Solidification and Heat-treatment Conditions Affecting the Tensile Properties and Fracture Feature of an Automotive AlSiMg Alloy

Abstract

In this work, a study on the interrelationship between the solidi cation and heat-treatment processes parameters with tensile properties and fracture feature was performed with an automotive AlSiMg alloy. For that, samples of the horizontally solidi ed Al7Si0.3Mg (wt.%) alloy were subjected to the T6-heat treatment as well as tensile tests were performed on both investigated samples, under conditions established from the literature. The solidi cation conditions such as growth and cooling rates and the secondary dendritic spacing (V L and T R and λ 2 , respectively) and their effects on the ultimate tensile strength (σ UTS ) and elongation (E%) were evaluated. It was observed higher σ UTS values in the heat-treated samples and ner microstructures have inherited a better E% performance. Analysis by SEM/EDS fractography on both samples showed a mix between brittle and ductile fractures, constituted by cleavage facets, secondary cracks, facets covered with micro-voids, tear ridges and dimples. It has allowed deducing on the occurrence of a transition from ductile to brittle fracture along the solidi ed ingot as well as the predominance of brittle fracture in the heat-treated samples.