Enhanced formability of superplastic AlMgZr alloys made by particulate routes

The technique of centrifugal atomisation has been used to produce a number of AlMgZr alloy particulates with Zr contents up to 1%. These have been converted into sheet by extrusion, rolling and heat treatment and their superplastic properties determined. It has been found that control of the solidification conditions during atomisation is crucial in order to maximise Zr solid solubility and achieve a fine dispersion of Al3Zr precipitates. Superplastic behaviour is enhanced at higher Zr contents, and by thermo-mechanical processing to achieve ductilities in excess of 600% at strain rates of 0.01 s-1. Alloy conditioning was found to have a significant effect on the Al3Zr precipitate size, with coarser precipitates relating to premature failure during testing. This paper describes the atomisation process and identifies the key parameters that must be controlled for its successful operation. A summary of the superplastic performance of the product will be included.