A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 1 6 0 Shape Memory and Superelasticity: Advances in Science and Technology (SMJ) is the official journal of the International Organization on Shape Memory and Superelastic Technologies (SMST), an affiliate society of ASM International. The journal publishes original peer-reviewed papers that focus on shape memory materials research with contributions frommaterials science, experimental and theoretical mechanics, physics with cognizance of the chemistry, underlying phases, and crystallography. It also provides a forum for researchers, scientists, and engineers of varied disciplines to access information about shape memory materials. Three articles were taken from the September 2020 issue and one is from the March 2021 issue. All were selected by Shape Memory Editor-in-Chief Huseyin Sehitoglu. SMJ is available through springerlink.com. For more information, visit asminternational.org/web/smst. FATIGUE CRACK INITIATION IN THE IRON-BASED SHAPE MEMORY ALLOY FeMnAlNiTi R. Sidharth, W. Abuzaid, M. Vollmer, T. Niendorf, and H. Sehitoglu The newly developed FeMnAlNiTi shape memory alloy (SMA) holds significant promise due to its desirable properties including ease of processing, room temperature superelasticity, a wide superelastic window of operation, and high transformation stress levels. In this study, we report single crystals with tensile axis near <123> exhibiting transformation strains of 9% with a high transformation stress of 700 MPa. The functional performance revealed excellent recovery of 98% of the applied strain in an incremental strain test for each of the 40 applied cycles. Concomitantly, the total residual strain increased after each cycle. Accumulation of residual martensite is observed possibly due to pinning of austenite/martensite (A/M) interface. Subsequently, under structural fatigue loading with a constant strain amplitude of 1%, the recoverable strains saturate around 1.15% in local residual martensite domains. Intermittent enhancement of recoverable strains is observed due to transformation triggered in previously untransformed domains. Eventually, fatigue failure occurred after 2046 cycles and the dominant mechanism for failure was microcrack initiation and coalescence along the A/M interface. Thus, it is concluded that interfacial dislocations, which play a crucial role in the superelastic (SE) functionality, invariably affect the structural fatigue performance by acting as the weakest link in the microstructure (Fig. 1). PSEUDOELASTIC NITINOL IN ORTHOPAEDIC APPLICATIONS David Safranski, Kenneth Dupont, and Ken Gall Pseudoelastic Nitinol presents an attractive material option for devices used in clinical orthopaedic applications. The capacity of the material to exert sustained compression during shape recovery aligns well with the mechanobiological factors associated with bone healing, particularly in SMJ HIGHLIGHTS Fig. 1 — SEM-BSE image of the sample surface post-fatigue fracture. The low-magnification image on the right shows the residual martensite near the fatigue crack. The fatigue crack has propagated parallel to the activated martensite variant. A high-magnification image of the other fatigue cracks near the sample edge taken at 35,000x is shown on the left. Several microcracks have formed along the A/M interface. 1 2
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