考虑相变和温升效应的奥氏体不锈钢本构方程

Constitutive equation of austenitic stainless steel considering phase transformation and temperature rise effect

为探究温升和应变速率对奥氏体钢拉伸过程中相变的影响,选用AISI 301LN-1/4H不锈钢进行了不同应变速率下的温升观测实验和准静态下应变受控的拉伸实验,发现材料在拉伸变形的弹性阶段,由于热弹效应的影响,标距段内温度略微下降(约为0.35℃);颈缩阶段的热成像图能够准确预测变形过程中的失效区域。在应变速率效应和温升效应的共同作用下,奥氏体不锈钢的极限拉伸强度显示为应变率负相关性。对不同应变的回收试样进行了EBSD观测,构建了马氏体相变的JMAK模型。最终结合所得的相变模型和温升观测实验结果构建了考虑相变和温升效应的奥氏体不锈钢本构方程。结果表明,奥氏体向马氏体(γ→α′)转化的最低应变为0.05,拟合的应力曲线可以较好地反映应力在进入塑性应变以后的增长。

To explore the influence of temperature rise and strain rate on the phase transformation of austenitic steel during tensile process, AISI 301 LN-1/4 H stainless steel was selected to conduct temperature rise measurement experiments with different strain rates and strain-controlled tensile experiments under quasi-static condition. It is found that in the elastic stage of tensile deformation, due to the influence of thermal elasticity effect, the temperature in gauge length section decreases slightly(about 0.35 ℃);the thermal imaging figure can accurately predict the failure area during deformation process at necking stage. Under the combined action of strain rate effect and temperature rise effect, the ultimate tensile strength of austenitic stainless steel shows negative correlation with strain rate. EBSD observation of recycled samples with different strains was carried out, and JMAK model of martensite phase transformation was constructed.Finally, combining with the obtained phase transformation model and the experimental results of temperature rise observation, the constitutive equation of austenitic stainless steel considering phase transformation and temperature rise effect was constructed. The results show that the minimum strain of transformation from austenite to martensite(γ→α′) is 0.05, and the fitted stress curves can well reflect the growth of stress after entering plastic strain.