Recovery or Non-Recovery in Al-0.1% Mg and Al-1% Mg Alloy during High-Pressure Torsion Processing

Abstract

The Al-1% Mg and Al-0.1% Mg alloys were both processed by high-pressure torsion (HPT) at room temperature. In the Al-1% Mg alloy, the hardness values in the disc centre area are lower than in the disc edge area after 1/2 and 1 turn, and the area of lower hardness values in the disc centre decreases as the number of turns increases from 1/2 to 1 turn. Finally, the hardness values are reasonably homogenous along the disc diameter as the number of turns increases to 5 and 10 turns. The Al-0.1% Mg alloy displays a different hardness evolution behavior: the hardness values in the disc centre are higher than at the disc edge 1/2 and 1 turn, and the area of higher hardness values decreases as the numbers of turn increases from 1/2 to 1 turn. The hardness values evolve towards homogeneity along the disc diameter after 5 and 10 turns. EBSD microstructure investigations in the Al-0.1% Mg alloy reveal that a few low-angle boundaries exist at the disc edge after 1/2 turn. It is suggested that the higher hardness values in the disc centre in the Al-0.1% Mg alloy are related to rapid recovery at the disc edge where the material is subjected to heavy straining.