纳米/超细晶18Cr-8Ni奥氏体不锈钢力学性能及变形机制

Mechanical properties and deformation mechanism of nano/ultrafine-grained 18Cr-8Ni austenitic stainless steel

采用应变诱发马氏体退火逆相变的方法制备了18Cr-8Ni奥氏体不锈钢的纳米/超细晶组织,并对其力学性能和变形机制进行了分析。通过对奥氏体不锈钢进行室温轧制(压下率为70%)以及分别进行710℃×10 min,760℃×5 min和950℃×5 min的退火处理来获得不同晶粒尺寸的组织。结果表明:纳米/超细晶的平均晶粒尺寸为400 nm,屈服强度为878 MPa,伸长率为33%。对粗晶和纳米/超细晶钢的变形行为进行研究发现,纳米/超细晶钢断口处的显微组织存在大量的应变诱发马氏体和少量的孪晶。然而,在粗晶钢的断口处观察到了应变诱发马氏体、高密度位错和剪切带组织。

The nano/ultrafine-grained microstructure of 18Cr-8Ni austenitic stainless steel was prepared by strain-induced martensite phase reversion annealing, and its mechanical properties and deformation mechanism were analyzed. The austenitic stainless steel was cold-rolled(reduction rate of 70%) at room temperature and annealed at 710 ℃ for 10 min, at 760 ℃ for 5 min and at 950 ℃ for 5 min, respectively, to obtaine the strueture with different grain sizes. The results show that the average grain size of nano/ultrafine grain steel is 400 nm, the yield strength is 878 MPa, and the elongation is 33%. The deformation behaviors of the coarse-grained and the nano/ultrafine-grained steels were studied. It is found that there are a large number of strain-induced martensite and a small amount of twins at the fracture of the nano/ultrafine grained steel. Whereas, the strain induced martensite, high density dislocations and shear band structure are observed at the fracture of the coarse-grained steel.