Influence of prestraining on cyclic deformation behaviour and microstructure of a single-phase Ni-base superalloy

Abstract

The influence of a monotonic predeformation at room temperature on the cyclic deformation behaviour of single-phase Ni-base superalloy Nimonic 75 was studied at various plastic strain amplitudes and temperatures from room temperature to 800°C. For all test parameters, Nimonic 75 shows a pronounced cyclic saturation behaviour. At intermediate temperatures, dynamic strain ageing effects occur. The planar slip character observed was found to prevail under all test conditions applied and leads to a cyclic stress–strain curve, which is rather independent of the testing mode used (single step test, multiple step test, incremental step test). Predeformation leads to a characteristic change in the dislocation arrangement and affects cyclic stress–strain response. In general, the influence of a predeformation on the macroscopic mechanical behaviour and the microstructure of Nimonic 75 decreases with increasing temperature and increasing loading amplitude.