热变形TiAl基合金的超塑性行为

SUPERPLASTICITY BEHAVIORS OF THERMALLY DEFORMED TiAl BASED ALLOYS

采用包套锻复合热机械处理技术，在Ti-33Al-3Cr合金中得到了平均名义晶粒尺寸为1μm的热变形显微组织材料在1000—1075℃及10×10－6—8×10－3S－1的应变速率范围内显示良好的超塑性，其应变速率敏感系数高达0．9；热激活能仅为250kJ／mol．在1075℃及8×10－5s－1下得到517％的超塑性拉伸延伸率．获得高的超塑性拉伸值的机理是。

Superplasticity behaviors under the conditions of a temperature range from 1000℃ to 1075℃ and strain rates varlying from 1×10-6 to 8×10-3 s-1 were investigated for Ti-33Al-3Cr alloy with 1 μm grain size obtained by multi-step thermal mechanical treatment. Test results show that this TiAl alloy possesses good superplasticity. It exhibits a strain rate sensitivity coefficient of 0.9 at the strain rate of 3×10-4 s-1 and temperatures from 1000℃ to 1075℃. Tensile elongation of 517% was obtained at the temperature of 1075℃ and the strain rate of 8×10-5 s-1. Test results also show that this alloy has a low thermal activation energy of about 250 kJ/mol. Superplasticity behavior obtained from this fine-grained TiAl is due to dynamic recrystallization during tensile deformation.