搅拌铸造法制备短碳纤维/AZ91复合材料的组织与性能

采用搅拌铸造法制备了不同体积分数（10vol%、15vol%、20vol%）的短碳纤维增强镁基（CF_s/AZ91）复合材料，并选取了三个挤压比和两个挤压温度对其进行热挤压变形，采用光学显微镜（OM）、SEM和TEM对CF_s/AZ91复合材料的显微组织进行了观察，并测试其室温力学性能及阻尼性能。研究结果表明，热挤压能够有效降低CF_s/AZ91复合材料气孔率；在热挤压过程中，纤维沿挤压方向定向排列，同时基体发生动态再结晶。随着挤压温度及挤压比的增大，晶粒呈现等轴状，组织更加均匀。CF_s/AZ91复合材料经过挤压后，其力学性能得到提高，屈服强度和抗拉强度随挤压比和CF_s体积分数的增大而增大，然而CF_s纤维在热挤压后发生明显断裂，限制了挤压态复合材料强度的进一步提升。低温低挤压比条件下，CF_s/AZ91复合材料具有较好的阻尼性能，随着挤压比及挤压温度的升高，CF_s/AZ91复合材料室温及高温阻尼性能均有所降低。

Microstructure and mechanical properties of short carbon fiber/AZ91 composite fabricated by stir-casting

The short carbon fiber (CF_s) reinforced AZ91 Mg matrix composites with different CF_s volume fractions (10vol%, 15vol%, 20vol%) were fabricated by stir-casting method. The cast CF_s/AZ91 composites were extruded into bars with three different extrusion ratios at 250℃ and 350℃, respectively. During the hot extrusion, grains of the AZ91 matrix are refined due to the dynamic recrystallizaiton while the CF_s distribute parallel to the extrusion direction. With increasing of the extrusion temperature and extrusion ratio, the porosity ratio of the CF_s/AZ91 composites is reduced effectively and the recrystalled grains grow up accompanied by the improvement of the microstructure homogeneity. The tensile properties of CF_s/AZ91 composites are improved due to the improved microstructure whereas the fiber fractures obviously during extrusion, which will restrict the further improvement of the mechanical properties. The CF_s/AZ91 composite extruded with small extrusion ratio at lower temperature has better damping capabilities than those of the composites extruded with high extrusion ratio and higher temperature.