热处理对磁场作用下AZ91镁合金焊接接头组织和性能的影响

Effects of post weld heat treatments on microstructure and mechanical properties of AZ91 magnesium alloy joints welded by TIG method with adding magnetic field

对5 mm厚的AZ91镁板进行钨极氩弧焊的过程中,外加纵向交流磁场,并在焊后进行固溶、固溶时效和时效处理.通过对接头显微组织和力学性能分析,研究磁场参数对热处理后AZ91焊接接头组织和性能的影响规律.结果表明,磁场作用下的AZ91镁合金焊接接头比未施加磁场的焊接接头经固溶处理后晶粒更加细小;经固溶时效处理后更多细小弥散的β-Mg17Al12相大量在α-Mg上析出;经时效处理后析出的β-Mg17Al12相更加细小、断续、分散,且施加磁场的焊接接头比未加磁场的焊接接头热处理后硬度、强度和塑性都得到提高.

AC magnetic field was employed in welding of5 mm thick AZ91 magnesium alloy plate by TIG method. The effects of post weld heat treatment on properties and microstructure of welded joints were studied through the analysis of the microstructure,mechanical properties and corrosion resistance. The results showed that the grain size was refined for AZ91 magnesium alloy joint with solution treatment; and more dispersed β-Mg17Al12 phase precipitates in α-Mg were found for the joint with solution and aging treatment; intermittent and dispersal precipitations of β-Mg17Al12 phase was smaller for joint with aging treatment. Meanwhile,the hardness,strength and plasticity of the weld joints were improved after heat treatment.