Dissimilar linear friction welding between a SiC particle reinforced aluminum composite and a monolithic aluminum alloy: Microstructural, tensile and fatigue properties

摘要

The present work is aimed at evaluating the feasibility of the linear friction welding process to produce dissimilar joints between a AA2124/25%vol SiC_p composite and a 2024 Al alloy, illustrating and correlating their microstructural and mechanical properties. Optical microscopy (OM) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) were used to characterize the effects of the welding process on the microstructure of the LFW joints. Tensile tests were carried out on joints welded at three different welding parameters. Axial fatigue tests were carried out under stress control and the corresponding S-N probability curves were computed. The mechanisms of failure were investigated by SEM analyses of the fracture surfaces. In the LFW joints almost no blending between the MMC and the base Al alloy was detected, while good particle distribution and no clustering were found on the MMC side. Mechanical testing demonstrated that high quality dissimilar joints, characterized by good tensile and fatigue properties, with respect to the AA2024 base material, were obtained by means of LFW. Fracture was usually located in the weld center or in the thermo-mechanically affected zone (TMAZ), due to the plastic flow which the material underwent during the solid state welding process.