Effects of Stresses on the Phase Transformation of NITINOL
Abstract
Sequential annealing treatments up to 400 C were performed on a severely cold wrought nickel rich Nickel Titanium (NITINOL) alloy to demonstrate the shape memory performance of the alloy as a function of annealing. The strain recovery was 2.75%. The electrical resistance responses associated with the phase transformations of the specimen, subsequent to the various annealing treatments, are shown and interpreted. Supporting data were obtained on the same alloy for varied annealing cycles by use of a differential scanning calorimeter. Both residual and precipitation-associated stresses have a marked effect on electrical resistance and calorimetric responses during the phase transformation. The changed responses provide the basis for considering the transformation to occur via a metastable rhombohedral (R) structure. The extent to which the R may exist is shown to be related to the residual stresses. The stresses also have a significant effect on the shape memory response. The substantial changes in the range of transition temperatures which can be obtained by various annealing treatments of this slightly nickel rich NITINOL are tabulated. (Keywords: Nickel Alloys, Titanium Alloys).
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 02, 1986
- Accession Number
- ADA177053
Entities
People
- David M. Goldstein
- John Tydings
- Lawrence T. Kabacoff
Organizations
- Naval Ordnance Laboratory