中國(guó)有色金屬學(xué)報(bào)(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 20 No. 9 September 2010 |
high solid fraction hot-crack-sensitive aluminium alloys
（1. Thixo Unit, B56, University of Liège, 4 Boulevard de Colonster, Sart Tilman, 4000 Liège, Belgium;
2. Special Metallic Materials, B52, University of Liège, 1 Chemin des Chevreuils, Sart Tilman, 4000 Liège, Belgium）
Abstract:Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<φs<1), which involves the processing of alloys in the semi-solid state. Tooling has to be adapted to this particular process to benefit shear thinning and thixotropic behaviour of such semi-solid material. Tooling parameters, such as the forming speed and tool temperature, have to be accurately controlled because of their influence on thermal exchanges between material flow and tool. These thermal exchanges influence the high-cracking tendency and the rheology of the semi-solid material during forming, which affects parts properties and therefore their quality. Extrusion tests show how thermal exchanges influence quality of thixoforged parts made of 7075 aluminium alloys at high solid fraction by modifying process parameters like forming speed, tool temperature and tool thermal protector. Thus an optimum in terms of thermal exchanges has to be found between surface quality and mechanical properties of the part. A direct application is the evaluation of surface quality of thixoforged thin wall parts made of 7075 aluminium alloy.
Key words: thixoforging; solid fraction; near-net-shaping; tooling; 7075 aluminium alloys
