Friction stir processing of AM60B magnesium alloy sheets

The mechanical and microstructural properties of AM60B magnesium alloy resulting from the friction stir processing (FSP) were analysed in the present study. The sheets were produced by high-pressure die casting (HPDC) into the form of trial sheets 2.5 mm thickness and then friction-stir processed. The tensile mechanical properties were evaluated at room temperature in the longitudinal direction respect to the processing one. Tensile tests were also performed at higher temperatures and different strain rates in the nugget zone parallel to the processing direction, in order to analyse the superplastic properties of the recrystallized material and to observe the differences with the parent material as a function of the strong grain refinement due to the friction stir process. The dynamic recrystallized structure of the material was observed by employing optical and electron microscopy. The high temperature behaviour of the material was studied in the parallel direction, by means of tensile tests in the temperature and strain rate ranges of 150–300 °C and 10−2 to 10−4 s−1, respectively. The deformation behaviour in the high temperature regime (275–300 °C) is related to the grain boundary sliding (GBS) acting in the material parallel to the tensile direction, differing strongly from the lower temperature one in which the deformation is strongly linked to grain triple junctions fracture.