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0.8μm。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。
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 Mg17 Al12 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.
出处
《中国有色金属学报》
EI
CAS
CSCD
北大核心
2018年第2期223-232,共10页
The Chinese Journal of Nonferrous Metals
基金
国家自然科学基金资助项目(51474241
51771230)
国家重点基础研究发展计划资助项目(2013CB632204)
湖南省重点研发项目(2016WK2018)~~
关键词
镁合金
多向压缩
中低角度晶界
动态析出
magnesium alloy
multi-directional forging
low-medium angle grain boundary
dynamic precipitation
