(蘭州理工大學(xué) 甘肅省省部共建有色金屬新材料國家重點(diǎn)實(shí)驗(yàn)室,
蘭州 730050)
摘 要: 采用水淬法研究了具有5種不同凝固組織的AZ91D鎂合金半固態(tài)熔化過程的行為。 結(jié)果表明：增加冷卻速率、 預(yù)變形處理和晶粒細(xì)化有利于初始凝固組織中存在的非平衡組織的分散細(xì)化。 原始組織中的非平衡共晶組織在加熱過程中大部分?jǐn)U散溶解而溶入基體中， 剩余部分在加熱過程中首先熔化；冷卻速率越大或預(yù)變形處理以后的試樣在熔化過程中更容易發(fā)生二次枝晶臂之間的合并。 提出半固態(tài)熔化過程可分為成分均勻化、 共晶熔化及部分初生相的熔化和球化完成3個階段， 不同熔化階段的控制性因素不同。 熔化后的半固態(tài)組織中固態(tài)顆粒的尺寸和形貌主要與初始組織的形貌、加熱過程中非平衡組織的溶解速度及加熱速度有關(guān)。
關(guān)鍵字: AZ91D鎂合金；非平衡組織； 熔化； 擴(kuò)散； 半固態(tài)
（State Key Laboratory of Gansu Province Advanced Nonferrous Materials, Lanzhou University of Technology,
Lanzhou 730050, China）
Abstract: The semi-solid melting behavior of AZ91D magnesium alloy with different original microstructures was investigated by quenching method. The results show that, increasing cooling rate, pre-deformation and grain refinement are useful for spreading of the non-equilibrium microstructure around the primary grains. Most of non-equilibrium microstructures in the original microstructure dissolve into the α-Mg matrix due to the diffusion of the solute and then the remainder is melted firstly. The more the increasing of cooling rate or pre-deformation, the more the secondary dendrite arms are easy to coarsen. The partial melting process during increasing temperature includes uniformization of the compositions， divorced eutectic melting， and the partial melting and glomeration of primary α-Mg. A predominant factor is different during different stages. The size and shape of solid phase in semi-solid microstructure are related with the original microstructure, diffusion rate of non-equilibrium microstructure and heating-up rate.
Key words: AZ91D magnesium alloy; non-equilibrium microstructure; melting; diffusion; semi-solid state
