Investigation on APBs and dissociation of super dislocations in TiAl by APFIM

Abstract

The atomic stacking sequence along the 〈001〉 direction in γ-TiAl (L1₀ type of structure) of an as-cast two phase TiAl/Ti₃Al intermetallic alloy with Cr and Si additions has been investigated by field ion microscopy (FIM) and supported atom probe microanalysis. The γ-phase possesses a high degree of ordering. During cooling thermally formed (100) antiphase boundaries (APBs), super dislocations, as well as super partial dislocations were observed and detected by APFIM. From this it is suggested that the addition of Cr lowers the APB energy in TiAl and the origin of the APBs is related to the displacement of 1/2〈011〉 super partial dislocations.