OBTAINING SUB-MICRON GRAIN SIZE IN AM60 MAGNESIUM ALLOY USING FRICTION STIR PROCESSING

Friction stir processing (FSP) has gained important relevance in recent years as a very useful tool to produce ultra fine grain (UFG) microstructures (less than 500 nm) in cast and wrought magnesium and aluminum alloys, achieving superplastic behavior. In this work, the influence of initial material condition and cooling rate on microstructure (in particular in the final grain size) and hardness of an AM60-6 mm thick magnesium alloy was analyzed. A MP159 fix pin tool for 3 mm butt joints was used. FSP tests were conducted on as-cast and solubilized plates. Particular attention was paid to the level of grain refinement when a cooper backing plate and a cooling agent are used. A sub-micron grain size was obtained when these vigorous cooling systems were employed.