Phase stability and transformations in NiTi from density functional theory calculations
Abstract
We used density functional theory to characterize various crystalline phases of NiTi alloys: (i) high-temperature austenite phase B2; (ii) orthorhombic B19; (iii) the monoclinic martensite phase B19'; and (iv) a body-centered orthorhombic phase (BCO), theoretically predicted to be the ground state. We also investigated possible transition pathways between the various phases and the energetics involved. We found B19 to be metastable with a 1 meV energy barrier separating it from B19. Interestingly, we predicted a new phase of NiTi, denoted B19 '', that is involved in the transition between B19' and BCO. B19 '' is monoclinic and can exhibit shape memory; furthermore, its presence reduces the internal stress required to stabilize the experimentally observed B19' structure, and it consequently plays a key role in NiTi's properties.
Keywords
SHAPE-MEMORY ALLOYS; MINIMUM ENERGY PATHS; ELASTIC BAND METHOD; MARTENSITIC TRANSFORMATIONS; MOLECULAR-DYNAMICS; CRYSTAL-STRUCTURE; SADDLE-POINTS; TI ALLOY; TRANSITION; SYMMETRY
Date of this Version
2-2010
Recommended Citation
Vishnu, Karthik Guda and Strachan, Alejandro, "Phase stability and transformations in NiTi from density functional theory calculations" (2010). Birck and NCN Publications. Paper 592.
https://docs.lib.purdue.edu/nanopub/592