研究了连续柱状晶组织CuNi10Fe1Mn合金板试样沿平行柱状晶生长方向(SD)和垂直柱状晶生长方向(PD)拉伸时的力学性能和变形行为, 讨论了连续柱状晶组织各向异性对合金力学性能和变形行为的影响. 研究结果表明: 试样沿SD和PD均具有[100]择优取向, 但沿SD所有晶粒的取向均分布于[100]附近, 平均Taylor因子m值约为2.17, 而沿PD部分晶粒的取向分散于[001]-[011]之间, 具有一定的取向分散性, m值约为2.93. 低取向分散性、无横向晶界约束等组织特征使试样沿SD变形时应力分布均匀, 各晶粒沿拉伸方向变形一致, 屈服强度和抗拉强度分别为85和215 MPa, 断后伸长率达到42%, 具有典型韧性断口; 由于存在一定的取向分散性和横向晶界, 使得PD试样变形时出现明显的晶界应力集中和表面凹凸起伏, 屈服强度明显增加, 为115 MPa, 断后伸长率下降至36%, 具有混合型断口. 连续柱状晶组织CuNi10Fe1Mn合金的晶粒取向和晶界分布的各向异性是造成变形行为各向异性的原因.

In continuous unidirectional solidification process, an unidirectional heat transfer condition can be established to control grain growth direction along the solidification direction (SD). By this method, continuous columnar-grained (CCG) polycrystalline alloys without transverse grain boundary can be obtained, which possess high orientated texture and straight grain boundary morphology. High orientated texture can significantly improve the consistency among the grains, and the straight grain boundaries reduce the number of coordinated strain components, resulting in high plasticity and excellent extension behavior along the SD in the CCG alloys. For example, the CCG polycrystalline CuNi10Fe1Mn alloy has a high tensile elongation (>40%). However, as described above, the CCG polycrystalline alloy has an extremely anisotropic microstructure. In order to improve its performance, select the appropriate processing methods, and establish a reasonable process, its mechanical properties and deformation behavior were investigated with tensile direction along the SD or perpendicular to the solidification direction (PD) in this work. The electron back-scatter diffraction (EBSD) and digital image correlation (DIC) techniques were introduced to study the effects of microstructure anisotropy on the mechanical properties and deformation behavior. The results indicate that both SD and PD samples have [100] preferred orientation. All grains in SD samples (Taylor factor m=2.17) are nearby [100], while some grains in PD samples (Taylor factor m=2.93) scatter among [001]-[011]. Microstructure characteristics of low orientation dispersion and no horizontal grain boundary in SD samples contribute to the uniform stress distribution and consistent deformation behavior in each grain along the tensile direction. The yield strength, tensile strength and elongation are 85 MPa, 215 MPa and 42%, respectively. Compared to SD samples, PD samples appear to grain boundary stress concentration and zigzag surface morphologies due to the orientation dispersion and horizontal grain boundaries. As a result, the yield strength markedly increases to 115 MPa, and the elongation decreases to 36%. The SD and PD samples occur ductile and mixed fracture, respectively. The anisotropic deformation behavior of CCG polycrystalline CuNi10Fe1Mn alloy is attributed to the anisotropic grain orientation and the grain boundary distribution.