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23卷    第11期    总第176期    2013年11月

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文章编号:1004-0609(2013)11-3039-09
Al含量对Mg-7Zn合金非枝晶组织的影响
冯 凯,黄晓锋,马 颖,吕 峥,李兴鹏,郝 远

(兰州理工大学 甘肃省有色金属新材料省部共建国家重点实验室,兰州 730050)

摘 要: 采用等温热处理法研究Al含量对Mg-7Zn合金半固态组织的影响。结果表明:添加Al元素后,合金的固相率随温度变化曲线逐渐下移。在相同的等温处理工艺下(580 ℃保温30 min),随着Al含量的增加,合金的固相颗粒尺寸逐渐减小,圆整度显著提高,同时固相率明显降低。非枝晶组织主要包括球状及类似球状的初生固相颗粒α1-Mg,水淬二次凝固形成细小的等轴晶α2-Mg以及晶界处和包裹在初生颗粒间的共晶组织。随保温时间的延长,Mg-7Zn-xAl合金非枝晶组织中的初生固相颗粒的尺寸逐渐增加,形状因子逐渐降低,而在后期处于固液平衡阶段,固相率的变化不明显;同时,固相颗粒粗化符合Ostwald熟化机制,且Al元素的加入减小了初生固相颗粒的粗化速率,从而在较宽的保温时间范围内可获得细小圆整的固相颗粒。

 

关键词: Al含量;Mg-Zn-Al合金;半固态;粗化

Effect of Al content on non-dendritic microstructure of Mg-7Zn magnesium alloy
FENG Kai, HUANG Xiao-feng, MA Ying, Lü Zheng, LI Xing-peng, HAO Yuan

State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials,
Lanzhou University of Technology, Lanzhou 730050, China

Abstract:The effect of Al addition on semi-solid microstructures of Mg-7Zn alloy was investigated by isothermal heat-treatment. The results indicate that the solid fractions of alloys are declined by elevated temperature when adding Al into Mg-7Zn alloy. With Al content increasing, the equivalent particle size gradually decreases, the roundness significantly increases and the solid fraction decreases at the same isothermal treatment process (580 ℃, 30 min). The non-dendritic microstructures are composed mainly of globular and similar globular primary particles α1-Mg, the finer equiaxial α2-Mg which forms from quench in water, and the eutectic distributes on the grain-boundary and within the primary solid particles. With holding time increasing, the size of primary solid particles of non-dendritic microstracture of Mg-7Zn-xAl alloy gradually increases and the shape factor decreases, which has no visible effect on the solid fraction of alloys at the solid-liquid equilibrium stage. Simultaneously, the parimary particle size coarsening with holding time obeys the Ostwald ripening mechanism, and adding Al element into Mg-7Zn alloy results in a decrease of coarsening rate of solid particles in semi-solid slurry, consequently, it can obtain the perfect semi-solid microstructure on the wide range of holding time.

 

Key words: Al content; Mg-Zn-Al alloy; semi-solid; coarsening

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

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

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