热处理对金刚石/2024Al复合材料微观组织和热物理性能的影响

采用挤压铸造法制备粒径为5μm、体积分数为50%的金刚石/2024Al 复合材料。退火处理后对其金相组织界面反应、界面结合情况以及金刚石颗粒的内部缺陷进行观察与分析，并对其热物理性能进行测试与研究。结果表明，金刚石/2024Al 复合材料的组织致密，无明显的气孔、夹杂等缺陷；颗粒为不规则多边形，有棱角，分布比较均匀。透射电镜观察表明，部分金刚石颗粒内部有位错和层错存在，而2024Al 基体中的位错密度较大，金刚石/2024Al界面处有较多的界面反应物生成，可能为Al2Cu。复合材料在20~100°C温度区间内的平均热膨胀系数为8.5×10-6°C-1，退火处理的复合材料其热膨胀系数有一定程度的降低；随着温度的升高，复合材料的平均热膨胀系数也呈现增加的趋势。复合材料的热导率约为100 W/（m·K），退火处理能够提高复合材料的热导率。

Effect of heat treatment on microstructure and thermophysical properties of diamond/2024 Al composites

50%diamond particle （5μm） reinforced 2024 aluminum matrix （diamond/2024 Al） composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, and no apparent porosities or significant casting defects were observed in the composites. The diamond-Al interfaces of as-cast and annealed diamond/2024 Al composites were clean, smooth and free from interfacial reaction product. However, a large number of Al2Cu precipitates were found at diamond-Al interface after aging treatment. Moreover, needle-shaped Al2MgCu precipitates in Al matrix were observed after aging treatment. The coefficient of thermal expansion （CTE） of diamond/2024 Al composites was about 8.5×10-6 °C-1 between 20 and 100 °C, which was compatible with that with chip materials. Annealing treatment showed little effect on thermal expansion behavior, and aging treatment could further decrease the CTE of the composites. The thermal conductivity of obtained diamond/2024 Al composites was about 100 W/（m？K）, and it was slightly increased after annealing while decreased after aging treatment.