Environmental embrittlement of Al–Sn alloys and its implication for fatigue crack growth

Abstract

The environmental embrittlement of a series of Al–Sn alloys has been studied using the technique of slow strain rate testing in laboratory air, in a packing of anhydrous magnesium perchlorate, and in a salt solution (2%NaCl–0·5%Na₂CrO₄ buffered to pH 3·5). The embrittlement occurring at slow strain rates is attributed to reversible hydrogen embrittlement. Only the alloy containing a continuous network of tin phase suffers a reduction in ductility. This is attributed to an increase in hydrogen diffusivity which is demonstrated through a series of permeation tests. These results are then used to interpret fatigue crack growth tests conducted as a function of environment in the absence of closure.

MST/744