Study the thermal fatigue behaviour and electric property of AA7025 by ultrasonic impact peening (UIP)

Abstract

The fatigue life and strength of a peened component is a compromise between two opposing effects, the creation of a compressive residual stresses (CRS) resulted in increasing the life and strength, countered in part by initiation of crack which tend to reduce the life and strength. In recent years, aluminum alloys have emerged particularly in the industry, i-e in the conditions of thermal fatigue such as, crank shaft, piston, and aircraft engine due to a significant weight savings with no loss of properties. The ultrasonic impact peening (UIP) technique is widely utilized to produces plastic deformation of the surface, leading to the creation of (CRS). Fatigue S – N curve are obtained for four cases of testing As – received (AR), (AR + UIP), elevated temperature (ET) and (UIP + ET) for AA7025. It is deduced that the fatigue life and strength of AA7025 improved due to application of (UIP). However, the fatigue life and strength were increased by (UIP) as a result of generating of (CRS), Also the electrical properties were studied and it was concluded that the (UIP) reduce the above properties and it was understood that the electrical conductivity increased with increase the frequency.