On the evolution of internal stresses and glide resistance during Bauschinger tests performed on a γ(TiAl) alloy

Abstract

Bauschinger tests performed on a γ(TiAl) alloy exhibit transient softening. Reversal of the strain path leads to a sharp drop in the yield stress, which then rises again to almost the value of non-predeformed specimens [1]. The present paper provides new data that may elucidate the phenomenon. The internal stress was measured by dip tests along the strain path involving (forward) compression and (backward) tension. In addition, the dislocation glide resistance was characterized by stress relaxation tests. Accordingly, the flow behaviour during the Bauschinger test is determined by the development of an internal stress field during forward compression, which upon strain reversal is inverted and then supports backward tension. At the same time, the dislocation glide resistance is significantly reduced. This behaviour is explained using literature on deformation processes in TiAl alloys.