The SEED Technology for Semi-Solid Processing of Aluminum Alloys: A Metallurgical and Process Overview

Abstract

As part of the foundry technology program, Alcan is developing a liquid-based slurrymaking process known as the SEED technology for semi-solid forming. The technology is presently entering the industrial and commercial stages, and will be used by the first customers in late 2006. The semi-solid process offers many advantages to economically fabricate near-net-shape parts having superior quality. The SEED process helps to overcome problems experienced with thixocasting and especially the high cost of feedstock. The SEED process involves two main steps: 1) heat extraction to achieve a desired liquid/solid mixture, and 2) drainage of an excess liquid to produce a self-supporting semi-solid slug that is formed under pressure. An overview of the industrial SEED technology advantages such as the alloy processing flexibility (A356, AA6061) and large slug dimensions and weights, is presented. The influence of the SEED processing parameters (slurry preparation) on the final mechanical properties and the microstructure evolution is also reported.