Abstract
Joining of steel- aluminum thin sheets (0.8 to 2 mm) has been extensively studied in the beginning of 2000 years for automotive applications, in a regard to reduce vehicle weight (European Project Super Light Car). In this context, this work is carried out to study the possibilities of dissimilar steel-aluminum assembly by the new variant of the MIG welding process known as CMT (Cold Metal Transfer). The first part of the study is devoted to understand the operating principle of this process, using a platform equipped with a data acquisition system for synchronized measurements of voltage, current, speed wire feed and video images taken by a speed camera. In a second part, we present the metallurgical properties of steel-aluminum joints made in lap configuration with parameter sets covering the entire range studied in the previous section. We are especially interested in the area creating the connection between steel and aluminum. In the third part, the mechanical proprieties of connections are evaluated by quasi-static transverse tensile tests and under cyclic loading. The breaking strength of the reaction layer is also evaluated by an original technique, usually dedicated to the evaluation of the adhesion of coatings by laser shock. Finally, we propose a new method to estimate the efficiency of the CMT process based on the finite element numerical simulation of the evolution of temperature fields during the deposition of an aluminum weld on a galvanized steel substrate, coupled with modeling of the growth of the reaction layer formed along the steel / aluminum interface.