Fatigue crack initiation and propagation of a TiNi shape memory alloy

In this paper, fatigue crack initiation and the propagation stages of a TiNi shape memory alloy are examined using a low cycle fatigue interrupted test. Submitted to fatigue cyclic loading, the response of the alloy presents a classical pseudoelastic response. Two potential initiation crack areas are highlighted: at the phase interfaces and at the grain boundaries. Propagation results from the coalescence of many microscopic cracks. These two stages are detectable in the last 20% of the total fatigue life.