TA15合金基于变m值法超塑性研究

Superplasticity Study of TA15 Alloy Based on Variable m Value Method

基于变应变速率敏感性指数m值的方法对TA15合金超塑性进行了研究,在1053~1223 K温度范围内进行了超塑性拉伸实验。结果表明:TA15合金的延伸率为580%~1922%。微观组织分析表明合金变形过程中晶粒随温度升高而逐渐长大,但仍保持等轴状,在1223 K时发生α→β相转变,超塑性能严重下降。与恒应变速率法相比较,该方法大幅度提高了TA15合金的超塑性能。此外,超塑性变形过程中,力学性能和微观组织演变特征与Ashby-Verrall模型较吻合,因此推断出TA15合金基于变m值法超塑性变形的主要机制是扩散蠕变协调的晶界滑移。

Superplasticity of TA15 alloy was investigated based on the variable strain rate sensitivity exponent m value method.The superplastic tensile tests were conducted at 1053~1223 K.Results show that the elongation of TA15 alloy is 580%~1922%.The microstructure analysis shows that the grains are coarsened with increasing the temperatures but remain the equiaxed structure during the deformation.In addition,the phase transformationα→βoccurs at 1223 K,resulting in the serious reduction in superplastic property.Compared with that treated by the constant strain rate method,the superplasticity of TA15 alloy treated by the variable m value method is greatly enhanced.During the superplastic deformation,the mechanical properties and microstructure evolution are in good agreement with the Ashby-Verrall model.Therefore,it can be inferred that the dominant superplastic mechanism for TA15 alloy based on variable m value method is the grain boundary glide accommodated by diffusion creep.