(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: 采用等溫熱處理工藝研究了保溫溫度以及保溫時間對ADC2-0.4Mg-0.9Cu合金半固態(tài)組織演變的影響。結(jié)果表明：等溫熱處理使得鑄態(tài)合金中的不規(guī)則樹枝晶組織轉(zhuǎn)變?yōu)榍驙罨蚪驙畹姆侵ЫM織。適當?shù)靥岣弑販囟然蜓娱L保溫時間有利于ADC2-0.4Mg-0.9Cu合金非枝晶組織的分離與球化，但保溫溫度超過610 ℃或在較高溫度下保溫時間超過15 min后，非枝晶組織易發(fā)生粗化，這種現(xiàn)象是由合并長大機制和Ostwald熟化機制共同作用導致的。ADC2-0.4Mg-0.9Cu合金整個半固態(tài)組織演變過程中，經(jīng)歷了枝晶粗化、分離與球化以及熟化粗化三個階段；最佳等溫熱處理工藝為：610 ℃保溫15 min，此時非枝晶平均晶粒尺寸、固相率和形狀因子分別為50.162 μm、42.75%和1.671。
關(guān)鍵字: ADC2-0.4Mg-0.9Cu合金；非枝晶態(tài)組織；等溫熱處理；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 Nonferrous Metal Alloys and Processing, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China）
Abstract:The effects of secondary heating temperature and holding time on microstructure evolution of semi-solid ADC2-0.4Mg-0.9Cu aluminum alloy were studied by using semi-solid isothermal heat treatment process. The results show that the amorphous dendritic structure of the alloy transforms into spherical and near-spherical non-dendritic structure by isothermal heat treatment. It is beneficial to increase the holding temperature or prolong the holding time properly for the separation and spheroidization of ADC2-0.4Mg-0.9Cu alloy. However, when the holding temperature exceeds 610 ℃ or the holding time exceeds 15 min, the non-dendritic tissues are prone to coarsening, which is caused by the combined growth mechanism and Ostwald maturation mechanism. The semi-solid microstructure evolution of ADC2-0.4Mg-0.9Cu aluminum alloy undergoes three processes: dendrite coarsening, separation, spheroidization and finally ripening coarsening. The average grain size, solid fraction and shape factor of non-dendrites are 50.162 μm, 42.75% and 1.671, respectively, under the optimal isothermal treatment at 610 ℃ for 15 min.
Key words: ADC2-0.4Mg-0.9Cu aluminum alloy; nondendritic structure; isothermal heat treatment; evolution mechanism
