超细晶钢微观组织与力学性能的各向异性研究

Study on anisotropy of microstructure and mechanical properties of ultrafine grain steel

通过温轧技术,成功制备了平均晶粒尺寸约1μm的超细晶钢。利用扫描电镜、电子背散射衍射和室温拉伸等检测手段,研究了超细晶钢板的微观组织与力学性能的各向异性。结果表明:制备的超细晶钢板不同方向的微观组织和力学性能具有明显的各向异性;纵截面表层和心部的晶粒大多呈现拉长的形态,同时表层的晶粒拟合椭圆长/短轴比相较于心部更小,形状更加接近于圆形,横截面的晶粒拉长状特征相较于纵截面减弱,更接近等轴态,晶粒在三维空间呈细长的扁梭形态;各向强度由高到低依次为轧向、横向、与轧向成45°方向;长梭形晶粒组成的微观组织形态和织构是导致超细晶钢板力学性能各向异性明显的主要原因。

An ultrafine grain steel with an average grain size of about 1μm was successfully prepared by warm rolling technology.Scanning electron microscopy,electron backscatter diffraction and room temperature tensile testing and other methods were used to study the anisotropy of the microstructure and mechanical properties of the ultrafine grained steel.The research results show that the microstructure and mechanical properties of the prepared ultrafine grained steel are obviously anisotropic.The grains in the surface layer and the core position of the longitudinal section are mostly elongated.At the same time,the aspect ratio of the grains in the surface layer is smaller than that in the core,and the shape is more like a circle.Compared with the longitudinal section,the elongated features of the grains in the cross section are weakened and the shape becomes more equiaxed.The grains should appear as slender and flat shuttle shapes in three-dimensional space.The mechanical properties of the prepared ultrafine grained steel are obviously anisotropic,in which the tensile strength from high to low is in rolling direction,transverse direction,and 45°to the rolling direction.The microstructure and texture composed of long spindle-shaped grains are the main reason for the obvious anisotropy of the mechanical properties of the ultrafine grain steel.