高强TRIP钢的显微组织及动态力学行为

Microstructure and dynamic deformation behavior of high strength TRIP steel

采用CCT-AY-Ⅱ型钢板连续退火机对高强TRIP钢进行热处理,获得铁素体、贝氏体,残留奥氏体和少量马氏体的组织。采用SEM、EBSD等微观方法观察制备的TRIP钢的微观组织,利用XRD法测量了残留奥氏体量,实验测量了其力学性能。结果表明:820℃两相区退火,410℃贝氏体区后实验钢获得良好的综合力学性能,屈服强度达到804 MPa,抗拉强度928 MPa,总伸长率27.55%,强塑积25.57 GPa·%。这主要是退火后实验钢合适的相比例以及一定量残留奥氏体共同作用的结果;实验钢在高速拉伸下,应力随应变的增加而增加,实验钢在高速下表现出良好的力学性能,不仅具有很高的强度,而且表现出良好的塑性,高速下实验钢良好的力学性能是因为钢中大量残留奥氏体发生TRIP效应造成的。

Multiphase microstructure which consists of ferrite,bainite,retained austenite and a few martensitein was obtained in a high strength TRIP steel by interitical annealing and bainite austemping on a CCT-AY-Ⅱtype continuous annealing simulator. Microstructure of the steel was observed by means of SEM and EBSD technique. The amount of retained austenite in the steel was determined by X-ray diffraction and its mechanical properties were measured. The results indicate that the tested steel sheet exhibits good comprehensive properties with yield strength of 804 MPa,tensile strength up to 928 MPa and total elongation A50 of 27. 55%,and the product of tensile strength and elongation is 25. 57 GPa·%,after intercritical annealing at 820 ℃ and bainitic austempering at 410 ℃ due to the refined microstructure,appropriate proportion of phases and a specific proportion of retained austenite. The stress increases with the increase of the strain for the steel under high speed tensile loading,which shows a good combination of shrength and plasticity. The good mechanical performance of the steel under high speed tensile test is ascribed to the TRIP effect of the large amount of residual austenite in the steel