This research is related to the investigation of the influence of copper additions on phase transformation, microstructure and mechanical characterization of equiatomic NiTi shape-memory alloys. A typical vacuum arc melting furnace was used in the preparation of Ni50-xTi50Cux (x = 2, 5, 10, and 15 at.%) shape-memory alloys. The crystalline phase formation and phase transformation temperature were studied using X-ray diffraction and a differential scanning calorimeter. The morphology and chemical composition of the annealed samples were investigated using a field emission scanning electron microscope and energy-dispersive X-ray spectrometer analysis. The Vickers microhardness test was utilized in the analysis of the homogeneity of the alloy. The experimental results obtained from X-ray diffraction confirmed the coexistence of austenite and martensite phases along with the presence of a Ti2Ni and minor rutile phases. The crystalline sizes of the alloys were in the range of 42 to 78nm. An energy-dispersive spectrometer validated the distinct phases and precipitates in the alloys. The size and dispersion of the secondary phase in the alloy showed a significant influence on the increased hardness from 407HV to 470HV. The following NiTiCu alloy compositions were employed for low-temperature applications since their transition temperatures were below 100°C.
JaniJMLearyMSubicA, et al.A review of shape memory alloy research, applications and opportunities. Mater Des2014; 56: 1078–1113.
2.
OliveiraJPShenJEscobarJD, et al.Laser welding of H-phase strengthened Ni-rich NiTi-20Zr high temperature shape memory alloy. Mater Des2021; 202: 109533.
3.
ZuoXZhangWChenY, et al.Wire-based directed energy deposition of NiTiTa shape memory alloys: microstructure, phase transformation, electrochemistry, X-ray visibility and mechanical properties. Addit Manuf2022; 59: 103115.
4.
ShenJZengZNematollahiM, et al.In-situ synchrotron X-ray diffraction analysis of the elastic behaviour of martensite and H-phase in a NiTiHf high temperature shape memory alloy fabricated by laser powder bed fusion. Addit Manuf Lett2021; 1: 100003.
5.
ZengZOliveiraJPYangM, et al.Functional fatigue behavior of NiTi-Cu dissimilar laser welds. Mater Des2017; 114: 282–287.
6.
NamTHSaburiTNakataY, et al.Shape memory characteristics and lattice deformation in Ti–Ni–Cu alloys. Mater Trans JIM1990; 31: 1050–1056.
7.
SharmaNJangraKKRajT. Fabrication of NiTi alloy: a review. Proc IMechE, Part L: J Mater: Des Appl2018; 232: 250–269.
8.
GuimaraesRPPixnerFTrimmelG, et al.The electron beam freeform fabrication of NiTi shape memory alloys. Part I: microstructure and physical-chemical behavior. Proc IMechE, Part L: J Mater: Des Appl2021; 235: 709–716.
9.
NespoliAVillaEBesseghiniS. Characterization of the martensitic transformation in Ni50-xTi50Cux alloys through pure thermal measurements. J Alloys Compd2011; 509: 644–647.
10.
ParviziSHashemiSMAsgariniaFNematollahiMElahiniaM. Effective parameters on the final properties of NiTi-based alloys manufactured by powder metallurgy methods: a review. Prog Mater Sci2021; 117: 100739.
11.
De AraújoCJDa SilvaNJDa SilvaMM, et al.A comparative study of Ni-Ti and Ni-Ti-Cu shape memory alloy processed by plasma melting and injection molding. Mater Des2011; 32: 4925–4930.
12.
GoryczkaTVan HumbeeckJ. Niticu shape memory alloy produced by powder technology. J Alloys Compd2008; 456: 194–200.
13.
GouLLiuYNgTY. An investigation on the crystal structures of Ti50Ni50–xCux shape memory alloys based on density functional theory calculations. Intermetallics2014; 53: 20–25.
14.
TatarCAcarRQaderIN. Investigation of thermodynamic and microstructural characteristics of NiTiCu shape memory alloys produced by arc-melting method. Eur Phys J Plus2020; 135: 1–1.
