(南昌航空大學(xué) 輕合金加工科學(xué)與技術(shù)國(guó)防重點(diǎn)學(xué)科實(shí)驗(yàn)室，南昌 330063)
摘 要: 采用銅模噴鑄與等溫?zé)崽幚硐嘟Y(jié)合，制備出納米SiC參與下快冷鎂合金細(xì)晶組織，研究熱處理溫度對(duì)非平衡凝固鎂合金固溶組織轉(zhuǎn)變的影響及其高溫晶粒長(zhǎng)大行為。結(jié)果表明：提高冷速與添加納米SiC可實(shí)現(xiàn)鎂合金的復(fù)合細(xì)化，有利于形成細(xì)小花瓣?duì)罱M織。經(jīng)320、370和400 ℃等溫處理2 h后，快冷AZ91+2%納米SiC合金從不完全固溶向完全固溶發(fā)生轉(zhuǎn)變，溶質(zhì)偏析程度降低，同時(shí)，晶界β-Mg17Al12相不斷消失，最終獲得多邊形等軸晶組織。由于納米SiC對(duì)晶界遷移起到良好的抑制作用，亞穩(wěn)細(xì)晶組織的高溫晶粒長(zhǎng)大行為得到有效控制，其中經(jīng)400 ℃固溶8 h后的平均晶粒尺寸僅為13 μm，快冷合金的熱穩(wěn)定性得到顯著提高。
關(guān)鍵字: 鎂合金；非平衡凝固；固溶處理；組織細(xì)化；晶粒長(zhǎng)大
（National Defence Key Discipline Laboratory of Light Alloy Processing Science and Technology, Nanchang Hangkong University, Nanchang 330063, China）
Abstract:With the combination of copper mould spray casting and isothermal heat treatment, rapidly cooled magnesium alloy with fine grain microstructure was prepared by adding nano SiC. The effects of annealing temperature on solid solution transition and high temperature grain growth behavior were elucidated. The results show that both the increase of cooling rate and the addition of SiC promote duplex refinement of magnesium alloy, which is beneficial to the formation of fine petal-like structure. After isothermal treatment at 320, 370 and 400 ℃ for 2 h, a transition from insufficient solid solution to complete solid solution occurs, accompanied by the reduction of solute segregation. The disappearance of β-Mg17Al12 in grain boundary generates the formation of polygon equiaxed grain structure. Due to the excellent inhibition effect of nano SiC on grain boundary migration, the grain growth at high temperature is effectively suppressed. The average grain size of rapidly cooled alloy after solid solution at 400 ℃ for 8 h is merely 13 μm, and the thermal stability of fine grain microstructure is greatly improved.
Key words: magnesium alloy; non-equilibrium solidification; solid solution treatment; microstructure refinement; grain growth
