Self-assembling behavior of supersaturated thermal vacancies in FeAl single-crystal

In FeAl, the effects of supersaturated thermal vacancies, their self-assembling on nano- to micro-structures, and their mechanical properties, are significant. In this study, the self-assembling behavior of supersaturated thermal vacancies was investigated with single-crystals using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). An irreversible exothermic peak was detected in as-quenched crystals by DSC. Isochronal changes of surface morphology and substructure around the exothermic peak temperature were observed by TEM. The average size of the surface pores increased uniformly with increasing temperature. Dislocations whose Burgers vectors were parallel to 〈1 0 0〉 existed in the isochronally heated crystals and their density varied with temperature. However, there was a dislocation-free zone extending from the surface to a depth of several tens of nanometers, indicating that supersaturated thermal vacancies in this zone were completely exhausted to form surface pores. A growth model of the surface pores is discussed based on the results.