SOME ASPECTS OF THERMOMECHANICAL FATIGUE OF AISI-304L STAINLESS-STEEL.2. DISLOCATION ARRANGEMENTS

The influence of plastic strain rate, plastic strain amplitude, and te mperature interval on the dislocation arrangements which are formed du ring thermomechanical fatigue (TMF) of the austenitic stainless steel AISI 304L in ''true'' plastic-strain control have been investigated. A t temperatures below the creep regime and/or at high-plastic strain ra tes, a typical dislocation arrangement called the layer/wall structure has been observed. It can be regarded to be a consequence of impeded dynamic recovery, whereby the lack of creep processes and the occurren ce of dynamic strain aging contribute to the formation of this structu re. With increasing temperature and decreasing strain rate, a transiti on takes place to subgrain-type microstructures as a result of enhance d creep-fatigue interaction. The influence of various parameters on th e developing dislocation arrangements is discussed and summarized in a dislocation map.