7N01S-T5铝合金厚板搅拌摩擦焊接头的晶间腐蚀行为
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摘要
本研究对14 mm厚的7N01s-T5铝合金搅拌摩擦焊(FSW)试样沿板厚方向进行分层切片,采用OM和TEM等微观组织表征方法及晶间腐蚀性能测试手段,研究了接头各区的晶间腐蚀行为。实验发现,焊接接头各区域的腐蚀形貌存在明显的不同。接头的热影响区腐蚀程度最严重,其中热影响区上、下表层较中心层的腐蚀更严重,这主要归因于晶界处连续分布的析出相粒子和晶粒尺寸存在差异。热机影响区位于热影响区和搅拌区的过渡位置,晶粒扭曲变形,由于受到焊接的热循环作用,晶界析出相发生了部分溶解,腐蚀倾向性相对较低。搅拌区在FSW过程中经历了剧烈的塑性变形和温升,形成细小的等轴晶,析出强化相粒子发生了完全溶解,其晶间腐蚀倾向性最低。
In this work,the intergranular corrosion tests were conducted for the vertically-sliced samples of a friction-stir-welded( FSW),14 mm-thick7 N01 s-T5 aluminum alloy plate,and OM,TEM were employed to determine the intergranular corrosion behavior of different areas of the joint.The results showed that the different locations in welded joint have various corrosion morphology after intergranular corrosion test. The heat-affected zone( HAZ) of the weld exhibits the highest susceptibility to intergranular corrosion,in which the top and the bottom surface layers suffer more serious corrosion than the central layer. This can be ascribed to the continuously dispersed precipitates on grain boundary and the grain size. The thermo-mechanically affected zone( TMAZ) is a transition zone locating between the heat-affected zone and the stir zone,and characterized by a highly deformed structure. However,TMAZ is relatively less susceptible to intergranular corrosion,owing to the thermal cycle it experienced and the partial re-dissolving of the precipitates on the grain boundary. The stir zone( SZ) experiences severe plastic deformation and temperature cycling during FSW process,which results in a fine grain equiaxed structure,and in consequence,complete re-dissolving of the precipitates.Hence SZ can be considered most insensitive to intergranular corrosion.
In this work,the intergranular corrosion tests were conducted for the vertically-sliced samples of a friction-stir-welded( FSW),14 mm-thick7 N01 s-T5 aluminum alloy plate,and OM,TEM were employed to determine the intergranular corrosion behavior of different areas of the joint.The results showed that the different locations in welded joint have various corrosion morphology after intergranular corrosion test. The heat-affected zone( HAZ) of the weld exhibits the highest susceptibility to intergranular corrosion,in which the top and the bottom surface layers suffer more serious corrosion than the central layer. This can be ascribed to the continuously dispersed precipitates on grain boundary and the grain size. The thermo-mechanically affected zone( TMAZ) is a transition zone locating between the heat-affected zone and the stir zone,and characterized by a highly deformed structure. However,TMAZ is relatively less susceptible to intergranular corrosion,owing to the thermal cycle it experienced and the partial re-dissolving of the precipitates on the grain boundary. The stir zone( SZ) experiences severe plastic deformation and temperature cycling during FSW process,which results in a fine grain equiaxed structure,and in consequence,complete re-dissolving of the precipitates.Hence SZ can be considered most insensitive to intergranular corrosion.
引文
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3 Thomas W M,Nicholas E D,Needham J C,et al. Great Britain patent applioation,No. 9125978. 8,1991.
4 Joel D. Welding Journal,2001,80(5),30.
5 Mishra R S,Ma Z Y. Materials Science and Engineering R Reports,2005,50(1),1.
6 Marlaud T,Malki B,Henon C,et al. Corrosion Science,2011,53(10),3139.
7 Song R G,Dietzel W,Zhang B J,et al. Acta Materialia,2004,52(16),4727.
8 Liu D Q,Ke L M,Xu W P,et al. Journal of the Chinese Society of Corrosion&Protection,2017,37(3),293(in Chinese).刘德强,柯黎明,徐卫平,等.中国腐蚀与防护学报,2017,37(3),293.
9 Wadeson D A,Zhou X,Thompson G E,et al. Corrosion Science,2006,48(4),887.
10 Rao T S,Reddy G M,Rao G S,et al. International Journal of Materials Research,2014,105(4),375.
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