A Heat-treatable (AA 6082) and a non-heat treatable (AA 5083) aluminium alloys were friction stir lap welded to copper using the same welding parameters. Macro and microscopic analysis of the welds enabled to detect important differences in welding results, according to the aluminium alloy type. Whereas important internal defects, resulting from ineffective materials mixing, were detected for the AA 5083/copper welds, a relatively uniform material mixing was detected in the AA 6082/copper welds. Micro-hardness testing and XRD analysis also showed important differences in microstructural evolution for both types of welds. TEM and EBSD-based study of the AA 5083/copper welds revealed the formation of submicron-sized microstructures in the stirred aluminium region, for which untypically high hardness values were registered.

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Friction stir processing (FSP) is a promising technique for improving plasticity of magnesium alloys through the homogenization and grain refinement of their structure. In this study, a magnesium alloy AZ31 has been processed by FSP to achieve an ultrafine grain size structure (700 nm), and the oxide films formed spontaneously on the surface of the FSP zone are compared with those on the unprocessed material. Chemical composition of the oxide films are analyzed by XPS.The natural oxide films, close to 36 nm, can be described as a structure of (MgO)/Mg(OH) 2 with the outermost surface mainly formed by Mg(OH) 2 /MgCO 3 . About 5-7 at.% of Al 3+ is distributed through the oxide layer. Segregated zinc enrichment (Zn 2p 3/2 at 1021.4 eV) at the interface oxide/metal is found. The FSP samples show higher carbonatation degree at the surface and a lower segregated zinc percentage at the interface oxide/metal.

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