高导热鳞片石墨/2024Al组织与性能研究

Microstructure and Properties of High Thermal Conductivity Graphite Flake/2024 Aluminum

以2024铝合金为基体、平均粒径100μm的高导热鳞片石墨为增强体,并对鳞片石墨表面镀钛,通过放电等离子烧结(spark plasma sintering, SPS),制备石墨体积分数为60%的高导热鳞片石墨/2024Al复合材料。烧结温度是540℃,烧结压力是50 MPa,烧结时间5 min。通过金相显微镜(OM)、 X射线衍射仪(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对未镀钛和镀钛鳞片石墨/2024Al复合材料的显微组织和成分进行了分析和表征,结果显示,复合材料中都没有有害相Al4C3的生成,镀钛鳞片石墨/2024Al复合材料具有更好的界面结合。测试其热导率、热膨胀系数以及抗弯强度,未镀钛和镀钛鳞片石墨/2024Al复合材料在沿鳞片石墨片层方向的热导率分别为398和368 W·m-1·K-1,变化不大;垂直于鳞片石墨片层方向的热导率分别为35和56 W·m-1·K-1,有较大提高。镀钛后,复合材料的热膨胀系数降低,抗弯强度为96 MPa,和未镀钛鳞片石墨/2024Al的抗弯强度37 MPa相比,有较大提高。对鳞片石墨表面镀钛,能够改善碳与铝的界面结合,提高鳞片石墨/2024Al复合材料的热物理与力学性能。

The high thermal conductivity graphite flake/2024 aluminum composites was prepared by spark plasma sintering(SPS)with 2024 aluminum alloy as substrate and high thermal conductivity graphite flake as reinforcement,with sintering temperature of 540℃,sintering pressure of 50 MPa,and sintering time of 5 min.The microstructures and compositions of non-titanium and titanium-coated graphite flake/2024 Al composites were investigated by optical microscope(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results showed that there was no harmful phase of Al4C3 in the composites,and the Ti-coated graphite flake/2024 Al composite had better interface.The thermal conductivity,thermal expansion coefficient and bending strength were tested.The thermal conductivity of non-titanium-coated and titanium-coated graphite flake/2024 Al composites in the direction of graphite flake sheet was 398 and 368 W·m-1·K-1,respectively.The thermal conductivity in the direction perpendicular to the flake graphite sheet was 35 and 56 W·m-1·K-1,which was greatly improved.After the titanium coating,the thermal expansion coefficient of the composite material was reduced and the bending strength was 96 MPa,which was greatly improved compared with the bending strength of the non-titanium scale graphite flake/2024 Al composite which was 37 MPa.Titanium coating on the surface of graphite flake could improve the interface between carbon and aluminum and improve the thermal and mechanical properties of graphite flake/2024 Al composites.