Heat treatment of 319.2 aluminium automotive alloy Part 1, Solution heat treatment

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Abstract
Heat treatment is one of the important controlling factors used to enhance the mechanical properties of an alloy casting. This involves optimizing both the solution heat treatment and the ageing treatment given to the alloy. This paper on 319.2 alloy (an important aluminium alloy for automotive applications) constitutes the first part of a study of the heat treatment of this alloy, and covers a detailed investigation of the factors controlling the choice of solution heat temperature and time and their impact on the mechanical properties. The results indicate that, for the range of solution temperatures and times studied, the optimum treatment is 8 h at 515 °C. Higher temperatures accelerated the partial melting of the Al2Cu phase (present in the as-cast structure), resulting in a structureless phase and associated shrinkage porosity, both of which degrade the mechanical properties. An alternative two-step solution treatment process that gives better ductility as well as high strength levels has been proposed. The quality index (Q) shows a relationship similar to that observed in aged A356 alloy.