Effect of multiple laser shock peening on mechanical properties of aluminum alloy 2014-T6

Laser shock peening is a surface optimization operation that leads to the improvement of mechanical properties such as increasing fatigue strength, surface hardness and tensile strength. This improvement of properties can be attributed to the creation of residual stress and cold work done on the surface. In this new method, which is considered as an alternative to the methods of peening and ultrasonic peening waves, there are many influential factors such as power density, percentage of overlap, type of protective layer and number of shocks, etc. In this research, Al2014-T6 alloy, which is widely used in aviation industries, including aircraft wheels, has been subjected to shock peening in order to increase its strength and fatigue life. Single, triple and quintuple shock processes were applied on this alloy to investigate the effect of different shock modes. Next, the amount of residual stress was analyzed with the help of X-ray diffraction analysis and changes in surface roughness by atomic force microscope, and then fatigue, tensile and microhardness tests were performed on the part. The results of the experiments show that with the increase in the number of times of laser shock and under the condition of no melting and surface destruction, the residual compressive stress increases, which leads to a 300% increase in fatigue life and a 25% increase in microhardness of the surface. It was also found that in addition to optimizing the parameters, increasing the shock frequency can also change the surface roughness and tensile strength.