The crystal chemistry of martensite in NiTiHf shape memory alloys

Mehrdad Zarinejad; Yong Liu; Timothy J. White

doi:10.1016/j.intermet.2008.04.004

The crystal chemistry of martensite in NiTiHf shape memory alloys

Mehrdad Zarinejad, Yong Liu^*, Timothy J. White

^*Corresponding author for this work

Nanyang Technological University

Research output: Contribution to journal › Article › peer-review

57 Citations (Scopus)

Abstract

The crystal structure of martensite in NiTiHf shape memory alloys of compositional formulas Ni₅₀Ti_50-xHf_x, Ti₅₀Ni_50-xHf_x, and Ni_(100-x)/2Ti_(100-x)/2Hf_x (5 ≤ x ≤ 20) were studied. The monoclinic lattice parameters and angle were changed by introduction of larger Hf atoms into the NiTi crystal. The changes were related not only to larger atomic radius of Hf but also to its effect on bond lengths. At the same Hf content, Ti-rich alloys exhibited larger cell volumes than Ni-rich alloys. The equiatomic alloys showed smaller unit cell volumes than the other two groups possibly due to more isotropic bonding. Valence electron per atom (e_v/a) and valence electron concentration (e_v/e_t) of the alloys were found to influence the atomic bond lengths and unit cell dimensions. From the crystal structure refinement, Hf site preference and occupancy were determined. The similar tendency of Hf towards occupancy in Ni and Ti sites, results in its preference for available sites in the structure.

Original language	English
Pages (from-to)	876-883
Number of pages	8
Journal	Intermetallics
Volume	16
Issue number	7
DOIs	https://doi.org/10.1016/j.intermet.2008.04.004
Publication status	Published - Jul 2008
Externally published	Yes

ASJC Scopus Subject Areas

General Chemistry
Mechanics of Materials
Mechanical Engineering
Metals and Alloys
Materials Chemistry

Keywords

A. Intermetallics, miscellaneous
B. Crystal chemistry of intermetallics
D. Martensitic structure
D. Site occupancy
F. Diffraction

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10.1016/j.intermet.2008.04.004

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title = "The crystal chemistry of martensite in NiTiHf shape memory alloys",

abstract = "The crystal structure of martensite in NiTiHf shape memory alloys of compositional formulas Ni50Ti50-xHfx, Ti50Ni50-xHfx, and Ni(100-x)/2Ti(100-x)/2Hfx (5 ≤ x ≤ 20) were studied. The monoclinic lattice parameters and angle were changed by introduction of larger Hf atoms into the NiTi crystal. The changes were related not only to larger atomic radius of Hf but also to its effect on bond lengths. At the same Hf content, Ti-rich alloys exhibited larger cell volumes than Ni-rich alloys. The equiatomic alloys showed smaller unit cell volumes than the other two groups possibly due to more isotropic bonding. Valence electron per atom (ev/a) and valence electron concentration (ev/et) of the alloys were found to influence the atomic bond lengths and unit cell dimensions. From the crystal structure refinement, Hf site preference and occupancy were determined. The similar tendency of Hf towards occupancy in Ni and Ti sites, results in its preference for available sites in the structure.",

keywords = "A. Intermetallics, miscellaneous, B. Crystal chemistry of intermetallics, D. Martensitic structure, D. Site occupancy, F. Diffraction",

author = "Mehrdad Zarinejad and Yong Liu and White, \{Timothy J.\}",

year = "2008",

month = jul,

doi = "10.1016/j.intermet.2008.04.004",

language = "English",

volume = "16",

pages = "876--883",

journal = "Intermetallics",

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AU - Zarinejad, Mehrdad

AU - Liu, Yong

AU - White, Timothy J.

PY - 2008/7

Y1 - 2008/7

N2 - The crystal structure of martensite in NiTiHf shape memory alloys of compositional formulas Ni50Ti50-xHfx, Ti50Ni50-xHfx, and Ni(100-x)/2Ti(100-x)/2Hfx (5 ≤ x ≤ 20) were studied. The monoclinic lattice parameters and angle were changed by introduction of larger Hf atoms into the NiTi crystal. The changes were related not only to larger atomic radius of Hf but also to its effect on bond lengths. At the same Hf content, Ti-rich alloys exhibited larger cell volumes than Ni-rich alloys. The equiatomic alloys showed smaller unit cell volumes than the other two groups possibly due to more isotropic bonding. Valence electron per atom (ev/a) and valence electron concentration (ev/et) of the alloys were found to influence the atomic bond lengths and unit cell dimensions. From the crystal structure refinement, Hf site preference and occupancy were determined. The similar tendency of Hf towards occupancy in Ni and Ti sites, results in its preference for available sites in the structure.

AB - The crystal structure of martensite in NiTiHf shape memory alloys of compositional formulas Ni50Ti50-xHfx, Ti50Ni50-xHfx, and Ni(100-x)/2Ti(100-x)/2Hfx (5 ≤ x ≤ 20) were studied. The monoclinic lattice parameters and angle were changed by introduction of larger Hf atoms into the NiTi crystal. The changes were related not only to larger atomic radius of Hf but also to its effect on bond lengths. At the same Hf content, Ti-rich alloys exhibited larger cell volumes than Ni-rich alloys. The equiatomic alloys showed smaller unit cell volumes than the other two groups possibly due to more isotropic bonding. Valence electron per atom (ev/a) and valence electron concentration (ev/et) of the alloys were found to influence the atomic bond lengths and unit cell dimensions. From the crystal structure refinement, Hf site preference and occupancy were determined. The similar tendency of Hf towards occupancy in Ni and Ti sites, results in its preference for available sites in the structure.

KW - A. Intermetallics, miscellaneous

KW - B. Crystal chemistry of intermetallics

KW - D. Martensitic structure

KW - D. Site occupancy

KW - F. Diffraction

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JO - Intermetallics

JF - Intermetallics

IS - 7

ER -

The crystal chemistry of martensite in NiTiHf shape memory alloys

Abstract

ASJC Scopus Subject Areas

Keywords

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