Examining the microhardness evolution and thermal stability of an Al-Mg-Sc alloy processed by high-pressure torsion at a high temperature

An Al-3% Mg-0.2% Sc alloy was solution treated and processed through 10 turns of high-pressure torsion (HPT) at 450 K. Afterwards, the HPT-processed alloy was annealed for 1 h at temperatures ranging from 423 to 773 K and its mechanical properties and microstructural evolution were examined using microhardness measurements and electron backscattered diffraction (EBSD) analysis. The results demonstrate that HPT processing at an elevated temperature leads to a more uniform microhardness distribution and to an early saturation in the hardness values in the Al alloy compared with high-pressure torsion at room temperature. In addition, detailed EBSD analysis conducted on the HPT-processed samples immediately after annealing revealed that the Al-Mg-Sc alloy subjected to HPT processing at 450 K exhibits superior thermal stability by comparison with the same material subjected to HPT at 300 K.