Effect of Shot Peening and Heat Treatment on Fatigue Strength and Microstructure of Stir Casted Al7075-SiC Composites

Abstract

Aluminium matrix composites are analyzed by many researches already to improve the properties such as wear, hardness, tensile and compressive strengths in order to use it for automobile, aircraft and other applications. Limited attempts were taken to improve the cyclic load carrying capacity of these materials. The present study focuses on improving the fatigue strength of Al7075 composite reinforced with SiC particles. 8 vol.% of SiC is used as reinforcement to produce composite specimens. Stir casting, an economic and best chosen method, is employed to produce composite samples. A portion of the casted samples are machined to ASTM standards and heat treated to T6 conditions. Shot peening is carried out using steel shots on some of the heat treated and non-heat treated composite specimens. Almen strip test is conducted earlier to predict the peening time. High cycle fatigue tests are conducted on heat treated shot peened samples and are compared with Al7075 and composites at as cast, heat treated non-shot peened and shot peened non-heat treated conditions. Improvement of around 6% is found for heat treated shot peened samples than that of Al7075. Microstructural analysis revealed the surface modifications because of shot peening and heat treatment.