Corrosion and Fatigue of AL-Alloys AA359.0 and AA6060 in Different Surface Treatment States

Abstract

The consequences of near surface materials properties and residual stress states produced by specific manufacturing operations on damage evolution during corrosion fatigue of the Al-base alloys AA359.0 (German grade G-AlSi9Cu3) and AA6060 (German grade AlMgSi0.5) were systematically investigated. Specimens were processed applying mechanical surface treatments like shot peening or deep rolling and investigated in comparison with turned states. Surface topographies as well as near surface work hardening states and residual stress depth distributions were analyzed. Tension-compression fatigue tests were carried out under laboratory air as well as under salt spray test conditions or in salt solution. Crack formation and crack propagation was studied and characteristic examples are presented. The influence of the mechanical surface treatments on the electrochemical behavior was also investigated. To assess the consequences of near surface materials properties on the corrosion fatigue behavior, their stability during fatigue, in particular the relaxation of residual stress distributions introduced by mechanical surface treatments, was taken into account.