Effets des échanges thermiques sur l'écoulement de l'alliage semi-solide mis en forme par thixoextrusion

Abstract

Le comportement d’un alliage mis en forme à l’état semi-solide n’est toujours pas bien compris. Afin d’établir l'influence de différents paramètres sur l'écoulement de la matière, un processus de thixoextrusion expérimental a été réalisé sur un acier. Les effets de la température initiale du lopin et de l’outillage, de la vitesse de mise en forme et de la présence d'une couche de Ceraspray® à l'interface de l'outil et du lopin ont été étudiés par des expériences et confrontés à la simulation.

Semi-solid processing is an innovative technology for near net-shape production of components, where the metallic alloys are processed in the semi-solid state. Taking advantage of the thixotropic behavior of alloys in the semi-solid state, significant progress has been made in semi-solid processing. However, the consequences of such behavior on the flow during thixoforming are still not completely understood. To explore and better understand the influence of the different parameters on material flow during thixoextrusion process, thixoextrusion experiments were performed using the low carbon steel C38. The billet was partially melted at high solid fraction. Effects of various process parameters including the initial billet temperature, the temperature of die, the punch speed during process and the presence of a Ceraspray layer at the interface of tool and billet were investigated through experiments and simulation. After analyzing the results thus obtained, it was identified that the aforementioned parameters mainly affect thermal exchanges between die and part. Furthermore, the thermal effects can affect the material flow which is composed of various distinct zones.