Analysis on microstructure and mechanism of high temperature oscillation heat treatment after friction stir welding

DONG Fengbo; FENG Xiaosong; LUO Chuanhong; HUANG Chuanzhen; LIU Dashuang

doi:10.7512/j.issn.1001-2303.2020.06.04

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Analysis on microstructure and mechanism of high temperature oscillation heat treatment after friction stir welding
Vol. 50, Issue 6, Pages: 26-29(2020)
DOI： 10.7512/j.issn.1001-2303.2020.06.04

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DONG Fengbo, FENG Xiaosong, LUO Chuanhong, et al. Analysis on microstructure and mechanism of high temperature oscillation heat treatment after friction stir welding. [J]. 50(6):26-29(2020)
DOI：

DONG Fengbo, FENG Xiaosong, LUO Chuanhong, et al. Analysis on microstructure and mechanism of high temperature oscillation heat treatment after friction stir welding. [J]. 50(6):26-29(2020) DOI： 10.7512/j.issn.1001-2303.2020.06.04.

摘要

针对2219-O铝合金搅拌摩擦焊接头焊点热处理过程中易出现异常晶粒(AGG)长大现象的问题,对焊接接头进行高温振荡固溶热处理,并对热处理前后的接头微观组织进行了分析。结果表明,搅拌摩擦焊形成的焊缝热稳定性较差,晶粒较容易再热长大,常规热处理晶粒尺寸达毫米级;围绕固溶温度下限作高温振荡固溶热处理能够有效地抑制粗大晶粒的产生,当温度振荡幅度大于90℃,焊核晶粒为直径约20μm的细晶。

Abstract

Friction stir welding（FSW） was used to weld 2219-O aluminium alloy. The welded joints were treated by high temperature oscillating solid solution heat treatment. The mechanism of abnormal grain growth of FSW joints was studied by analyzing the microstructures before and after heat trea-tment,and the corresponding restraining measures were put forward. The results show that the thermal stability of the weld formed by FSW is poor,the grain is easy to reheat and grow,and the grain size after conventional heat treatment reaches millimeter level. High temperature oscillating solid solution heat treatment around the lower limit of solution temperature can effectively restrain the formation of coarse grains. When the temperature oscillation amplitude is greater than 90 ℃,the grain size of the nugget is about 20 μm in diameter.