Microstructure And Mechanical Properties Of Al-Si Alloy Reinforced By Al ₆₃ Cu₂₅ Fe₁₂ Quasicrystal

The Al₆₃Cu₂₅Fe₁₂ quisicrystal alloy was manufactured under conventional casting condition and fast cooling method. The Al₆₃Cu₂₅Fe₁₂ quisicrystal alloy of cast and fast cooling state were studied using scanning electron microscopy(SEM), X-ray diffraction and Differential scanning calorimetry(DSC). The single phase composing Al₆₃Cu₂₅Fe₁₂ quisicrystal cast was prepared by heat treatment. The Al₆₃Cu₂₅Fe₁₂ quasicrystal alloy after heat treatment was broken into certain size particles. The different amount quasicrystal alloy particles were added into Al-7%Si and Al-12.6%Si alloy and Strengthening treat the substract alloy. Time to study through different insulation in the matrix alloy The changes of quasicrystalline phase in the substract alloy was studied with different holing time. The effect of the amount of the quasicrystal particles on structure and mechanism properties was analysed.It is noticed that the conventional casting Al₆₃Cu₂₅Fe₁₂ alloy in Electric Arc Furnace is multi-phase structure. It is composed of I,λ,βandÏ„. The order of generation isλ,β, I quasicrystalline phase andÏ„in the process of the cooling solidification. Phase transition temperature of theÏ„, I,βandλwere 692℃, 880℃, 996℃and 1117℃, respectively, which was established by DSC. It was found that the fast-cooling Al₆₃Cu₂₅Fe₁₂ alloy mainly was composed of the large number of quasicrystal I phase and a small amount ofÏ„phase. Furthermore, the phase constitutes was quite different matching to the diverse cooling rates and the two quasi-phase formation mechanism were analyzed in the solidification proces. Almost single i-phase constitute can be obtained after heat treatment at 750℃for 3h and quenching in the protection of argon.Cast Al₆₃Cu₂₅Fe₁₂ quasicrystal alloy after the heat treatment was broken into a certain size particles and pressed into blocks with the same quality of Al powder, The particles were put into Al-7% Si alloys at 700℃after 3 minutes with the method of mechanical rabble and casting. With the addition of quasicrystalline particles increases, the quasicrystalline particles increased significantly, and evenly distributed along the grain boundaries, it was no obvious agglomeration and the particle size has been significantly reduced. when the holding time was increased, the quasicrystal particles were unstable and gradually melt, there was thermal cracking in Grains, leading to internal defect, and the generation of low-temperature phaseÏ„. With the further increased of the holding time, quasi-crystalline particles were completely dissolved, the elements of quasicrystalline phase were diffused into the matrix alloy and a number of compounds which was scattered distribution in the matrix alloy were formed. Mechanical test results show that with the quasicrystalline particles increasing in Al-7%Si, the hardness and tensile strength increased, while the elongation was unchanged first and then decreased. When the addition amount of Al₆₃Cu₂₅Fe₁₂ quasicrystal is 6%, the elongation had the largest value.Al₆₃Cu₂₅Fe₁₂ quasicrystalline particles were added into the Al-12.6% Si alloy with the same method. Al-12.6% Si alloy reinforced by quasicrystal mainly was composed of the eutectic Si and the gray quasicrystalline particles. And compared with Al-12.6% Si alloy, eutectic Si has been significantly refined. When the amount of quasicrystals was less, the quasicrystal particles and the eutectic Si were dispersed in the matrix alloy. With the amount of the quasicrystal was increased, the quasicrystal particle were agglomeration. when the holding time was increased, the quasicrystal particles were unstable and gradually melt, there was thermal cracking in grains, leading to internal defect, but there was noÏ„phase. With the further increased of the holding time, quasi-crystalline particles were completely dissolved, the elements of quasicrystalline phase were diffused into the matrix alloy and a number of compounds which was scattered distribution in the matrix alloy were formed. Mechanical test results show that with the Al₆₃Cu₂₅Fe₁₂ quasicrystalline particles increasing, the hardness of the Al-12.6%Si reinforced by Al₆₃Cu₂₅Fe₁₂ quasicrystalline increased, while the elongation was unchanged first and then decreased . The tensile strength was increased first and then decreased. When the addition amount of Al₆₃Cu₂₅Fe₁₂ quasicrystal is 3% and 6%, the elongation and the tensile strength had the largest value, respectively. The 3% (Al₆₃Cu₂₅Fe₁₂)p/ Al-12.6% Si alloy and Al-12.6% Si alloy were solution treated and quenched ,and then artificial aging at 185℃for 24 hours , there were aging peaks. And the aging peak of the 3% (Al₆₃Cu₂₅Fe₁₂)p/ Al-12.6% Si alloy is early appearanced.