The non-monotonic temperature dependence of the yield stress in TiAl and CuAu alloys

An anomalous temperature dependence of the yield stress in the ordered CuAu alloy was detected. Blocked <101] superdislocations were observed in the region of the anomalous trend from room temperature to 300 degrees C. Blocking of single dislocations was not detected at these temperatures. The comparison with the known data on the TiAl intermetallic was carried on. The causes of the nonmonotonous temperature dependence of the yield stress with two extremum points were analyzed. The set of possible states of dislocations in TiAl was discussed. A unified scheme with account of mutual dislocation transitions was proposed for the description of the deformation behavior over the whole temperature interval. Specific features of the dislocation structure of CuAu and TiAl were explained. The connection between the brittleness of TiAl and dislocation transformations was discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.