Premartensite Transformation in Ni(50.5)Ti(49.5)
Abstract
Small deviations from stoichiometry in the thermoelastic NiTi martensitic alloy yield sufficiently large separation of the martensite and premartensite transformations to allow a thermal analysis study of the premartensite transformation without the complication of competing phenomena. The nature of the premartensite transformation in Ni50.5Ti49.5 and its relation to similar phenomena in stoichiometric and iron-doped NiTi is the subject of the present report. Data indicate that the premartensite transformation width in Ni50.5Ti49.5 is due to a distribution of regions of the sample that transform from the cubic to the rhombohedrally distorted CsC1 phase over a range of temperatures, and these regions transform back to cubic CsC1 structure in reverse order upon reheating. In contrast to the results in iron-doped NiTi, no evidence of a two-step transformation could be found in a series of studies of the metastability and transformation kinetics of mixtures of phases produced by partially transforming from the pure CsC1 phase and from the pure rhombohedrally distorted CsC1 phase. Keywords: Shape memory alloys, Titanium alloys, Nickel alloys, Martensite transformations, Differential scanning calorimetry.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1988
- Accession Number
- ADA197458
Entities
People
- Lawrence V. Meisel
- Paul J. Cote
Organizations
- United States Army Armament Research, Development and Engineering Center