Microstructure and mechanical properties of as-cast quasibinary NiTi-Nb eutectic alloy

C. Bewerse, L. C. Brinson, D. C. Dunand*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Ni40Ti40Nb20 is reported in the literature as a eutectic composition in the quasi-binary NiTi-Nb system. Eutectic and near-eutectic alloys find applications in various fields, including hydrogen permeation, energy damping, and liquid phase bonding of NiTi structures. In this study, we examine a cast Ni-Ti-Nb alloy with the above eutectic composition. Prealloyed, near-stoichiometric NiTi powders and pure Nb powders are blended and heated above the eutectic temperature to create a melt with the eutectic composition. After solidification, the ingot shows some elemental segregation at its top and bottom, but a large middle region exists with a homogeneous eutectic structure. The eutectic has average composition of Ti-40.1Ni-19.6Nbat% and consists of Nb-rich lamellae (Nb-19Ti-10Ni) dispersed within a NiTi-rich matrix (Ti-41Ni-15Nb). Under monotonic compressive deformation, the eutectic alloy yields at 630MPa, and then shows a linear hardening region, where both plastic and superplastic deformation are active, until a stress of 1080MPa is reached at an applied strain of 14.7%. On unloading, some superelastic strain is recovered. Upon unloading during compressive load-unload cycling, the eutectic alloy exhibits approximately twice as much superelastic recovery as elastic strain recovery, regardless of the maximum cycle strain.

Original languageEnglish (US)
Pages (from-to)360-368
Number of pages9
JournalMaterials Science and Engineering A
Volume627
DOIs
StatePublished - Mar 1 2015

Keywords

  • Eutectic
  • Liquid phase sintering
  • NiTi
  • Shape memory alloy
  • Superelastic

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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