Achieving Nanograin size In AZ31 Mg Alloy by Submerge Friction Stir Processing

Friction stir processing (FSP) has been established as significant grain refinement technique [1]. Also FSP has been demonstrated to be an effective means of refining grain size of cast or wrought aluminum based via dynamically recrystallization. . Success FSP of Mg –based alloys refining the microstructure of the alloys down to 1-5 μm have been widely reported recently [2-4]. For Mg or solute solution hardened Mg alloys with a low content of alloying element , it is difficult to achieve a UFG microstructure due to grain growth of the single – phase grains [5]. In this study submerge FSP is used to prepare nano grain AZ31 Mg alloys. With just single pass under effective cooling and suitable parameters process, the mean grain size of the obtained specimen can be refined to an nano grain (200-500) which is much finer than previous SPD result[6]. The working temperature and strain rate, combined and expressed by Zener-Holloman parameter