热压法制备高含量B_4C/铝基复合材料的显微结构与力学性能

Microstructure and mechanical properties of high content B_4C-aluminium composites fabricated by hot-pressing sintering

采用低温真空热压法制备B4C质量分数为30%、平均粒度为23μm的B4C/Al基复合材料,热压温度控制在基体6061Al合金的固液相线之间。对B4C/Al复合材料进行显微结构分析和力学性能检测,结果表明:B4C/Al复合材料内无大尺寸的显微缺陷,组织分布较均匀、致密,界面结合较好;B4C/Al基复合材料的硬度比基体6061铝合金提高34.9%,断裂韧性是B4C增强颗粒断裂韧性的5.16倍,屈服强度比基体提高198.3%。利用Ramakrishnan提出的金属基复合材料屈服强度的分析模型,对30%B4C/Al复合材料的屈服强度进行计算,计算结果与实验结果基本符合。分析表明微米级B4C颗粒对6061Al合金的增强机制主要为载荷增强和位错增强。

30%B4C （mass fraction） particle-reinforcing Al matrix composite with the average particle size 23μm of was prepared by low temperature vacuum hot-pressing technique. The preparation temperature was between the solid and liquid phase line of the 6061Al matrix. The microstructure and mechanical property were analyzed. The results show that the particles are uniformly distributed in the B4C/Al composite without agglomeration and there is mutual diffusion between the particles and matrix. The interface bonds between matrix and reinforcer well. The hardness of B4C/Al composite is 34.9%higher than that of 6061 aluminum alloy. The fracture toughness of B4C/Al composite is 5.16 times larger than that of the B4C material and the yield strength increases 198.3%than that of the matrix. An analytical model for the strength of metal matrix composites presented by Ramakrishnan was selected to calculate the yield strength of the 30%B4C/Al composite. The results of theoretical calculations agree well with the experimental data. The strengthening mechanisms of B4C particle-reinforcing Al matrix composite with micron particle size are mainly loading strengthening and dislocation strengthening.