Investigation of Flexural Strength and Surface Hardness in Aluminum 2024-T3 Subjected to Shot Peening Process by Ni Shots

Abstract

Innovations in finding new materials and material processing methods are important to improve the working life of components. Refinement of surface microstructure improves the overall performance of components (Singh et al. in Trans Indian Inst Met 69:295, 2016). This research paper aims to enhance the flexural strength and hardness of aluminum alloy 2024-T3 by imparting surface residual compressive stress using shot peening technique using nickel shots. The compressive stress layer imparted by shot peening technique is found to modify the existing microstructure in AA2024-T3 specimens. Shot peening is carried out using compressed air in a nozzle with pressure ranging from 0.4 to 0.6 MPa and nozzle to target distance ranging from 30 to 60 mm. Combinations of pressure and distance for performing experiments are obtained using response surface methodology (RSM). Based on the obtained combinations, experiments are performed. Flexural strength and surface hardness are found from tests. Optimized parameter values for maximum response are arrived using RSM, and confirmation experiments are done with optimized parameter values. The experiments prove that the flexural strength and hardness values are found to be more than 95% close to predicted values. FESEM test results for specimens peened with optimal parameters, show the presence of nickel in the specimen surface. Shot peening results in alloying of nickel with base material, and thus show the flexural strength and surface hardness improved by 8.80% and 29.7%, respectively. A comparative study is also done on AA2024-T3 specimens before and after shot peening with nickel shots. Test results show a significant hike in flexural strength and surface hardness in AA2024-T3 when shot peened with nickel shots.