Experimental investigation of the effects of aging and cryogenic treatments on the mechanical properties of superelastic nickel-titanium shape-memory alloys


Güven S., Altin Karataş M., Gökkaya H., Akınay Y.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, vol.236, no.12, pp.6752-6759, 2022 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 236 Issue: 12
  • Publication Date: 2022
  • Doi Number: 10.1177/09544062211069864
  • Journal Name: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, Applied Science & Technology Source, Communication Abstracts, Compendex, INSPEC, Metadex, Civil Engineering Abstracts
  • Page Numbers: pp.6752-6759
  • Keywords: Smart materials, shape-memory alloys, mechanical properties, cryogenic treatment, aging, MULTISTAGE MARTENSITIC-TRANSFORMATION, SMART MATERIALS, MICROSTRUCTURE, BEHAVIOR
  • Van Yüzüncü Yıl University Affiliated: Yes

Abstract

© The Author(s) 2022.In this study, electropolishing and two different heat treatments were applied to wires made of superelastic nickel-titanium (NiTi) shape-memory alloy (SMA) and their mechanical properties and stress-induced deformations were investigated. In experimental studies, cryogenic and aging heat treatments were applied to NiTi SMA wire samples and tensile test experiments were carried out to determine the effect of the heat treatments on their mechanical properties. Following the tensile test experiments conducted at room temperature (23°C), the study investigated changes in the elemental composition, fracture modes, micro cracks, and phase structures and in the mechanical properties formed in the fracture region. Intermetallic phase structures (Ti2Ni, Ni3Ti, and Ni4Ti3) were observed in the X-ray diffraction (XRD) analyses. It was concluded that the aging heat treatment had directly affected the reduction in hardness. In particular, in samples without the aging heat treatment, a stress-induced decrease in the Ni and Ti ratios and an increase in the carbon (C) ratio were observed in the chemical composition of the fracture surface of the superelastic NiTi SMA wires. It was determined that the changes in the chemical composition caused by stress had affected the mechanical properties negatively. In the fractography of the NiTi SMA wires, the samples exhibited mostly ductile fracture behavior with small dimples.