Intermediate temperature stress anomaly in B2 alloys: with special attention to the case of iron aluminides

摘要

The iron aluminides show anomalous stress peaks at temperatures of the order of 400～600°C, irrespective of whether the crystal structure is B{sub}2 type or DO{sub}3 type. Such features will be examined on the basis of thermally-activated dislocation processes, considering the influence of test parameters such as temperature and strain rate, and material parameters such as crystal composition and orientation. Detailed analyses of deformation modes by slip step studies, transmission electron microscopy examinations of dislocation structures, and texture studies will also be considered. Observations of dislocation structures are clearly of great interest for suggesting the possible models of deformation, but suffer from two major weaknesses: the post-mortem structures in samples deformed at high temperature may not be the same as those producing plasticity; almost all possible hypotheses for strengthening can find support from such observations, since almost all imaginable dislocation configurations can be found with sufficient diligence by the researcher. Strengthening at intermediate temperatures in DO{sub}3 and B{sub}2 ordered iron aluminides will be analyzed here, making combined use of observations of deformation structures and examinations of the influence of varying the deformation parameters.