The effect of vacancies on the environmental yield strength dependence of boron-free and boron-doped Fe-40Al

The effect of environment on the yield strength of boron-free and boron-doped Fe-40Al was considered. Special attention was given to the role of excess thermal vacancies. It was found that samples given a vacancy-relieving heat treatment had a 12% lower yield strength when tested in air than when tested in vacuum. This was attributed to an environmental softening effect. However, samples with a large amount of quenched-in vacancies exhibited no environmental yield strength dependence. These observations were found in both the boron-free and boron-doped alloys.