Optimization of Microstructure and Mechanical Properties of 2219 Al Alloy Cold-Sprayed Coating by Heat Treatment

This study investigates the influence of different heat treatment processes on the microstructure and mechanical properties of cold spraying coatings deposited on TIG joints of 2219 Al alloy. The results indicate that there were no significant changes in the microstructure of the joint before and after cold spraying. However, there was noticeable plastic deformation at the interface between the joint and the coating. The porosity rates of coatings subjected to room temperature, direct aging, and solution aging are 1.94%, 0.67%, and 4.57%, respectively. After direct aging, the extent of plastic deformation in the coating decreases. Following solution aging, recrystallization occurs in the coating leading to grain growth. A comparison of the microstructures of the three types of coatings revealed a gradual reduction in dislocation density and the quantity of low angle grain boundaries (LAGBs) within the coatings. Following solution aging, a significant amount of needle-like long-period transition phase θ′ precipitated. The coating hardness transitioned from a step-like distribution to a more uniform distribution, with an approximate 5HV increase in hardness within 2.5mm depth from the surface of the substrate. The tensile strength of joints with coatings improved by 5.6% and 30.9%, respectively, while the elongation increased by 15.4% and 93.3%, resulting in significantly enhanced ductility. The coating fracture mode transitions from predominantly brittle fracture to primarily ductile fracture.