Characterization and Analysis of Brazed Aluminum-Zinc Coated Steel Joints

The automotive industry constitutes an important pillar in the world economy and has drastically changed how people live and work in a way that was unimaginable in the past. Automotive industry in Italy as well plays a key role in its economic development given the jobs it provides in entire value chain from design of components to the manufacturing of finished products. Although critical and essential in today’s world, industry is under tremendous pressure to optimize its performance and efficiency to keep up with high standards in terms of the environment and achieve fuel efficiency. One of the key factors affecting these indicators is the weight of a vehicle which consequently requires more fuel consumption and hence more harmful gases. The motivation to replace high strength heavy material with combination of lightweight aluminum with steel while keeping the strength and integrity of the components greatly solves these challenges. Additionally, this technique equally benefits the EV sector which would result in more efficient battery consumption. However, the challenge lies in optimal joining of lightweight aluminum to more heavy high strength steel without any compromises. This thesis is an effort in the same sense to test joining zinc coated steel with aluminum alloys using brazing technique under different conditions of brazing. The experimental activity investigated the possibility of joining AL-6016 alloy with zinc coated steel and pure zinc as a brazing alloy with and without the application of aluminum flux. The Joining area and reaction side is investigated with optical microscope, SEM, EDS, and micro hardness test. XRD technique has also been exploited to find residual stresses in the materials and find phase constituents on the reaction side of samples. Joining was achieved in both cases, however discontinuities were observed which were different in each case. Better joining between aluminum side and brazing alloy was observed in case of flux while joining was more continuous towards zinc coated steel with brazing alloy when flux was not used.