Thixoforming Steel

Your mobile phone or laptop almost certainly has a casing made by thixoforming magnesium alloy. You may well drive a car with a thixoformed aluminium alloy fuel rail. However, as yet, steel is not commercially processed by any of the routes which involve forming in the semi-solid state with the microstructure consisting of spheroids of solid in a liquid matrix. The main reasons for this are high working temperature, oxidation and die degradation. Steel oxidizes as the material is reheated into the semisolid state for forming (and that oxide can then get incorporated into the component as the material flows into the die causing defects). Special precautions therefore have to be taken to minimise oxidation. Using conventional die materials, die degradation with semi-solid steel flow is severe. Overcoming this problem is a major challenge to those carrying out R&D in this area. However, if steel could be thixoformed there would be major advantages in terms of saving raw material and achieving near net shape for complex components in one shot.

A consortium of European universities, institutes and industrial companies came together in 2006 to develop the thixoforming of steels. The consortium is funded by the COST programme of the European Union and is called 'Thixosteel'. We have listed the partners at the end of this Foreword. Dr Ahmed Rassili of the Thixo Unit at the University of Liège in Belgium chairs the consortium and Professor Helen Atkinson of the University of Leicester in the UK is the Vice-Chair. The chapters presented in this book, which aims to summarise the state-of-the-art in thixoforming steel, have been written by members of the consortium. This book follows one published in 2008 by the consortium on 'Modelling of Semi-Solid Processing'.