TC21钛合金锻后热处理α片层的球化及强化增塑机理

Mechanism ofαlamellae spheroidization and strengthening plasticization of TC21 titanium alloy after post forging heat treatment

对经过最佳参数多向锻造(920℃-0.92单道次真应变-3周期-水冷)后的TC21钛合金进行球化热处理,并对多向锻造前、后及热处理后的试样进行了拉伸性能测试,研究了不同热处理工艺参数(温度830~920℃,保温时间1~4 h)下锻后合金α片层组织球化(等轴化)的演变规律,并揭示了合金的强化增塑机理。结果表明,配合920℃-0.92单道次应变量-3周期-水冷的多向锻造后的TC21钛合金较合适的球化热处理工艺参数为890℃-2 h-空冷。合适的球化热处理温度和保温时间能够促进TC21钛合金α片层的球化,经较佳参数锻造及后续热处理后的合金强度和塑性显著提升,屈服强度和伸长率分别达到894.0 MPa和13.2%。经球化热处理的TC21钛合金的强化增塑机理主要为α相晶粒细化引起的细晶强化及β相中析出的针状次生α相引起的位错强化。

TC21 titanium alloy was subjected to spheroidization heat treatment after multi-directional forging under optimal parameters(920℃-0.92 single pass true strain-3 cycles-water cooling),and the tensile properties of the specimens before and after forging and after spheroidization heat treatment were tested.The evolution law ofαlamellae spheroidization(equiaxation)under different heat treatment parameters(temperature of 830-920℃,holding time of 1-4 h)of the alloy was studied and the strengthening plasticization mechanism of the alloy was revealed.The results show that after optimal multi-directional forging,the preferred subsequent spheroidizing heat treatment parameters for the TC21 titanium alloy are 890℃-2 h-air cooling,which can promoteαlamellae spheroidization,and make that the yield strength and elongation of the TC21 titanium alloy are significantly improved,reaching 894.0 MPa and 13.2%,respectively.The strengthening plasticization mechanism of the TC21 titanium alloy after spheroidization heat treatment is mainly fine grain strengthening caused byαphase grain refinement and dislocation strengthening induced by needle-like secondaryαphase inβphase.