亚稳态材料的变形失稳及应力平台

DEFORMATION INSTABILITY AND STRESS PLATEAUIN METASTABLE MATERIALS

亚稳态的 Cr Ni系奥氏体不锈钢在 - 1 96℃拉伸应力应变曲线发现有弹塑性失稳与应力平台现象 ,试验结果表明应变率增加 ,εphεL 增大。 XRD分析证明弹塑性失稳点是应变诱发马氏体形成起始点 ,应力平台是形变硬化和相变软化在一定应变范围内达到动态平衡造成的 ,它与吕德斯带在试样中的传播有着本质的不同。测定计算得到 :产生单位体积分数马氏体相变所需的应变能 ,即相变能为 3.85× 1 0 6 J/ m3。

The elasto plastic instability and stress plateau have been found in the CrNi metastable austenite stainless steel at -196℃.The experimental results show that both ε ph and ε L increase with the strain rate increasing.XRD confirms that the elasto plastic instability stems from the strain induced martensite transformation.The Stress plateau that caused by the dynamic balance between the strain hardening and the phase transformation softening in a certain range of strain is essentially different from Luders band propagation in the sample.The measurement and calculation show that the strain energy,i.e.,the phase transformation energy for production of per unit volume fraction of martensite,maintains constant in the stage of both elasto plastic instability and stress plateau,which is 3.85×10 6J/m 3.