Environmental Fatigue of 7075-T6 Aluminum Alloy

Abstract

The fatigue lifetime of the aluminum alloy 7075-6 depends upon the cyclic stress amplitude and the environment. At an R value of 0.05, and a maximum stress of 400 MPa the lifetime in vacuum is an order of magnitude greater than that in air, but interestingly at a maximum stress of 275 MPa, the lifetime in vacuum is only three times that in air. It was noted that well defined striations were observed in air, whereas striations were absent in vacuum, instead indications of ductile rupture were observed. The mechanism of fatigue crack initiation and propagation behavior as influenced by the environment is discussed.