NiTiCu thin walls were produced by twin-wire arc additive manufacturing(T-WAAM)using commercial NiTi and Cu wires as the feedstock materials.This approach aims to solve the problems typically associated with large pha...NiTiCu thin walls were produced by twin-wire arc additive manufacturing(T-WAAM)using commercial NiTi and Cu wires as the feedstock materials.This approach aims to solve the problems typically associated with large phase transformation hysteresis in NiTi shape memory alloys.The microstructure,mechanical properties,and phase transformation behavior of the as-deposited NiTiCu alloy were comprehensively examined.The results re-vealed that the as-deposited NiTiCu alloy was well-formed,with its microstructure showed columnar,equiaxed,and needle-like grains,depending on the location within the deposited walls.The microhardness gradually in-creased from the first to the third layer.The Cu content was 20.80 at%,and Cu-based precipitates were formed in the as-deposited NiTiCu.The volume fractions and lattice parameters of the matrix and precipitates in the as-deposited NiTiCu material were analyzed using high-energy synchrotron X-ray diffraction.The martensitic phase was identified as a B19 crystal structure,and the as-deposited NiTiCu underwent a one-step B2-B19 phase transformation.The tensile strength and fracture strain were approximately 232 MPa and 3.72%,respectively.In particular,the addition of Cu narrowed the phase transformation hysteresis of the as-deposited NiTiCu alloy from 24.4 to 7.1◦C compared with conventional binary NiTi alloys.This study expands the potential of T-WAAM in modifying the phase transformation behavior of NiTi-based ternary alloys.展开更多
For NiTiCu SMA, the Ni atoms are substituted by Cu atoms, which not only greatly reduce the alloy cost, but also have excellent shape memory effect. Four kinds of shape memory alloy films (Ni49.6Ti50.4, Ni48.2Ti50.4Cu...For NiTiCu SMA, the Ni atoms are substituted by Cu atoms, which not only greatly reduce the alloy cost, but also have excellent shape memory effect. Four kinds of shape memory alloy films (Ni49.6Ti50.4, Ni48.2Ti50.4Cu1.4, Ni45.6Ti50.4Cu4, Ni42.7Ti50.4Cu6.9) were prepared using magnetron sputtering. Corrosion behaviors of the four films in phosphate buffered saline (PBS) solutions at 37°C were examined using electrochemical impedance spectroscopy (EIS) method. It was found that the corrosion resistance of the NiTi film is superior to the three NiTiCu films. The EIS data were fitted using a parallel resistance-capacitance (as a constant phase element) circuit associated with the surface oxide film. The thickness of the surface oxide layer of the three NiTiCu films increases with applied potential till 0.8 V, while that of the NiTi film can reach to 1.2 V.展开更多
本文用差示扫描量热法研究了 Cu 对 NiTi 记忆合金马氏体相变点及相变潜热的影响。结果表明,以 Cu 代替 Ni 至30 at.%,合金仍具有良好的记忆性能;合金相变温度及相变潜热值略有变化,相变滞后明显减小;Cu 含量对合金相变类型没有影响。...本文用差示扫描量热法研究了 Cu 对 NiTi 记忆合金马氏体相变点及相变潜热的影响。结果表明,以 Cu 代替 Ni 至30 at.%,合金仍具有良好的记忆性能;合金相变温度及相变潜热值略有变化,相变滞后明显减小;Cu 含量对合金相变类型没有影响。相变潜热值△H 与 T_0=1/2(A_s+M_s)并不存在严格的直线关系。Cu 含量超过7.5at.—%时,合金的热加工性能变差。展开更多
In the present work, the hot workability and microstructural evolution of NiTi47.TCu6.3 （at.%） shape memory alloy were investigated by using wedge-rolling test. The wedge specimens were subjected to hot rolling at t...In the present work, the hot workability and microstructural evolution of NiTi47.TCu6.3 （at.%） shape memory alloy were investigated by using wedge-rolling test. The wedge specimens were subjected to hot rolling at the temperatures of 700-1000℃. The microstructural evolutions at the strains of 0.05, 0.15, 0.2, 0.25 and 0.3 were then characterized by optical microscopy and scanning electron microscopy （SEM） as well as energy dispersive spectrometry （EDS） technique. Depending on the deformation temperature and strain, the dynamic recrystallization （DRX） could occur, leading to the refining of the microstructure. At low temperatures of 700 and 800℃ there was no sign of DRX at all studied strains. At these temperatures, the formed fine needle-like precipitates pinned the grain boundaries and prevented them from bulging/migration. By contrast, at higher temperatures of 900 and 1000℃, the DRX took place at the critical strains lower than 0.25 and 0.15, respectively. However, at higher temperatures, strain-induced-boundary-migration （SIBM） mechanism resulted in the formation of DRX grains.展开更多
基金supported by National Natural Science Founda-tion of China(Grant No.52175292)Science and Technology Project of Sichuan Province(Grant Nos.23NSFJQ0064,2022YFQ0058)+2 种基金Guangdong Basic and Applied Basic Research Foundation(Grant No.2021B1515140048)JPO and JS acknowledge the funding by na-tional funds from Fundação para a Ciência e a Tecnologia(FCT),I.P.,within the scope of projects LA/P/0037/2020,UIDP/50025/2020,and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostruc-tures,Nanomodelling,and Nanofabrication-i3NDESY(Hamburg,Germany),a member of the Helmholtz Associa-tion HGF,for providing the experimental facilities.Part of this study was conducted at PETRA III.The research leading to this result was sup-ported by project CALIPSOplus under Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020.
