A Contribution to the Study of the Plastic of α Iron and B.C.C. Alloys by the Determination and Analysis of Creep Data

Abstract

In the range of temperature 220-300 K, we have studied the plastic microstrain of a iron by torsional creep test using thin tubes. According to the applied stress we have determined three types of creep. For small stress, the first type can be represented by Friedel's model of microcreep. In the second one, the deviation from logarithmic law seems to be due to a non linear evolution of internal stress with creep deformation. Supposing that the field of internal stress is created by dislocations locked at insurmountable obstacle, probably at grain boundary, it is possible to determine the parameter m, appearing in the power law: V = Kσmeff, through the analysis of the creep curves. Thesevalues which were found agree with lit erature. In the second part, the method applied to the case of two tempered steels shows a behaviour similar to that of iron provided it is assumed that dislocations are locked on precipitates of Fe3C.