奥氏体不锈钢晶粒细化对形变机制和力学性能的影响

利用相逆转变原理采用冷变形使得亚稳奥氏体转变为形变马氏体,采用不同温度和时间退火分别获得纳米晶/超细晶和粗晶奥氏体不锈钢。通过拉伸实验得到不同晶粒尺寸的奥氏体不锈钢力学性能,采用透射电镜观察形变组织结构并利用扫描电镜观察断口特征。结果表明:高屈服强度纳米晶/超细晶奥氏体不锈钢通过形变孪晶获得优良塑性;而低屈服强度的粗晶奥氏体不锈钢发生形变诱导马氏体效应,得到良好的塑性;两组具有不同形变机制的奥氏体不锈钢拉伸断口均为韧性断裂。形变机制由形变孪晶转变为形变诱导马氏体归因于晶粒细化导致奥氏体稳定性大幅度提高。

Effect of Grain Refinement on Deformation M echanism and M echanical Properties of Austenitic Stainless Steel

T he concept of phase reversion involving cold deformation of metastable austenite to gener‐ate strain‐induced martensite ,followed by temperature‐time annealing sequence ,was used to obtain grain size of nanograined/ultrafine‐grained and coarse‐grained austenitic stainless steels .The mechani‐cal properties of austenitic stainless steels with different grain sizes were obtained by tensile testing , the deformation microstructure and fracture surface were analyzed by TEM and SEM observations ,re‐spectively .The results indicate that deformation twins contribute to excellent ductility in high yield strength nanograined/ultrafine‐grained steel ,while in the low yield strength coarse‐grained steel ,the high ductility is due to strain‐induced martensite transformation .Interestingly ,the tensile fracture of the two austensite stainless steels with different deformation mechanism is ductile fracture .The de‐formation mechanism from deformation twins to strain‐induced martensite in the coarse‐grained struc‐ture in nanograined/ultrafine‐grained structures is owing to the increased stability of austenite with grain refining .