Effect of hydrogen on the dynamic modulus of elasticity of gamma titanium aluminides

The purpose of this investigation is to study the effect that hydrogen has on the modulus of elasticity of gamma titanium aluminide using a non-destructive vibration technique. Individual specimens with standard dimensions were cut from a gamma titanium aluminide sheet and mounted in a specially designed jig. Each specimen was then subjected to hydrogen charging by means of an electrolytic process at a constant current for a predetermined amount of time for up to 24 cumulative hours. After the specimen was charged with hydrogen, the modulus of elasticity was determined using the vibration technique. It is concluded from the experimental data that hydrogen has a degrading effect on the modulus of elasticity of gamma TiAl. Different charging conditions yielded the same results, a drop in Young's Modulus varying from 4% to 6.4% depending on the current density. This deleterious effect of hydrogen when modeled analytically as composite structures consisting of various layers with different modulus of elasticity using the rule of mixture generated reliable data with an error of only 9%. The result of this study is significant in the proposed application of gamma titanium aluminide as a turbine material in hypersonic vehicles.