(南昌航空大學(xué) 輕合金加工科學(xué)與技術(shù)國防重點(diǎn)學(xué)科實(shí)驗(yàn)室，南昌 330063)
摘 要: 采用銅模噴鑄和單輥甩帶分別制備AZ91D鎂合金非平衡凝固試樣，利用ProCAST數(shù)值模擬軟件及理論公式分別估算相應(yīng)冷卻速率。綜合采用光學(xué)顯微鏡、掃描電鏡、能譜分析儀、X射線衍射儀及差熱分析儀對比研究冷卻速率對鎂合金非平衡凝固組織的影響規(guī)律。結(jié)果表明：隨冷卻速率提高，AZ91D合金的初生相形貌從粗大枝晶向細(xì)小等軸晶發(fā)生轉(zhuǎn)變，晶粒發(fā)生明顯細(xì)化，平均尺寸從鑄態(tài)條件下的800 μm降低到單輥甩帶條件下的5 μm以內(nèi)。共晶相從連續(xù)網(wǎng)狀向不連續(xù)彌散狀分布轉(zhuǎn)變，體積分?jǐn)?shù)不斷減小，單輥甩帶條件下可制備出單相固溶體組織。快速凝固條件下合金基體中Mg和Al元素成分分布均勻，溶質(zhì)偏析得到有效控制。
關(guān)鍵字: 鎂合金；非平衡凝固；晶粒細(xì)化；溶質(zhì)偏析
（National Defence Key Discipline Laboratory of Light Alloy Processing Science and Technology,
Nanchang Hangkong University, Nanchang 330063, China）
Abstract:Non-equilibrium solidified specimens of AZ91D magnesium alloy were fabricated by copper mould casting and melt-spinning techniques, separately. The corresponding cooling rates were calculated by numerical simulation ProCAST software and theoretical equation. Using optical microscopy, scanning electron microscopy, energy dispersive spectrum, X-ray diffractometry and differential thermal analyzer, the effects of the cooling rate on the non-equilibrium solidified microstructures were investigated. The results show that the morphology of primary phase changes from coarse dendrite to fine equiaxed grain with increasing cooling rate, as indicated by the significant reduction of grain size from 800 μm under as-cast condition to within 5 μm for rapid solidification. Moreover, the distribution of eutectic phase varies from continuous network to discontinuous dispersion and its volume fraction decreases gradually. Single-phase solid solution structure can be fabricated by melt-spinning method. Both the distribution of Mg and Al elements in rapid solidified alloy are homogeneous without the occurrence of solute segregation.
Key words: magnesium alloy; non-equilibrium solidification; grain refinement; solute segregation
