TY - JOUR
T1 - Crystallography of the B2 → R → B19′ phase transformations in NiTi
AU - Zhang, Xiangyang
AU - Sehitoglu, Huseyin
N1 - Funding Information:
The research is supported partially by the National Science Foundation, CMS 99-00090, Mechanics and Materials Program, Arlington, Virginia, and the Air Force Office of Scientific Research, Arlington, Virginia.
PY - 2004/6/15
Y1 - 2004/6/15
N2 - The crystallography of B2 to R-phase and the subsequent R-phase to B19′ martensite transitions was analysed in NiTi alloys. Using the energy minimization theory of martensitic transformations, the habit plane and twin plane normals were established for the R-phase, B19′ martensite variants as a function of rhombohedral angle α. Two types of twins, classified as {100}〈011〉 and {0}〈001〉 compound twins could form in the R-phase. There are 12 R-phase variants with {10}〈0 0 1〉 compound twins when α<90°. When α>90° there are 24 R-phase variants with {100}〈01 1〉 compound twins and 12 variants with {1〈0 1〉 compound twins, respectively. In total, eight possible twins can be formed in B19′ martensite. In the single step B2 to B19′ martensitic transformation, only four twin types are qualified as lattice invariant shear (LIS); while all the eight twin types are qualified as LIS in R-phase to B19′ transition the {1 0 0}〈0 1 1〉 compound, {10}〈0 1〉 compound and {11̄0}〈1 1 2.7008〉 Type I twins have been observed in the experiments. The results indicate that the premartensitic R-phase transition plays an important role in understanding the phase transformations in NiTi shape memory alloys.
AB - The crystallography of B2 to R-phase and the subsequent R-phase to B19′ martensite transitions was analysed in NiTi alloys. Using the energy minimization theory of martensitic transformations, the habit plane and twin plane normals were established for the R-phase, B19′ martensite variants as a function of rhombohedral angle α. Two types of twins, classified as {100}〈011〉 and {0}〈001〉 compound twins could form in the R-phase. There are 12 R-phase variants with {10}〈0 0 1〉 compound twins when α<90°. When α>90° there are 24 R-phase variants with {100}〈01 1〉 compound twins and 12 variants with {1〈0 1〉 compound twins, respectively. In total, eight possible twins can be formed in B19′ martensite. In the single step B2 to B19′ martensitic transformation, only four twin types are qualified as lattice invariant shear (LIS); while all the eight twin types are qualified as LIS in R-phase to B19′ transition the {1 0 0}〈0 1 1〉 compound, {10}〈0 1〉 compound and {11̄0}〈1 1 2.7008〉 Type I twins have been observed in the experiments. The results indicate that the premartensitic R-phase transition plays an important role in understanding the phase transformations in NiTi shape memory alloys.
KW - NiTi alloys
KW - R-phase transition
KW - Shape memory
KW - Two-step phase transformations
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U2 - 10.1016/j.msea.2004.03.013
DO - 10.1016/j.msea.2004.03.013
M3 - Article
AN - SCOPUS:2642557149
VL - 374
SP - 292
EP - 302
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
SN - 0921-5093
IS - 1-2
ER -