5CrNiMoV钢马氏体相变塑性和应力对其相变动力学的影响

Transformation plasticity of martensite of 5CrNiMoV steel and effect of stress on its kinetics

利用DIL-805ADT动态相变膨胀仪测定了5CrNiMoV钢在低于奥氏体屈服强度的应力下的马氏体相变膨胀曲线,根据膨胀曲线分析并计算出了不同应力下Greenwood-Johnson相变塑性机制中的相变塑性系数k值和Koistinen-Marburger马氏体相变动力学模型中α和Ms的值,并且将Greenwood-Johnson模型和Leblond模型计算结果与实际试验值对比。结果显示:k值随应力的变化有所波动,但趋近于一个定值;通过对比,Leblond模型更符合试验结果;Ms点随着应力的增大呈现微小的上升趋势,说明小于或等于80 MPa的应力对Ms点的影响不显著;拉应力下α值普遍大于无应力下的α值,压应力下α值普遍小于无应力下的α值,说明拉应力对相变有一定的促进作用,压应力对相变有一定的阻碍作用。

Axial expansion and contraction martensite transformation in 5 CrNiMoV steel under uniaxial stresses lower than the yield strength of austenite were measured by means of DIL-805 ADT dynamic dilatometer.Kinetic constantsαand Ms in the Koistinen-Marburger equation for martensite transformations were simultaneously determined along with the transformation plasticity coefficient k in Greenwood-Johnson transformation mechanism from the dilation data.Transformation plasticity coefficient and the Greenwood-Johnson model and Leblond model calculation results were compared with the actual test values.The result is that the value of k fluctuates with the change of stress,but approaches a fixed value.The Leblond model is more in line with the test results by contrast.The Ms shows a slight upward trend with the increase of stress,and it shows that the effect of stress lower than or equal to 80 MPa on the Ms is not significant.Theαunder tensile stress is slightly higher than that under no stress,andαunder compressive stress is slightly lower than that under no stress,indicating that tensile stress promotes transformation and compressive stress hinders transformation.