An investigation on the crystal structures of Ti50Ni50−xCux shape memory alloys based on density functional theory calculations

Gou, Liangliang; Liu, Yong; Ng, Teng Yong

doi:10.1016/j.intermet.2014.04.013

Cited by 33 publications

(25 citation statements)

References 39 publications

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“…As the atomic radius of Cu is slightly smaller than that of Ni, the size mismatch is not significant, which is consistent with the previous observation that there is no dramatic change of crystal structure when substituting Cu in TiNiCu martensitic alloys [25]. Our earlier work noted that more electrons escape from the Ti atoms in comparison with the equiatomic TiNi binary alloy with increasing Cu content [25]. The more charge transfer between Ti and Ni/Cu atoms, the stronger the interaction between them will be, and the higher the bonding force between them is, leading to a shorter bond length.…”

Section: Resultssupporting

confidence: 91%

“…In Figure 5, the bond lengths of Ni/Cu(A)-Ti(A) and Ni/Cu(A)-Ti(B) as a function of Cu content in TiNiCu alloys are presented. It can be observed that, with increasing Cu content in TiNiCu martensite, the bond length between Ni/Cu(A) and Ti(B) atoms increases, leading to an increase of lattice parameter b, which agrees well with previous observations [25]. For the bond length between Ni/Cu(A) and Ti(A) atoms, it decreases initially and then increases.…”

Section: Resultssupporting

confidence: 90%

“…The atomic radii of Ti, Ni and Cu are 1.45 Å, 1.29 Å and 1.28 Å, respectively. As the atomic radius of Cu is slightly smaller than that of Ni, the size mismatch is not significant, which is consistent with the previous observation that there is no dramatic change of crystal structure when substituting Cu in TiNiCu martensitic alloys [25]. Our earlier work noted that more electrons escape from the Ti atoms in comparison with the equiatomic TiNi binary alloy with increasing Cu content [25].…”

Section: Resultssupporting

confidence: 90%

“…Using a SeqQuest code based on the DFT, a new martensite structure in TiNi denoted as the B19″ phase was reported by Vishnu et al [22]. Moreover, using experimental and theoretical DFT methods, the bonding and microstructural stability in Ni55Ti45 has been studied by Stott et al [23,24] The present authors' earlier computational study [25] found that with Cu addition to TiNi, the martensite lattice parameters a and c and the monoclinic angle decrease, whereas the lattice parameter b increases with increasing Cu content. Meanwhile, more electrons escaped from the Ti atoms as the Cu atoms attract more electrons compared to Ni atoms.…”

Section: Introductionmentioning

confidence: 78%

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Effect of Cu Content on Atomic Positions of Ti50Ni50−xCux Shape Memory Alloys Based on Density Functional Theory Calculations

Gou

Liu

2015

Metals

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Abstract:The study of crystal structures in shape memory alloys is of fundamental importance for understanding the shape memory effect. In order to investigate the mechanism of how Cu content affects martensite crystal structures of TiNiCu alloys, the present research examines the atomic displacement of Ti50Ni50−xCux (x = 0, 5, 12.5, 15, 18.75, 20, 25) shape memory alloys using density functional theory (DFT). By the introduction of Cu atoms into TiNi martensite crystal to replace Ni, the displacements of Ti and Ni/Cu atoms along the x-axis are obvious, but they are minimal along the y-and z-axes. It is found that along the x-axis, the two Ti atoms in the unit cell move in opposite directions, and the same occurred with the two Ni/Cu atoms. With increasing Cu content, the distance between the two Ni/Cu atoms increases while the Ti atoms draw closer along the x-axis, leading to a rotation of the (100) plane, which is responsible for the decrease in the monoclinic angle. It is also found that the displacements of both Ti atoms and Ni/Cu atoms along the x-axis are progressive, which results in a gradual change of monoclinic angle and a transition to B19 martensite crystal structure.

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Section: Resultssupporting

confidence: 91%

Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 78%

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Effect of Cu Content on Atomic Positions of Ti50Ni50−xCux Shape Memory Alloys Based on Density Functional Theory Calculations

Gou

Liu

2015

Metals

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“…Moreover, this change is gradual. From Table 4.6, Table 4.7, Table 4.8, Table 4.9 and As the atomic radii of Cu is slightly smaller than that of Ni, the size mismatch is not significant, which is consistent with previous observation that there is no dramatic change of crystal structure when substituting Cu in TiNiCu martensitic alloys [185].…”

Section: Resultssupporting

confidence: 89%

A first-principle study on lattice properties and atom positions of TiNiCu shape memory alloys

Gou¹

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Yong. Without their academic guidance and invaluable encouragement, the studies presented in this report would neither have started nor finished. They are not only professional mentors but also wonderful gentlemen. From them, I have not only learnt the methods and knowledge associated with the research, but also a lifelong treasure of the smart thinking and analytical skill. Then, many thanks go to my senior apprentice, Yan Lina. During the research period, she gave me many constructive suggestions and supports both on my research and course work. Meanwhile, I would like to thank all my teachers, friends and families, for their consistent support and encouragement. Many thanks also go to High Performance Computing Center at Nanyang Technological University. Parts of the computations were carried out on their hpc-rds platform. Last but not least, my hearted thanks go to my parents and my girlfriend Gu Yan. Their consistent love, encouragement and support are always the best impetus to my studies as well as to my life.

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Effect of Cu on Amorphization of a TiNi Alloy during HPT and Shape Memory Effect after Post‐Deformation Annealing

et al. 2019

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A ternary TiNiCu shape memory alloy is subjected to high‐pressure torsion (HPT) followed by post‐deformation annealing (PDA) to study the effect of Cu (5 at%) on amorphization after HPT processing and to investigate the microstructural evolution and shape memory effect (SME) after PDA. The results show that even after 20 revolutions the ternary alloy contains nanocrystalline areas and the microstructure is not fully amorphous. An easier martensite‐to‐austenite transformation and minor remaining austenite in the ternary alloy are responsible for suppressing amorphization. Post‐deformation annealing at 673 K provides nanocrystalline microstructures containing an R‐phase with a minor martensitic B19' phase in the ternary alloy. The SME of this alloy after PDA is not as satisfactory as that of the binary alloy processed through similar conditions because of the existence of a high volume fraction of the R‐phase. However, the total recovered strain of the ternary alloy after PDA for 30 min has a maximum value of 6.5%.

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An investigation on the crystal structures of Ti50Ni50−xCux shape memory alloys based on density functional theory calculations

Cited by 33 publications

References 39 publications

Effect of Cu Content on Atomic Positions of Ti50Ni50−xCux Shape Memory Alloys Based on Density Functional Theory Calculations

Effect of Cu Content on Atomic Positions of Ti50Ni50−xCux Shape Memory Alloys Based on Density Functional Theory Calculations

A first-principle study on lattice properties and atom positions of TiNiCu shape memory alloys

Effect of Cu on Amorphization of a TiNi Alloy during HPT and Shape Memory Effect after Post‐Deformation Annealing

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