15.
SampathVSrinithiRSantoshS, et al.The effect of quenching methods on transformation characteristics and microstructure of an niticu shape memory alloy. Trans Indian Inst Met2020; 73: 1481–1488.
16.
LiBWangLWangB, et al.Electron beam freeform fabrication of NiTi shape memory alloys: crystallography, martensitic transformation, and functional response. Mater Sci Eng A2022; 843: 143135.
17.
ZhuJWuHHWuY, et al.Influence of Ni4Ti3 precipitation on martensitic transformations in NiTi shape memory alloy: r phase transformation. Acta Mater2021; 207: 116665.
18.
JiangSYZhangYQZhaoYN, et al.Influence of Ni4Ti3 precipitates on phase transformation of NiTi shape memory alloy. Trans Nonferrous Met Soc China2015; 25: 4063–4071.
19.
PanGBalagnaCMartinoL, et al.Microstructure and transformation temperatures in rapid solidified Ni-Ti alloys. Part I: the effect of cooling rate. J Alloys Compd2014; 589: 628–632.
20.
TadayyonGMazinaniMGuoY, et al.The effect of annealing on the mechanical properties and microstructural evolution of Ti-rich NiTi shape memory alloy. Mater Sci Eng A2016; 662: 564–577.
21.
KökMAteşG. The effect of addition of various elements on properties of NiTi-based shape memory alloys for biomedical application. Eur Phys J Plus2017; 132: 1–6.
22.
FrenzelJWieczorekAOpahleI, et al.On the effect of alloy composition on martensite start temperatures and latent heats in Ni–Ti-based shape memory alloys. Acta Mater2015; 90: 213–231.
23.
YoungMLDeFouwJDFrenzelJ, et al.Cast-replicated NiTiCu foams with superelastic properties. Metall Mater Trans A2012; 43: 2939–2944.
24.
BhattacharyaK. Microstructure of martensite: why it forms and how it gives rise to the shape-memory effect. United Kingdom: OUP Oxford, 2003.
25.
MorakabatiMKheirandishSAboutalebiM, et al.The effect of Cu addition on the hot deformation behavior of NiTi shape memory alloys. J Alloys Compd2010; 499: 57–62.
26.
YangCChengQRLiuLH, et al.Effect of minor Cu content on microstructure and mechanical property of NiTiCu bulk alloys fabricated by crystallization of metallic glass powder. Intermetallics2015; 56: 37–43.
27.
GhadimiMShokuhfarAZolriasateinA, et al.Morphological and structural evaluation of nanocrystalline NiTiCu shape memory alloy prepared via mechanical alloying and annealing. Mater Lett2013; 90: 30–33.
28.
HansenAWBeltramiLVAntoniniLM, et al.Oxide formation on NiTi surface: influence of the heat treatment time to achieve the shape memory. Mater Res2015; 18: 1053–1061.
29.
FrenzelJGeorgeEPDlouhyA, et al.Influence of Ni on martensitic phase transformations in NiTi shape memory alloys. Acta Mater2010; 58: 3444–3458.
30.
GilFJManeroJMPlanellJA. Effect of grain size on the martensitic transformation in NiTi alloy. J Mater Sci1995; 30: 2526–2530.
31.
ShivaSPalaniIAMishraSK, et al.Influence of Cu addition to improve shape memory properties in NiTi alloys developed by laser rapid manufacturing. J Laser Micro Nanoen2016; 11: 153.
32.
ShivaSYadaiahNPalaniIA, et al.Thermo mechanical analyses and characterizations of TiNiCu shape memory alloy structures developed by laser additive manufacturing. J Manuf Process2019; 48: 98–109.
33.
CallistiMTichelaarFDMellorBG, et al.Effects of Cu on the microstructural and mechanical properties of sputter deposited Ni-Ti thin films. Surf Coat Technol2013; 237: 261–268.
