超声冲击实现7A52铝合金焊接接头表面纳米化

Surface nanocrystallization of 7A52 aluminum alloy welded joint using ultrasonic impact treatment

针对7A52铝合金焊接接头表面纳米化研究尚不成熟的实际情况,利用超声冲击技术,在预设电流为2 A,超声冲击速度为1.25 min/cm2的条件下,对7A52铝合金双丝MIG焊焊接接头进行超声冲击处理,借助扫描电子显微镜及透射电子显微镜对超声冲击处理后的7A52铝合金双丝MIG焊焊接接头的表层组织进行观察、分析.发现焊接接头表层经超声冲击处理后形成塑性变形层,焊缝及热影响区的变形层厚度可达70μm左右,母材的变形层厚度可达50μm左右.同时,焊接接头表层晶粒被细化,焊缝表层的晶粒尺寸可达70~300 nm,母材的晶粒尺寸可达50~500 nm.

Aiming at making the study of surface nanocrystallization on 7A52 aluminum alloy welded joint comprehensive,the tandem welded joint of 7A52 aluminum alloy was subjected to an ultrasonic peening with 2A of current and 1. 25 min /cm2 of impact speed. The microstructure of the surface layer of the welded joint after ultrasonic peening was characterized and analyzed by scanning electron microscope( SEM),and transmission electron microscopy( TEM) observations. After ultrasonic peening,the thickness of deformed surface layer of the welded joint was about 70 μm at weld metal( WM) and heat affected zone( HAZ),about 50μm at base metal( BM). The grains of the welded surface were refined in which the grain size of WM surface reached 70-300 nm,and the grain size of BM surface reached 50-500 nm.