Effect of solute elements on grain refinement during friction stir processing in high-purity aluminum

摘要

Friction stir processing (FSP) is one of the severe plastic deformation (SPD) processes. It has been reported that SPD-processed Al with various purities attained a minimum grain size when Zener-Hollomon parameter is larger than 10~(16) s~(-1). The minimum grain size is different by purity level and alloying elements. We investigated the influence of Fe solute atoms on grain refinement of high-purity Al on the condition that Zener-Hollomon parameter was larger than 10~(16) s~(-1). FSP was conducted on Al-0.01%Fe, which was fabricated by using 5N Al (99.999% purity). After FSP, Al-0.01%Fe exhibits the minimum grain size of 1.4 μm, although high-purity aluminums with more than 99.998% exhibits much larger minimum grain sizes of 30-40 μm. Only 101 at.ppm Fe played a critical role in the grain refinement of pure aluminums.