Influence of Precorrosion on Fatigue Properties of Shot-Peened Aluminium 7075-T651

Abstract

Pitting corrosion has a major influence on aging of structural elements made of high-strength aluminium alloys as corrosion pits lead to much earlier fatigue crack initiation under tensile dynamic loading. In order to improve material resistance to corrosion fatigue, it is necessary to reduce pit-tip stresses in the corroded pits areas. Shot peening (SP) is an important and well-known cold working process, having been used in industrial applications for a long time. Shot peening as intense plastic deformation in the thin surface layer affects cold surface hardening by primary inducing favorable residual compressive stresses. It is used in order to increase fatigue strength in operation and to improve fatigue resistance of precorroded material. The paper deals with the surface integrity of shot-peened high-strength 7075-T651 aluminium alloy. The paper describes the effects of SP treatment by presenting analyses of surface roughness measurement, residual stresses, material bending fatigue resistance, fractographic analysis of fatigued specimens, and electrochemical potentiodynamic testing.