(1. 蘭州理工大學(xué) 省部共建有色金屬先進(jìn)加工與再利用國家重點(diǎn)實(shí)驗(yàn)室，蘭州 730050；
2. 蘭州理工大學(xué) 有色金屬合金及加工教育部重點(diǎn)實(shí)驗(yàn)室，蘭州 730050)
摘 要: 利用等溫?zé)崽幚矸ㄑ芯刻剿髁薓g-7Zn-1Cu-0.1Mn-0.1Cr合金半固態(tài)組織演變，并分析非枝晶顆粒的形成機(jī)理。從保溫時(shí)間和保溫溫度兩個(gè)角度對(duì)合金的組織演變進(jìn)行研究。結(jié)果表明：Mg-7Zn-1Cu-0.1Mn- 0.1Cr合金鑄態(tài)枝晶組織可以轉(zhuǎn)變?yōu)榘牍虘B(tài)非枝晶組織，獲得球狀顆粒相。在580 ℃保溫30 min時(shí)可以獲得較優(yōu)良的半固態(tài)組織，其固相率、形狀因子和顆粒平均尺寸分別為65% 、1.37及45 μm。增加等溫溫度或延長保溫時(shí)間均使得半固態(tài)組織顆粒平均尺寸和形狀因子先減小后增大，固相率則一直下降。合金在重熔過程中發(fā)生相的轉(zhuǎn)變，主要有枝晶快速粗化合并、組織分離、球化，晶粒合并粗化等狀態(tài)。亞晶界提供溶質(zhì)原子擴(kuò)散通道，枝晶根部優(yōu)先熔斷，從而促進(jìn)組織分離，晶粒表面曲率不同使得晶粒球化，合并粗化階段主要機(jī)制為合并長大以及Ostwald熟化。
關(guān)鍵字: 鎂合金；半固態(tài)；等溫?zé)崽幚恚唤M織演變
（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 isothermal heat treatment method was used to explore the evolution of semi-solid microstructure of Mg-7Zn-1Cu-0.1Mn-0.1Cr alloy and analyze the formation mechanism of non-dendritic particles. The microstructure evolution of the alloy was studied from the perspective of holding time and holding temperature. The results show that the as-cast dendrite structure of Mg-7Zn-1Cu-0.1Mn-0.1Cr alloy can be transformed into a semi-solid non-dendritic structure to obtain a spherical particle phase. A good semi-solid structure can be obtained when the alloy was kept at 580 ℃ for 30 min. Its solid phase ratio, shape factor and average particle size are 65%, 1.37 and 45 μm, respectively. Increasing the isothermal temperature or prolonging the holding time makes the average size and shape factor of the semi-solid tissue particles decrease first and then increase, and the solid phase rate decreases. The phase transformation of the alloy during the remelting process mainly includes rapid dendrite coarsening and merging, structure separation, spheroidization, and grain merging and coarsening. The subgrain boundary provides a solute atom diffusion channel, and preferential fusing at the root of the dendrite promotes the separation of the structure. The different curvature of the grain surface makes the grain spheroidize. The main mechanism of the merger roughening stage is merger growth and Ostwald ripening.
Key words: magnesium alloy; semi-solid; isothermal heat treatment; microstructure evolution
