低碳钢表面剧烈形变与回复热处理诱发合金化研究

Alloying induced by severe deformation and recovery treatment on low-carbon steel surface

利用光学显微镜、扫描电子显微镜、能谱仪、X射线衍射仪、显微硬度计研究剧烈形变和低温回复处理对低碳钢表面Cr合金化的梯度组织结构和力学性能的影响。结果表明,采用机械剧烈冲击形变和低温回复处理能够在低碳钢表面形成具有梯度组织结构的含Cr合金化层,含Cr相主要为Fe-Cr固溶体和碳化物(Cr,Fe)_7C_3,且硬度从心部145 HV1逐渐向表层提高到215 HV1,这是由于应力增加导致晶体结构缺陷增多,同时应力引起温度升高以及后续的低温回复热处理过程中,在应力-热耦合效应的共同作用下,Cr元素扩散系数增加,加速扩散,促进合金化,形成梯度组织结构,显著改善和提高原材料的组织和力学性能。

Effect of surface severe deformation and recovery treatment on gradient microstructure and mechanical properties of Cr alloying on low-carbon steel surface were investigated by using optical microscopy,scanning electron microscopy,energy dispersive spectroscopy,X-ray diffraction and micro-hardness tester. The results show that using severe mechanical punching deformation and recovery treatment can make Cr element diffuse into the surface of the low-carbon steel,which result in the formation of a gradient microstructure containing Cr alloying layer. The alloy phase are mainly Fe-Cr solid solution and（ Cr,Fe）_7C_3 carbide. From the matrix to surface,the hardness gradually increases from 145 HV1 to 215 HV1. This is because there is an increase in defects in the crystal structure,temperature due to stress increasing and recovery treatment, which rises Cr element diffusion coefficient, accelerates alloying, which promote the formation of a gradient microstructure. As a result,the microstructure and mechanical properties are significantly improved.