Mechanical behavior of alloys with equiaxed microstructure in the semisolid state at high solid content

The mechanical response in compression of A2014 and Al-4 wt% Cu alloys with equiaxed microstructure in the semisolid state at high volume fraction of solid (>0.6) is studied. When the amount of liquid is low, deformation in compression is highly non-uniform due to strain localization. In the range of conditions examined no phase segregation was detected. The stress-strain curve exhibits a peak at low strain, around 5-10%, and then decreases to a plateau value. Secondary phase particles in A2014 that remain solid in the semisolid range of the alloy are responsible for the lower peak and higher plateau stress compared to Al-4 wt% Cu alloy. The effect of the grain size for the alloys tested was small. Strain rate jump experiments show that the instantaneous strain rate sensitivity in the semisolid state is similar to that of the solid phase. As the volume fraction of solid decreases, the plateau stress becomes rate insensitive to the strain rate jump. The results allow the relative importance to be assessed of various mechanisms responsible for resistance to flow of semisolid alloys with equiaxed microstructure in compression. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd All rights reserved.