(1. 蘭州理工大學 省部共建有色金屬先進加工與再利用國家重點實驗室，蘭州 730050；
2. 蘭州理工大學 有色金屬合金及加工教育部重點實驗室，蘭州 730050)
摘 要: 本文研究了Cu含量、重熔溫度及等溫時間對Mg-7Zn-0.3Mn鎂合金半固態(tài)組織演變的影響。結(jié)果表明：Mg-7Zn-0.3Mn-1Cu合金的鑄態(tài)組織由白色α-Mg基體和黑色共晶組織(α-Mg+Mg4Zn7+ MgZn2+CuMnZn)組成。在等溫熱處理過程中，Cu有加速非枝晶顆粒分離和球化的作用，且Cu含量(質(zhì)量分數(shù))為1.0%時效果最佳；Mg-7Zn-0.3Mn-1Cu鎂合金通過適當提高保溫溫度或延長保溫時間，能夠得到細小且分布均勻的球狀顆粒。然而當保溫溫度超過585 ℃或保溫時間超過20 min時，半固態(tài)顆粒則會粗化長大。這種粗化長大現(xiàn)象是在合并長大機制與Ostwald熟化機制共同作用下產(chǎn)生的。在整個等溫熱處理過程中，半固態(tài)組織演變主要經(jīng)歷了初始粗化、組織分離、球化和最后粗化四個階段。Mg-7Zn-0.3Mn-1Cu鎂合金的最佳等溫熱處理工藝參數(shù)為保溫溫度585 ℃和保溫時間20 min，其非枝晶顆粒的平均尺寸、形狀因子和固相率分別為38.85 μm、1.39和53.38%。
關(guān)鍵字: Mg-7Zn-0.3Mn-1Cu鎂合金；Cu含量；非枝晶組織；演變機理
（1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China;
2. Key Laboratory of Non-ferrous Metal Alloys and Processing, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China）
Abstract:The effects of Cu content (0%, 0.5%, 1.0%, 1.5%), remelting temperature and holding time on the evolution of semi-solid non-dendrites of Mg-7Zn-0.3Mn magnesium alloy were studied. The results show that the cast microstructure of the Mg-7Zn-0.3Mn-1Cu alloy is composed of white α-Mg matrix and black eutectic phase (α-Mg+Mg4Zn7+ MgZn2+CuMnZn). And Cu accelerated the separation and spheroidization of non-dendritic particles during isothermal heat treatment, and the effect is optimal when the Cu content (mass fraction) is 1.0%. By properly raising the holding temperature or extending the holding time, Mg-7Zn-0.3Mn-1Cu can obtain finer and more uniform spherical particles. However, when the holding temperature exceeds 585 ℃ or the holding time exceeds 20 min, semi-solid particles will gradually coarsene. This coarsening growth phenomenon is generated by the combined growth mechanism and Ostwald maturation mechanism. During the whole isothermal heat treatment process, the semi-solid microstructure evolution mainly experiences four stages: initial coarsening, tissue separation, spheroidization and final coarsening. The best parameters of isothermal heat treatment of Mg-7Zn-0.3Mn-1Cu are 585 ℃ in holding temperature, 20 min in holding time, and the average particle size, shape factor and solid fraction are 38.85 μm, 1.39 and 53.38%, respectively.
Key words: Mg-7Zn-0.3Mn-1Cu magnesium alloy; Cu content; non-dendritic microstructure; evolution mechanism
