Dislocation configurations in two phase TiAl alloys. II. Structures after compression

Abstract

Deformation microstructures produced by compression on the alloys Ti-48Al and Ti-47.5Al 2.5Cr have been analysed and compared to those obtained by hardness indentations of the same materials in Part I of this study. It is shown that while most of the strain in the indented specimens was achieved by glide of 1/2<110] dislocations, an important part of the deformation process occurs by twinning during compression. Also, other contributions from different active systems are observed that depend on the orientation relationships between the different grains. Both alloys contain single 1/2<110] dislocations, however the superdislocations present in the binary alloy are of the <101] type while the chromium containing alloy deforms by 1/2<112] segments that trail faulted dipoles. The dissociations of the <101] segments observed in the binary alloy seem to depend on the orientation of the line direction. The slightly better ductility of the chromium containing alloy has been attributed to the increased capacity of the α2/γ interface to accumulate dislocations prior to crack formation.