高導熱鋁基複合材料(Gr/A356)之擠壓鑄造製程與性質研究

Abstract

本實驗以擠壓鑄造法製作高導熱係數之石墨-鋁基複合材料，將鱗狀石墨與顆粒狀石墨以不同比例均勻混合後置入模具以10MPa的壓力預壓，然後加熱至550℃，隨後將750℃的A356鋁湯以50MPa的壓力擠入。可得石墨均勻散佈且幾無氣孔之石墨-鋁基複合材料以OM，SEM觀察其表面形態與微結構並使用x-光散射儀分析石墨與A356是否產生Al4C3化合物。最後使用TPS2500熱傳導係數儀測量複合材料的熱傳導係數與熱擴散係數。 依實驗結果顯示，若石墨全為顆粒狀石墨，石墨的體積分率僅43％，複合材料的導熱係數為174W/mK，在石墨中加入鱗狀石墨則後，石墨的體積分率可依鱗狀石墨的比例增加至74.6％，而複合材料的導熱係數可達263W/mK 是A356基材128W/mK的兩倍以上。

Manufacturing high thermal conductivity and high volume fraction graphite-reinforced aluminum matrix composite was taken by squeeze casting procedure. Mixing several different ratios of flake graphite and particulate graphite, then those mixtures pour into the mold and pre-pressed with pressure 10MPa.Graphite was heated up to 550℃ and the melting aluminum alloy (A356) with 750℃ was infiltrated into the interconnect pores of graphite by 50MPa pressure. A uniform and nearly pore less graphite-reinforced aluminum matrix composite can be obtained. After the observation of the surface morphology and microstructure via optical microscope (OM) and scanning election microscope (SEM), as well as phase analysis by X-ray diffractometer, there is no A14C3 compound between graphite and aluminums interface. The thermal conductivity and thermal diffusivity were measured by TPS2500 thermal conductivity analyzer. The test result shows that graphite volume fraction is only 43% and thermal conductivity of aluminum composite is about 174W/mK with all graphite particles. Owing to the addition of flake graphite, the volume fraction of graphite can be increased to 74.6%. The thermal conductivity of aluminum composite is raised up to 263W/mK which is 2 times higher than that of A356 (128W/mK).