30 GPa·%级中碳贝氏体钢中残余奥氏体的调控机理

Mechanism of residual austenite in medium-carbon bainite steel of 30GPa·% level

为了进一步提高中碳贝氏体钢的强塑性能,研究残余奥氏体的形态及分布对中碳贝氏体钢强塑积的影响。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)等测试技术对不同试样的显微组织进行观测对比,利用X射线衍射测试技术(XRD)对试样的组织含量进行检测,利用拉伸试验对试样的力学性能进行检测。结果表明,Al部分取代Si能够加速贝氏体相变过程,有效细化贝氏体板条尺寸和残余奥氏体尺寸,提升残余奥氏体中的碳含量,促使形成更稳定的尺寸更小的薄膜状残余奥氏体,推迟试样颈缩的发生,试样伸长率有大幅度的提升。其中,300℃等温淬火8 h工艺条件下,0.26Si-1.1Al试样的强塑积提升至30 GPa·%级别。

The purpose of this experiment was to study the influence of the shape and distribution of residual austen-ite on the product of strength and ductility of medium-carbon bainite steel to further enhance the strength and ductili-ty of the medium-carbon bainite.Testing techniques such as scanning electron microscope(SEM)and transmission electron microscope(TEM)were used to test different samples for comparison of the microstructure.XRD was used to detect the content of the samples.Tensile test was used to test mechanical properties of the samples.The results showed that the partial replacement of Si by Al could accelerate the bainite transformation process,which could also effectively refine the bainite lath and the residual austenite size.Besides,the partial replacement of Si by Al increased the carbon content in the residual austenite which promoted the formation of film residual austenite.Thus,necking of the samples was delayed.Finally,the elongation of the samples was greatly improved.The strength-ductility of 0.26Si-1.1Al samples under the process of isothermal annealing at 300℃for 8h was raised to the level of 30GPa·%.