一种新型奥氏体不锈钢的塑性流变行为研究

Plastic Flow Behavior of a New Austenitic Stainless Steel AL6-XN under Different Strain Rates and Temperatures

在起始实验温度从 77K到 1 0 0 0 K,应变率从 0 .0 0 1 / s到 83 0 0 / s,并且使真实应变超过40 %条件下 ,对一种新型的氮增强奥氏体不锈钢 (AL6 - XN)进行了大量的单轴压缩实验。结果表明 ,这种材料在 77K低温下的真实应变可以达到 40 % ,并且它的韧性随着温度增加将会进一步显著提高 ;绝热剪切带或剪切破坏发生在大约 2 96 K温度以下 ;在较高温度下 ,明显的温度依赖性减弱反映其良好的焊接性能 ;动态应变时效发生在准静态及温度 5 0 0 K到 1 0 0 0 K之间。最后 ,一个发展的 Johnson- Cook本构模型 ,在不考虑动态应变时下被成功的用于预测这种 AL6 - XN的流变应力。

We performed a lot of uniaxial compression tests on a new austenitic stainless steel AL6 XN. In these tests, we reached true strains exceeding 40% under strain rates ranging from 0.001/s to 8 300/s and initial temperatures ranging from 77 K to 1 000 K with the final temperatures automatically ranging aproximately from 200 K to 1 100 K respectively due to heating of plastic deformation. These tests show that dynamic strain aging occurs at an initial temperature between 500 K and 1 000 K. Eq.(2) is the semi empirical Johnson Cook constitutive model. I found that (T ) m in eq.(2) is not quite satisfactory for predicting the plastic flow stress of AL6 XN and from my research experience, I propose to replace (T ) m with 0.9[(T-77)/(T m-77)] m . I determined experimentally the five constants in Johnson Cook model: τ 0 =500 MPa, B =2 000 MPa, C =0.04, 0 =0.000 1/s and m =0.4. For AL6 XN, eq.(2), after replacing (T ) m with 0.9[(T-77)/(T m-77)] m , finally becomes eq.(5). Figs.2 through 5 show that prediction with eq.(5) gives results in fairly good agreement with test data on AL6 XN.