DEVELOPMENT OF THIXO TRANSVERSE FORGING PROCESS FOR THE PRODUCTION OF STEEL-ALUMINUM HYBRID STRUCTURES

Abstract

Iron and aluminum alloys are among the most important materials in automotive industry because of their good properties. Combining both materials in a hybrid structure will implement the integrated load-supporting of steel with the advantages of aluminum in weight reduction. However, due to the highly differing physical and mechanical properties, metallurgical bonds between these materials are difficult to achieve with traditional welding methods. These differences in properties lead to the formation of hard and brittle intermetallic compounds (IMC) along the transition line which will significantly decrease the mechanical properties of the joining area. Production of hybrid components by thixoformig of aluminum on steel is a promising method to manufacture near net shape components with good mechanical properties in a single process step. This process allows to join dissimilar materials in semisolid state at lower temperatures than traditional welding methods, causing a decrease in thickness of the intermetallic layer. In this work, the mount of the front cradle of the car was manufactured in A356 aluminum alloy and joined to a S355JH2 quality steel tube in one step by thixo transverse forging method. In order to determine the quality of the component and the joint a complete mechanical and a qualitative metallographic analysis was carried out. The results revealed that quality hybrid components can be achieved regarding the intermetallic bond, although geometric redesign is necessary to reduce local stresses. Keywords: Aluminum-Steel hybrid structures, Semi-solid, joining, Intermetallic phase, Thixoforming, Lightweight.