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28卷    第2期    总第227期    2018年2月

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文章编号:1004-0609(2018)-02-0223-10
AZ61镁合金降温多向压缩中的动态析出及其对晶粒细化和力学性能的影响
方正午1,肖振宇1,张笃秀1,尹 勇1,杨续跃1, 2, 3

(1. 中南大学 材料科学与工程学院,长沙 410083; 2. 中南大学 有色金属先进结构材料与制造协同创新中心,长沙 410083; 3. 中南大学 有色金属学材料科学与工程教育部重点实验室,长沙 410083)

摘 要: 对AZ61镁合金进行降温多向压缩变形,利用OM,SEM/EBSD及TEM技术对其晶粒细化和析出相变化进行了观察和分析。结果表明:在623~483 K温度范围内降温多向压缩时AZ61镁合金晶粒急剧细化,低角晶界通过吸收位错转变成高角晶界,而降温变形会明显抑制晶粒长大和晶界高角化,5道次变形后还存在大量中低角晶界,平均晶粒尺寸约为0.8 μm。变形初期析出的第二相尺寸较大,随着变形道次的增加,第二相细化的同时数量明显增多。降温变形可促进动态析出,使得析出相分布更加细小、弥散。动态析出使得AZ61相对AZ31镁合金具有更高的硬度。AZ61镁合金经降温变形后强度和延性得到同步提升,尤其是5道次变形后伸长率显著提高,这是细小第二相在中低角晶界上动态析出造成的。

 

关键字: 镁合金;多向压缩;中低角度晶界;动态析出

Dynamic precipitation and its effect on grain refinement and mechanical properties in AZ61 Mg alloy during multi-directional forging under decreasing temperature conditions
FANG Zheng-wu1, XIAO Zhen-yu1, ZHANG Du-xiu1, YING Yong1, YANG Xu-yue1, 2, 3

1. School of Materials Science and Engineering, Central South University, Changsha 410083, China; 2. Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083, China; 3. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China

Abstract:Dynamic precipitation and its effect on grain refinement and mechanical properties of AZ61 Mg alloy during multi-directional forging in temperature range from 623 K to 483 K were investigated by OM, SEM/EBSD and TEM techniques. Dynamic precipitation of Mg17Al12 phase does happen at the early stage of multi-directional forging and grain size is significantly refined to 0.8 μm after five passes deformation. The initial size of precipitates is relatively big, and then precipitates become dispersed and are refined to nanometer scale. The nanometer dispersed precipitation retards the dislocation movement, along with the temperature decreasing, resulting in the high density of dislocations and low medium angle grain boundaries inside the grain. The strength and ductility of AZ61 Mg alloy are simultaneously improved after multi-directional forging under decreasing temperature. The dramatic improvement of ductility is found after the whole five passes deformation finished, which can be attributed to the dynamic precipitation occurring on the low or medium angle grain boundary.

 

Key words: magnesium alloy; multi-directional forging; low-medium angle grain boundary; dynamic precipitation

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

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

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