Some effects of martensitic transformation on fatigue resistance

Some fatigue phenomena are discussed, which are because of diffusionless transformation of metastable metallic phases. The following aspects are relevant to high-cycle fatigue resistance: (i) crystallographic reversibility (shape memory alloys, SMA), or irreversibility, with change in volume (austenitic steels) of the martensitic transformation; (ii) mechanical, thermal, thermomechanical cycling; (iii) effects on crack nucleation or growth because of the structural instability; and (iv) fatigue of functional properties (shape memory, transformation temperatures). Micromechanical models are proposed in order to define the conditions for considerable retardation of crack initiation and early stages of crack growth. Special aspects as the role of heat flow (SMA) or localized formation of a ferromagnetic phase at the crack tip (steels) are discussed briefly.