文摘NiTiCu thin walls were produced by twin-wire arc additive manufacturing(T-WAAM)using commercial NiTi and Cu wires as the feedstock materials.This approach aims to solve the problems typically associated with large phase transformation hysteresis in NiTi shape memory alloys.The microstructure,mechanical properties,and phase transformation behavior of the as-deposited NiTiCu alloy were comprehensively examined.The results re-vealed that the as-deposited NiTiCu alloy was well-formed,with its microstructure showed columnar,equiaxed,and needle-like grains,depending on the location within the deposited walls.The microhardness gradually in-creased from the first to the third layer.The Cu content was 20.80 at%,and Cu-based precipitates were formed in the as-deposited NiTiCu.The volume fractions and lattice parameters of the matrix and precipitates in the as-deposited NiTiCu material were analyzed using high-energy synchrotron X-ray diffraction.The martensitic phase was identified as a B19 crystal structure,and the as-deposited NiTiCu underwent a one-step B2-B19 phase transformation.The tensile strength and fracture strain were approximately 232 MPa and 3.72%,respectively.In particular,the addition of Cu narrowed the phase transformation hysteresis of the as-deposited NiTiCu alloy from 24.4 to 7.1◦C compared with conventional binary NiTi alloys.This study expands the potential of T-WAAM in modifying the phase transformation behavior of NiTi-based ternary alloys.
文摘For NiTiCu SMA, the Ni atoms are substituted by Cu atoms, which not only greatly reduce the alloy cost, but also have excellent shape memory effect. Four kinds of shape memory alloy films (Ni49.6Ti50.4, Ni48.2Ti50.4Cu1.4, Ni45.6Ti50.4Cu4, Ni42.7Ti50.4Cu6.9) were prepared using magnetron sputtering. Corrosion behaviors of the four films in phosphate buffered saline (PBS) solutions at 37°C were examined using electrochemical impedance spectroscopy (EIS) method. It was found that the corrosion resistance of the NiTi film is superior to the three NiTiCu films. The EIS data were fitted using a parallel resistance-capacitance (as a constant phase element) circuit associated with the surface oxide film. The thickness of the surface oxide layer of the three NiTiCu films increases with applied potential till 0.8 V, while that of the NiTi film can reach to 1.2 V.
文摘本文用差示扫描量热法研究了 Cu 对 NiTi 记忆合金马氏体相变点及相变潜热的影响。结果表明,以 Cu 代替 Ni 至30 at.%,合金仍具有良好的记忆性能;合金相变温度及相变潜热值略有变化,相变滞后明显减小;Cu 含量对合金相变类型没有影响。相变潜热值△H 与 T_0=1/2(A_s+M_s)并不存在严格的直线关系。Cu 含量超过7.5at.—%时,合金的热加工性能变差。
文摘In the present work, the hot workability and microstructural evolution of NiTi47.TCu6.3 （at.%） shape memory alloy were investigated by using wedge-rolling test. The wedge specimens were subjected to hot rolling at the temperatures of 700-1000℃. The microstructural evolutions at the strains of 0.05, 0.15, 0.2, 0.25 and 0.3 were then characterized by optical microscopy and scanning electron microscopy （SEM） as well as energy dispersive spectrometry （EDS） technique. Depending on the deformation temperature and strain, the dynamic recrystallization （DRX） could occur, leading to the refining of the microstructure. At low temperatures of 700 and 800℃ there was no sign of DRX at all studied strains. At these temperatures, the formed fine needle-like precipitates pinned the grain boundaries and prevented them from bulging/migration. By contrast, at higher temperatures of 900 and 1000℃, the DRX took place at the critical strains lower than 0.25 and 0.15, respectively. However, at higher temperatures, strain-induced-boundary-migration （SIBM） mechanism resulted in the formation of DRX grains.
