Micromechanism of Propagation of Fatigue Cracks in Pseudoelastic NiTi Shape-Memory Alloy

• Published in: Materials science (New York, N.Y.) Vol. 56; no. 4; pp. 461 - 465
• Main Authors: Yasnii, V. P., Student, O. Z., Yasnii, P. V., Nykyforchyn, H. М.
• Format: Journal Article
• Language: English
• Published: New York Springer US 2021; Springer; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Crack propagation; Crack tips; Cracks; Cyclic loads; Fatigue cracks; Fatigue failure; Martensite; Martensitic transformations; Materials Science; Nickel alloys; Nickel base alloys; Nickel titanides; Nitinol alloys; Shape effects; Shape memory alloys; Solid Mechanics; Stress intensity factors; Stress ratio; Structural Materials; pseudoelastic NiTi alloy; micromechanism of crack growth; fatigue crack growth; stress ratio in a loading cycle
• ISSN: 1068-820X; 1573-885X
• DOI: 10.1007/s11003-021-00451-3

We analyze the kinetic features and micromechanism of propagation of fatigue cracks in pseudoelastic nitinol alloy with shape-memory effect under the conditions of constant-amplitude cyclic loading with stress ratios
R
= 0.2 and 0.5. It is established that, independently of the parameter
R
, fatigue cracks grow by the quasicleavage mechanism, which is explained by the austenite-martensite deformation transformation at the crack tip. This also explains the fact that the maximal value of the stress intensity factor in a loading cycle (but not its range) is responsible for the kinetics of fracture observed as the stress ratio
R
changes.