Superplastic behaviour of friction stir processed AZ91 magnesium alloy produced by high pressure die cast

The room temperature and hot tensile properties of AZ91 magnesium alloy produced by high pressure die cast after friction stir processing (FSP) were studied in the present paper. Such process is a modification of classical friction stir welding one in which the sheets are not joined but the stirring action of the tool, on the bulk material, is used to refine the microstructure in order to increase the mechanical properties of the metal such as yield strength, fatigue life and possible superplastic properties at relative low temperature and high strain rates [R.S. Mishra, Z.Y. Ma, Mater. Sci. Eng. R 50 (2005) 1–78]. The material was FSP after solution treatment and the superplastic behaviour was analysed by means of hot tensile tests, in longitudinal direction, in the temperature and strain rate ranges of 225–300 °C and 10−2 to 10−4 s−1, respectively.