Structure and mechanical properties of Al–Ca alloys processed by severe plastic deformation

Abstract

The study investigated the effect of deformation by high-pressure torsion (HPT) on the hardening, structure transformations, and thermal stability of two eutectic alloys: binary – Al-8.0% Ca and complex-alloyed – Al-3.5% Ca-0.9% Mn-0.5% Fe-0.1% Zr-0.1% Sc. The HPT-deformation of the alloys (5 revolutions) led to the formation of a nanocrystalline structure with a high density of crystal defects. A predominant grain size was 20–40 nm in the binary alloy and 11–34 nm in the complex alloy. HPT resulted in the refinement of the Al4Ca particles for the binary alloy and the transformation of the Al4Ca particles into nanoclusters and segregation for the complex alloy. HPT increased the microhardness of the binary alloy to 1.80–2.05 GPa (~2 times), and of the complex-alloyed alloy to 2.40–2.70 GPa (4.1–4.6 times). The hardening of the complex alloy is retained to higher heating temperatures compared to the binary alloy.