ECAE as a thixoforming raw material process

Abstract

There are few commercial alloys available for processing in the semi-solid state, notably the A356 and A357 alloys, both based on Aluminium-Magnesium-Silicon system. In recent projects, it was developed new alloys in the aluminum-silicon-copper system which generated seven patents (four international: BR200805448-A2, BR200805449-A2, A2-BR200805450, BR200805451-A2). The Foundry Laboratory of the Faculty of Mechanical Engineering Unicamp has a system of continuous casting by electromagnetic stirring that produces these same alloys, but with generating average particles sizes of up to 150¼m, even with the use of grain refiners. The proper control of the grain size is essential to this technology, since the smaller the grain better viscous behavior during thixoforming. This project aims to present a new approach for the production of these alloys, specially designed for thixoforming operations, starting with the traditional A356 (Al-6,5wt%Si-0,5wt% Mg), via Direct casting followed by ECAE (Equal Channel Angular Extrusion), that, as will be shown, will result in a microstructure with fine-grained, up to 50¼m, without the use of grain refiners. The goal is to develop and test a simple and inexpensive way to prepare these materials. Thus the scientific initiation was designed to search further development of the technology for production and characterization of new alloys for applications in semi-solid state in a pilot scale. It is important to notice that, the student will start its work with the preparation and its initial characterization of the raw material and will continue to work on his master science, with the study of the morphology evolution of this raw material to the during semi-solid stage, and will make the corresponding evaluation of the Rheological behavior. (AU)