Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报

ZHONGGUO YOUSEJINSHU XUEBAO

第31卷    第6期    总第267期    2021年6月

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文章编号:1004-0609(2021)-06-1452-11
Mg-7Zn-1Cu-0.1Mn-0.1Cr合金半固态组织演变
黄晓锋1, 2,尚文涛1,杨剑桥1,魏浪浪1,杨 凡1,张展裕1,张 胜1

(1. 兰州理工大学 省部共建有色金属先进加工与再利用国家重点实验室,兰州 730050;
2. 兰州理工大学 有色金属合金及加工教育部重点实验室,兰州 730050
)

摘 要: 利用等温热处理法研究探索了Mg-7Zn-1Cu-0.1Mn-0.1Cr合金半固态组织演变,并分析非枝晶颗粒的形成机理。从保温时间和保温温度两个角度对合金的组织演变进行研究。结果表明:Mg-7Zn-1Cu-0.1Mn- 0.1Cr合金铸态枝晶组织可以转变为半固态非枝晶组织,获得球状颗粒相。在580 ℃保温30 min时可以获得较优良的半固态组织,其固相率、形状因子和颗粒平均尺寸分别为65% 、1.37及45 μm。增加等温温度或延长保温时间均使得半固态组织颗粒平均尺寸和形状因子先减小后增大,固相率则一直下降。合金在重熔过程中发生相的转变,主要有枝晶快速粗化合并、组织分离、球化,晶粒合并粗化等状态。亚晶界提供溶质原子扩散通道,枝晶根部优先熔断,从而促进组织分离,晶粒表面曲率不同使得晶粒球化,合并粗化阶段主要机制为合并长大以及Ostwald熟化。

 

关键字: 镁合金;半固态;等温热处理;组织演变

Semi-solid microstructure evolution of Mg-7Zn-1Cu-0.1Mn-0.1Cr alloy
HUANG Xiao-feng1, 2, SHANG Wen-tao1, YANG Jian-qiao1, WEI Lang-lang1, YANG Fan1, ZHANG Zhan-yu1, ZHANG Sheng1

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

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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