搅拌摩擦焊接Al-Mg-(Zn) 合金的腐蚀行为

Corrosion Behavior of Friction Stir Welded Al-Mg-(Zn) Alloys

摘要:

本文研究了搅拌摩擦焊接含Zn Al-Mg合金的腐蚀行为及焊后热处理对搅拌摩擦焊接合金腐蚀行为的影响。结果表明,经焊后热处理后不同焊接区的最大腐蚀深度和主导腐蚀模式随Zn含量增加而发生明显变化。Zn的加入使主导腐蚀模式由晶间腐蚀变为点蚀。与加工硬化态合金相比,时效硬化态合金具有严重的电偶腐蚀倾向。对于析出强化Al-Mg-Zn合金而言,这在很大程度上与不连续分布的晶界析出相及丰富的晶内析出相的形成密切相关,而对无Zn的Al-Mg合金,其则与连续分布的晶界β-AlMg相相关。

Abstract:

The corrosion behavior of friction stir welded Zn-modified Al-Mg alloys are systematically investigated as well as the effects of pre-weld temper conditions on the corrosion behavior of the friction stir welded alloys. Both maximum corrosion depth and dominating corrosion mode in different weld regions after post welding heat treatment show obvious variations with an increase in the Zn content. With Zn additions the dominating corrosion mode changes from intergranular corrosion to pitting corrosion, and the severe galvanic corrosion tendency obviously occurs in the precipitation hardened alloys compared to that of the strain hardened alloy. This would be greatly related with the formation of discontinuously distributed grain boundary precipitates as well as abundant intragranular precipitates (mainly T-AlZnMgCu phase) in the precipitation hardened Al-Mg-Zn alloys while it is in line with the continuously distributed β-AlMg phase along grain boundary in the Zn-free Al-Mg alloys.