Influence of Microstructure on the Mechanical Properties of Laser-Welded Joints between Different Classes of Automotive Steels

The need to reduce vehicle weight without compromising safety drives the use of advanced high-strength steels (AHSS) in the automotive industry. Laser welding is a widely employed technique for joining dissimilar materials due to its high precision and small heat-affected zone (HAZ). However, differences in the chemical composition and thermomechanical properties of the materials can create heterogeneous microstructures in the fusion zone (FZ) and HAZ, directly impacting the mechanical properties of the welded joint. This study aims to evaluate the relationship between microstructure and mechanical properties in laser-welded joints of dissimilar automotive steels. The objective is to understand how microstructural transformations affect weld strength, ductility, and toughness, contributing to process parameter optimization and improved structural performance. Microstructural analysis will be performed using optical microscopy, and mechanical tests, such as tensile testing and microhardness, will be conducted to correlate microstructural changes with the mechanical properties of the welded joint. It is expected that laser welding will result in a hardened HAZ due to the high cooling rate, which may reduce ductility and increase hardness in the welded region. Differences in the chemical composition of the base materials may lead to the formation of brittle phases in the FZ, affecting the joint's strength and toughness. The findings of this study will provide essential insights for improving the welding process and ensuring greater structural reliability in automotive applications.