SiC顆粒參與下快冷鎂合金異質形核與高溫晶粒長大SiC顆粒參與下快冷鎂合金異質形核與高溫晶粒長大Heterogeneous nucleation and grain growth at high temperature for quenched magnesium alloy containing SiC particle 采用銅模噴鑄與高溫退火相結合，研究快冷AZ91+SiC合金組織細化與高溫晶粒長大，揭示SiC顆粒對亞快速凝固鎂合金異質形核及熱穩定性的影響。結果表明：SiC可促進亞快速凝固過程中異質形核，阻礙凝固界面遷移，顯著細化噴鑄合金組織。400 ℃等溫退火后，組織從枝晶向等軸晶轉變并發生明顯晶粒長大，快冷AZ91合金保溫8 h后平均晶粒尺寸達78 μm。添加2%SiC后，晶粒長大得到有效控制，8 h退火處理后平均晶粒尺寸僅為22 μm。SiC的存在提高了基體中晶格畸變，退火組織中析出層片狀與粒狀共存的沉淀相。晶粒細化及SiC的添加提高了快冷鎂合金顯微硬度。隨退火時間延長，合金硬度下降。沉淀相的析出導致AZ91+2%SiC合金硬度增加，最高可達111HV，比AZ91合金的硬度提高63.2%。 Using copper-mould spray casting and annealing techniques, microstructure refinement and grain growth at high temperature for quenched AZ91+SiC alloy were analyzed. Effects of SiC on heterogeneous nucleation of sub-rapid solidified alloy and thermal stability were elucidated. Results show that SiC promotes heterogeneous nucleation and inhibits interface migration. Grain size in spray casted alloy reveals significant reduction. After annealing at 400 ℃, dendrite transits to equiaxed grain, accompanied by obvious grain growth. The grain size of quenched AZ91 alloy after annealing for 8 h is 78 μm, whereas it reduces to 22 μm after adding 2%SiC, indicating the suppression of grain growth. The increase of lattice distortion by SiC generates lamellar and granular precipitations. Grain refinement and SiC increase the micro-hardness of quenched alloy and reduction occurs for longer annealing time. The maximum hardness of 111HV can be obtained in AZ91+2%SiC alloy due to precipitates, which increases by 63.2% than that of AZ91 alloy.
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