Abstract
The transformation of rapidly solidified structures during preheating and extrusion has been investigated by using X-ray techniques and transmission electron microscopy. It was found that the rapidly solidified phases are generally unstable at processing temperatures and transform to equilibrium phases upon exposure to temperatures greater than 400°C. Transformation is an order of magnitude faster under the influence of stress during an extrusion cycle. The effect of increasing compact preheat time leads to substantial coarsening of the microstructure, which has an adverse effect on the mechanical properties. The effect of preheat time–temperature cycles has been investigated by comparing the microstructure and mechanical properties of extrudates produced from induction heated compacts (preheat time 4–5 min) and air heated compacts (preheat time 75 min).Significant property improvements are obtained in extrudates produced from rapidly heated compacts. The results indicate that the properties vary significantly if the preheat time–temperature cycles are varied.
MST/196
Get full access to this article
View all access options for this article.