9Ni钢中逆转变奥氏体的稳定性

为了研究逆转变奥氏体在应力和低温条件下的稳定性,通过透射电子显微镜对淬火+回火(QT)和淬火+两相区淬火+回火(QLT)处理9Ni钢中逆转变奥氏体进行形貌观察.结果发现QT处理钢中逆转变奥氏体以块状形态存在;QLT处理钢中逆转变奥氏体以块状和薄膜状存在,薄膜状逆转变奥氏体分布在板条边界上.通过X射线衍射对液氮浸泡前后逆转变奥氏体含量和其碳含量的变化进行测量,发现QLT工艺处理后在液氮中稳定存在的逆转变奥氏体的含量要高于QT工艺.通过三点弯曲试验、单轴拉伸和压缩试验研究其机械稳定性,发现拉应力和压应力均能促使逆转变奥氏体转变,大部分残留奥氏体分布在晶内.

Stability of reversed austenite in 9Ni steel

To evaluate the stability of reversed austenite under the condition of stress and low temperature,the morphologies of reversed austenite in 9Ni steel after the treatments of quenching + tempering(QT) and quenching + lamellar quenching + tempering(QLT) were observed by transmission electron microscopy.Reversed austenite in the QT-treated sample is most lath-like;but in the QLT-treated sample,both thin foil and lath reversed austenite can be discovered and the former mainly turns up along lath martensite.The amount of reversed austenite and its carbon content before and after soaking in liquefied nitrogen were measured by X-ray diffraction.More stable reversed austenite is detected in the QLT-treated sample after soaking in liquefied nitrogen.The mechanical stability of reversed austenite was gauged by bending,uniaxial tensile and compression tests.Both the tensile and compress stress promote the reversed austenite to transform,and most of residual austenite are revealed within grains.