化学成分对316L奥氏体不锈钢组织及变形行为的影响

Effect of chemical composition on microstructure and deformation behavior of 316L austenitic stainless steel

利用万能试验机对不同镍当量(Nieq)的316L不锈钢热轧钢板进行常温单轴拉伸试验,借助扫描电镜(SEM)和透射电镜(TEM)对其拉伸变形前后的微观组织进行观察,探索镍当量对316L不锈钢微观组织及性能的影响规律。结果表明,固溶态试验钢的组织均为奥氏体组织及少量高温δ相,强度随Nieq的升高而降低,塑性和韧性随Nieq升高而增加;拉伸断口均呈韧性断裂特征,且随Nieq的提高,韧窝的数量减少,韧窝尺寸增加;TEM显示,变形后的试验钢均未发生马氏体相变,Nieq较低时,变形量大的地方位错密度高,发生位错交互作用,局部有形变孪晶生成,且随着Nieq的增加,形变孪晶密度增大,出现相互交叉、阻滞。

Room temperature uniaxial tensile test was carried out by universal testing machine for hot-rolled 316 L stainless steel plate with different nickel equivalents, then microstructure of the steel before and after the tensile deformation was observed by scanning electron microscope(SEM) and transmission electron microscope(TEM), and the effect of nickel equivalent(Nieq) on microstructure and properties of 316 L stainless steel was explored. The results show that the microstructure at solid solution state is austenite and a small amocmt of high temperature δ phase, the strength decreases with the increase of Nieq, and the plasticity and toughness increase with the increase of Nieq. The tensile fracture is characterized by ductile fracture, and with the increase of Nieq, the number of dimples decreases while the size of dimples increases. The TEM observation shows that no martensitic transformation occurs in the deformed tested steel, when the Nieq is low, the dislocation density in the place with large deformation is high, dislocation interaction occurs, and deformation twins are formed locally. With the increase of Nieq, the density of deformation twin increases, and resulting in crossing and hysteresis.