热反挤压变形对n-SiC_p/2024复合材料组织与性能的影响

Effect of Hot Backward Extrusion on Microstructure and Properties of n-SiC_p/2024 Composites

利用半连续铸造-热反挤压工艺制备了n-SiCp/2024复合材料棒材。通过金相组织观察(OM)、扫描电镜(SEM)、室温力学性能以及电导率测试等手段,研究了该复合材料在热反挤压前后的显微组织、力学性能与电导率的变化情况。结果表明:复合材料铸锭中粗大第二相沿晶界非连续分布,Cu、Mg元素偏聚显著,大多数n-SiCP偏聚在晶界处,少量分布在晶内;热挤压变形后,n-SiCp团聚现象显著消除,Cu、Mg元素及n-SiCP分布趋于均匀,n-SiCp及破碎第二相沿热挤压方向呈纤维状分布;拉伸实验结果表明,热挤压后复合材料的强度及塑性显著提高;热挤压后,复合材料的电导率低于基体合金。

The n-SiCp/2024 composites hot extruded bars were prepared by semi-continuous casting and hot backward extrusion process. The microstructure, mechanical properties and conductivity of the n-SiCp/2024 composite before and after hot backward extrusion were investigated by optical microscope （OM）, scanning electron microscope （SEM）, tensile and conductivity test. The results showed that the as-cast composite was composed of phases which were on the grain boundary in large size and in discontinuity, Cu and Mg elements were segregated significantly, most of the n-SiCp located in the inter-granular regions, only few n-SiCp distributed within the a-Al grain. The n-SiCp clus- tering were largely eliminated after hot extrusion, distribution o{ Cu, Mg elements and n-SiCp associating with a uniform trendy, n-SiC, and the secondary phases distributed along the direction of the metal plastic flowing. Tensile test indicated that the strength and ductility of n-SiCp/2024 composite increased obviously after hot extrusion process, meanwhile, conductivity of the n-SiCp/2024 composite was lower than the matrix alloy.