Influence of thermomechanical treatment on grain growth in the γ-rich nickel-base ODS superalloy PM3030

The mechanisms of secondary recrystallization and texture development during annealing of extruded PM3030, an oxide-dispersion-strengthened γ'-rich Ni-base superalloy, were investigated. For this purpose the material was heat treated or subjected to thermomechanical treatment. The occurrence of discontinuous grain growth during a high-temperature anneal was found to be affected by the dimensions of the extruded bar as well as by hot rolling or preannealing. We propose to attribute this behaviour to the mobility of triple junctions owing to the fine grain size. The appearance of a sharp <110> fiber texture was associated with the extruded microstructure. The preferred <111> direction occurred independent of the direction of the temperature gradient. The abnormal grain coarsening in this alloy is possibly promoted by local differences in γ' dissolution, but the influence of an inhomogeneous particle dispersion or even oriented growth on grain growth and texture development could be ruled out. (orig.)