Energy landscape for martensitic phase transformation in shape memory NiTi

✍ Scribed by S. Kibey; H. Sehitoglu; D.D. Johnson

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 373 KB
• Volume: 57
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2008.12.008

✦ Synopsis

First-principles calculations are presented for parent B2 phase and martensitic B19 and B19 0 phases in NiTi. The results indicate that both B19 and B19 0 are energetically more stable than the parent B2 phase. By means of ab initio density functional theory, the complete distortion-shuffle energy landscape associated with B2 ? B19 transformation in NiTi is then determined. In addition to accounting for the Bain-type deformation through the Cauchy-Born rule, the study explicitly accounts for the shuffle displacements experienced by the internal ions in NiTi. The energy landscape allows the energy barrier associated with the B2 ? B19 transformation pathway to be identified. The results indicate that a barrier of 0.48 mRyd atom À1 (relative to the B2 phase) must be overcome to transform the parent B2 NiTi to orthorhombic B19 martensite.