Fatigue Properties Associated with Cyclic β₁\ ightleftarrowsβ₁′ Transformation Pseudoelasticity of Cu–Al–Ni Alloy Single Crystals

抄録

The fatigue properties associated with the β₁\ ightleftarrowsβ₁′ transformation pseudoelasticity cycling of Cu–Al–Ni alloy single crystals have been investigated by cyclic loading tests and fractographic observations. Fatigue life is surprisingly short even under 100 MPa of applied stress, although the static fracture stress is as high as 650 MPa, and it is insensitive to applied stress in carefully electropolished specimens. Various factors affecting the fatigue properties, such as specimen orientation, applied stress, stress amplitude, amount of transformation strain and quenching rate from the matrix phase, have been examined. Fractographic observations and two-surface analyses of fracture surfaces show that the fatigue fracture is a brittle type except for the initial stage of the formation of crack nuclei. It is suggested that the essential cause of low fatigue life of Cu–Al–Ni alloys is in the low fracture toughness of the alloy itself and in some defect formation, which leads to crack nuclei, at martensite-matrix interfaces during β₁\ ightleftarrowsβ₁′ transformation pseudoelasticity cycles.