The Influence of Strontium on Microstructural and Rheological Behavior of the Semi-solid A380 Aluminum Alloy

Abstract

This article aims to correct the lack of information regarding the combined effect of grain refinement and strontium modification on the microstructure and rheological behavior of semi-solid slurries. The A380 aluminum alloy was studied in the semi-solid state in three different conditions: as received, grain refined and grain refined/modified with Sr. To determine the semi-solid temperature, a DSC analysis and Thermo-calcÒ simulations were used. SEM, optical and polarized light microscopy analyses were performed to analyze the microstructural changes caused by the refiner and modifier agents as well as to evaluate the morphological evolution of the alloys in the semi-solid state. The rheological behavior was studied with a hot compression test between parallel plates. The main results show that the addition of Sr, besides its influence on the Si and Fe-b particles, also leads to a better globularization of a-Al phase particles in the semi-solid state. Furthermore, the rheological analysis of stress vs strain and apparent viscosity vs average shear rate also point to a better behavior of the alloy in the semi-solid state after Sr modification, thus indicating that Sr addition could improve the performance of the A380 alloy as a semi-solid feedstock.