Tension-Compression Asymmetry in gamma-TiAl Single Crystals

摘要

Single crystalline microsamples of Ti-55.5percentAl have been tested in tension at temperatures ranging from 873K to 1173K. The results of these tensile experiments have been compared with previously reported values of the compressive strength of this material, and a tension-compression (T/C) asymmetry has been observed for three different orientations. This T/C asymmetry has been related to the dissociation and motion of superdislocations and it has been shown that the flow strength is a maximum when the superdislocations are led by the SISF dissociated superpartial and a minimum when they move with a leading CSF superpartial. This finding and further consideration of the crystal geometry suggest that the formation of roof-type barriers is most favorable when the applied stress promotes cross-slip of the trailing CSF dissociated superpartial dislocation.