Prediction of extruded microstructures using experimental and numerical modelling techniques

摘要

Aluminium is a valuable material with an ever-expanding amount of uses. However as the use of aluminium increases so do the demands on its properties - both mechanical and physical. After the casting of a specific alloy the only method of altering the microstructure and consequently the properties of that alloy is by thermomechanical processing. In some cases extruders require a particular final microstructure in order to attain specific mechanical properties for product safety reasons, for example in structural applications. In others the resulting, although undesired, microstructure is an almost accepted part of the process, for example peripheral coarse grain in the extrusion of hard alloys. In this study, the formation of the final extruded microstructure was investigated as a function of the strains, strain rates and temperatures produced in the aluminium extrusion process. The strains, strain rates and temperatures are themselves a function of a particular extrusion die design and process control. The investigations were carried out using a combination of industrially extruded metal, laboratory scale experimentation and Finite Element Modelling of the whole extrusion process. This paper will introduce the current findings on the development of fundamental techniques that can be used within industry to predict the microstructures of extruded products. The ultimate aim is that the same techniques can then be used to specify extrusion die design and process control parameters in order to accurately produce the required extruded microstructures.