冷变形对高氮奥氏体不锈钢组织与力学行为的影响

EFFECTS OF COLD DEFORMATION ON MICROSTRUCTURE AND MECHANICAL BEHAVIOR OF A HIGH NITROGEN AUSTENITIC STAINLESS STEEL

通过对氮含量为1．2%的高氮奥氏体不锈钢施加不同变形量的压缩变形,研究了冷变形对高氮钢的组织和力学行为的影响．结果表明,高氮钢在最高变形量达到56%时的冷变形过程中未发现有α′马氏体形成．高氮钢在变形初期孪晶和滑移共同参与变形,孪晶对滑移有强烈的阻碍作用．随变形量的增加,孪晶受到滑移线的切割,孪晶界不再清晰．高氮钢的加工硬化指数随变形量增加而降低．当冷变形至56%时,高氮钢的屈服强度提高了约2倍,抗拉强度提高了约1倍．分别达到1645MPa和1870MPa．对比分析氮在几种奥氏体不锈钢中的作用表明,氮通过短程有序排列的方式阻止位错的滑移,提高了高氮钢的加工硬化能力．

The influences of cold deformation on the microstructure and mechanical behavior for a high nitrogen austenitic stainless steel （1.2%N） were investigated through cold-rolling to different thickness reductions. No deformation-induced α′ martensite was found in the steel even deformed up to 56%. It was found that the mechanical twins and dislocations slipping were the main deformation mechanism at the initial deformation stage, and the slipping was strongly obstructed by the twins. With increase of the deformation, the twins were split by slipping lines, and the twin boundaries were blurred. The strain-hardening exponent decreased with increase of the deformation. When the deformation reached to 56%, the yield strength and ultimate tensile strength were increased by about two times and one time, reached to 1654 MPa and 1870 MPa, respectively. By comparing the roles of nitrogen in several austenitic stainless steels, it was suggested that nitrogen obstructs the dislocations slipping and enhances the strain-hardening ability through the short range ordering.