摘要
对Mg-6Zn-1Gd合金搅拌摩擦焊接头进行固溶处理,采用金相显微镜(OM)、扫描电镜(SEM)、能谱仪(EDS)以及显微硬度测试和室温拉伸试验研究了固溶处理对接头组织和性能的影响。结果表明,在430℃进行固溶处理时,焊核区平均晶粒尺寸随着固溶时间的延长而逐渐增大;当固溶时间超过2 h后,其晶粒尺寸长大更为显著,4 h时达到46μm,约为未固溶接头的3.5倍。焊核区的第二相则由大块状共晶组织逐渐破碎、溶解为小颗粒状组织,其面积分数随固溶处理时间的延长逐渐减少。固溶处理后接头发生了"软化"现象,焊核区的显微硬度下降明显,最大下降幅度超过20%。接头的抗拉强度随固溶时间的延长呈现先升高后降低的趋势,而伸长率则逐渐提高。当固溶时间为2 h时,接头抗拉强度达到最高,较原接头提高32.5%,约为母材的85.5%。
The solution treatment tests were carried out on Mg-6Zn-1Gd alloy friction stir welded joints. Effects of solution treatment processes on microstructure and mechanical properties of the friction stir welded joints were investigated by means of OM, SEM, EDS analysis methods, micro-hardness test and room temperature tensile test. The results show that the average grain size of the weld nugget increases with prolonging solution time, and the growth speed increases significantly when the solution time exceeds 2 h. The average grain size reaches 46 I.Lm when solution-treated for 4 h,which about 3.5 times than that of the untreated one. However,the large bulk eutectics are gradually broken and dissolve to small particulate eutectic, and the area fraction of eutectics decreases gradually with prolonging solution time. A softened phenomenon occurs in the weld nugget after solution treatment. The micro-hardness of the weld nugget decreases gradually with prolonging solution, and the maximum decreasing range exceeds 20%. Whatever, the tensile strength exhibits increasing firstly and then decreasing with the extension of time, while the elongation increases all the time. The highest tensile strength of the joint is obtained when solution-treated for 2 h, which improves by 32.5% compared with the original joint, and reaches 85.5% of the base material.
出处
《金属热处理》
CAS
CSCD
北大核心
2017年第5期127-133,共7页
Heat Treatment of Metals
基金
广东省科技厅科技计划项目(2014B030301012
2014B090907008
2013B091602002)
广州市科技计划项目(201509010003
201604010104)
关键词
镁合金
搅拌摩擦焊
固溶处理
magnesium alloy
friction stir welding
solution treatment
