Optimization of casting parameters on an improved AA6061 aluminum alloy for semi-solid die casting

摘要

A study was conducted to assess the performance and castability of a new AA6061 aluminum alloy variant specially designed for semi-solid pressure die casting. The AA6061 alloy has very desirable mechanical properties for the fabrication of automotive parts. However, it has limited castability due to its low silicon content. It is not well suited for shape casting processes which are, for their part, very interesting in terms of production costs for complex-shaped automotive components. In an effort to meet automotive industry requirements, new AA6061 alloy variants have been developed by Rio Tinto Alcan researchers over the past years, aiming to improve the castability of the alloy while maintaining its desirable mechanical properties, by increasing its die-filling capacity, decreasing its hot tearing tendency. The study described herein is an example of how the performance of a single variant was assessed in terms of castability. The full study was conducted on six separate variants. A part simulating a car suspension arm was die-cast for this study. Tests were carried out by varying the casting parameters of the die-casting press and by optimizing parameters of the semi-solid slurry production. In all, nine parameters were involved in the study. The study was based on a new design of experiment method that builds on past experience: E.M. Method*. Work performed in this study allowed unbiased comparisons of the filling capacity and hot-tearing tendency of several AA6061 alloy variants. The optimum operational parameters for a variant of alloy AA6061 were defined after a relatively low number of tests, a cost- and time-saving approach since the study had to be repeated six times.