Underwater friction stir welding of ultrafine grained 2017 aluminum alloy

Abstract

2017 aluminum alloy plates with an ultrafine grained (UFG) structure were produced by equal channel angular processing (ECAP) and then were joined by underwater friction stir welding (underwater FSW). X-ray diffractometer (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) and microhardness tester were adopted to investigate the microstructural and mechanical characteristics of the FSW joint. The results indicate that an ultrafine grained microstructure with the mean grain size of ∼0.7 μm is obtained in the weld nugget by using water cooling. However, The FSW joint exhibits softening compared with the ultrafine grained based material and the heat affected zone (HAZ) has the lowest hardness owing to the coarsening of the strengthening precipitates.

Keywords

ultrafine grained structure / equal channel angular processing / aluminum alloy / underwater friction stir welding

References

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