiaxed recrystallized grains increases.The texture analysis of the specimens shows that the B2-phase texture also changes significantly after heat treatment due to the preferential orientation,with the{115}〈110〉texture component formed after hot rolling shifting to the{001}〈110〉rotating cubic texture,while the{111}〈112〉texture component is continuously enhanced with the increase of heat treatment temperature.As the heat treatment temperature increases,the plate’s tensile strength at room temperature decreases but the elongation improves.After(1020℃,1 h,WQ)heat treatment,the yield strength and elongation are 962 MPa and 9.34%,respectively,12.3%lower and 239.6%higher than those of the rolled state specimens.This is primarily attributable to the combined effects of spheroidization of the O phase,reduction ofα_(2)phase volume fraction,reduction of dislocation density,and recrystallization.