Low-cycle fatigue and microstructure of Cu–Fe single crystals with a double-slip orientation

Low-cycle fatigue behavior of [1 1 3] double-slip oriented Cu–Fe alloy single crystals with and without precipitated f.c.c. γ-Fe particles were examined under plastic-strain-controlled fatigue tests and compared with that of single-slip oriented crystals such as [4 1 9]. Although the γ-Fe particles are coherent and shearable, no cyclic softening was observed in all the particle bearing specimens. The cyclic stress–strain curves of the [1 1 3] crystals show a plateau region similar to those in the [4 1 9] crystals. On the other hand, shear stress amplitude increased monotonically with increase in shear strain amplitude on solution treated specimens. Dislocation microstructures characteristic of cyclic deformation were more clearly developed in the [1 1 3] crystals. Magnetic measurement of fatigued specimens revealed that more particles had transformed martensitically into b.c.c. α-Fe in the [1 1 3] crystals than in the [4 1 9] crystals. The above results can be understood reasonably if orientation-dependent deformation and transformation characteristics are taken into account.