Investigation of superplasticity and dynamic grain growth in ultrafine-grained Al-0.5%Mg-Sc alloys

摘要

The effect of Sc on plasticity at elevated temperatures(from 300 to 500 degrees C) and strain rates(from 10(-3) to 10(-1) s(-1))of ultrafine-grained (UFG) Al-0.5%Mg-Sc alloyswas investigated. In the UFG alloys with 0.4% and 0.5%Sc at 500 degrees C and strain rate 1.10(-1) s(-1), high elongation to failure (similar to 1060%) was achieved. The fractographic analysis of the fracturesin the Al-0.5%Mg alloy demonstrated the crack growth zone to occupy almost whole fracture area.The self-destruction in the crack growth zone has a viscous character.In the UFG alloys with Sc, numerous pits formed as a result of micropore junction were observed. Dependencies of dynamic grain growth (DGG) rate on the temperature and strain rate were determined. The DGG in the Al-0.5%Mg-Sc alloys was found. The kinetics of the DGG in the Al-0.5%Mg-0.2%Sc alloy was shown to be limited by mobility of junction disclinations. In the Al-0.5%Mg-0.5%Sc alloy, it is limited by mobility of oriented misfit dislocations. Al3Sc particles were shown to be possible origin of the micropore formation and of accelerated destruction of the Al-0.5%Mg-Sc alloys at high temperature deformation. (C) 2021 Elsevier B.V. All rights reserved.