Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 7-Day Trial for You or Your Team.

Learn More →

The effects of Ru, Cu, Zr and Hf on mechanical properties in Ti-Pt high temperature shape memory alloys

The effects of Ru, Cu, Zr and Hf on mechanical properties in Ti-Pt high temperature shape memory... Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 The effects of Ru, Cu, Zr and Hf on mechanical properties in Ti-Pt high temperature shape memory alloys M P Mashamaite, H R Chauke and P E Ngoepe Materials Modelling Centre, School of Physical and Mineral Sciences, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa Email: [email protected] Abstract. Shape memory alloys (SMAs) have been widely used in the fields of actuators and aerospace industry due to their pseudo-elasticity and shape memory effect which are displayed in phase transformations. The martensitic transformations (MT) of TiPt is much higher, at approximately 1273 K and this is considered to be of potential technological interest for elevated temperature SMA applications. TiPt based alloys exhibit very low shape memory effect due to low critical stress for slip deformation compared to the stress required for martensitic transformation, hence it is necessary to enhance the mechanical properties of the equiatomic alloy. The first principles approach was employed to study the effect of the third element (M = Ru, Cu, Zr, and Hf) on the TiPt shape memory alloy. The supercell approach in VASP was used to substitute Pt with Ru and Cu, Ti with Zr and Hf on the TiPt structure to evaluate their mechanical stability from elastic properties for actuators and higher temperature applications. The Ti Pt Ru and Ti Pt Cu decreases in density with increase in Ru and Cu concentration, 50 50-x x 50 50-x x whilst the Ti Zr Pt and Ti Hf Pt substitution increases with an increase in their 50-x x 50 50-x x 50 concentration, which result in larger lattice parameters. The heats of formation suggest that Ti Pt Ru substitution is more thermodynamically stable than Ti Pt Cu substitution, and 50 50-x x 50 50-x x Ti Hf Pt substitution is more stable than Ti Zr Pt . The elastic properties suggest that the 50-x x 50 50-x x 50 ternary structures become mechanically stable with an increase of the third element. The Ti Pt 50 50- Ru and Ti Pt Cu substitution became more ductile with the increase in concentration. Zr x x 50 50-x x and Hf substitution became more ductile at higher compositions (31.75 – 43.75 at.%). The Ru and Hf substitutions have potential to be used for high-temperature applications. 1. Introduction Shape memory amalgams (SMAs) that display shape memory impact over 373 K can possibly be utilized for higher temperature application, for example, air ship turbine motors, high-temperature actuators, thermal security, and so forth. [1]; these are known as high-temperature shape memory alloys (HTSMAs). Of all the known SMA pieces, the NiTi compound framework has been examined most broadly and is utilized in the best number of business applications. This alloy exhibits strong shape memory effect (SME), and pseudoelastic behavior under the right conditions, which makes this material ideal for a variety of applications [2]. HTSMAs are produced by adding the ternary (third elements) such as Pd, Pt, Hf, Au, and Zr to NiTi for whose temperature can be shifted anywhere between 373 and 973 K [3]. Some of these materials were reported to effectively increase the transformation temperature of NiTi [4]. Hafnium and Zr addition to NiTi has also been investigated due to their lower cost [5]. (Ti Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1 Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 + Hf, Zr) - rich NiTi amalgams have weaknesses, for example, an enormous warm hysteresis, poor thermal steadiness, and fragility [6]. On the other hand, equiatomic TiPt exhibits martensitic phase transformation above 1200 K, ~400K higher than equiatomic TiAu and ~500K higher than equiatomic TiPd [7, 8]; these are categorized as HTSMAs due to their thermo-elastic B2 martensitic phase transformation to B19 above 700 K [1, 9, 10]. It was also found that TiPt alloys exhibited negligible SME (11%), due to the low critical stress for slip deformation compared to the stress required for martensitic reorientation [11]. Yoko Yamabe- Mitarai and co-workers [12] additionally detailed that Ti – 50Pt displayed a solitary yielding marvel and low quality (~450MPa) in martensite and exceptionally low quality (~20 MPa) in the B2 area. Equiatomic Equiatomic TiPt displayed thermo-flexible martensitic phase change, and may not be utilized for high-temperature shape memory materials applications, because of irrelevant SME and low reinforcing in the austenite region. Otherwise, if the shape memory properties can be improved, the B2 phase could be utilized for higher temperature applications [13, 14]. However, research on TiPt enhancement with Zr and Ru partial substitution were discovered powerful for improving the high- temperature quality and shape memory properties, bringing about an expansion in critical stress for slip disfigurement [14]. Cobalt addition was reported to stabilize the B2 phase at lower temperatures and reduced the martensitic transformation temperature due to higher values of tetragonal shear modulus (C′) [15]. Furthermore, it is important to strengthen both martensite and austenite phase against deformation, which is significant for the development of SMAs for high-temperature actuator applications [16]. In the previous work, the effect of a third element Ru, Co, Cu, Zr and Hf on the B19 Ti Pt M was 50 50-x x investigated for x=5 and Ru addition was more effective and preferred for high-temperature shape memory alloys [17]. It has been suggested that Ru and Cu are preferential for Pt substitution, while Zr and Hf showed promising shape memory trends when substituted for Ti site [18] In this study we investigated the thermodynamic and elastic properties of the B2 ternary Ti Pt M M=Ru and Cu and 50 50-x x Ti M Pt M=Zr and Hf shape memory alloys by employing the first principles method for 50-x x 50 understanding their martensitic transformation behavior and mechanical properties. 2. Methodology We employed the first principles density functional theory (DFT) in the Vienna ab initio Simulation Package (VASP) code [19, 20] with the projector augmented wave (PAW) [21]. An energy cut–off of 500 eV was used, to achieve a good convergence of the parameters. We used the generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional [22]. The Brillouin zone integrations were performed with a k-spacing of 0.25 according to Monkhorst and Pack [23]. A 2×2×2 supercell of TiPt was used to substitute a portion of the Pt with Ru and Cu, and Ti with Zr and Hf. 3. Results and Discussion 3.1. Structural and Thermodynamic Properties The calculated equilibrium lattice parameters of the B2 Ti Pt M where M=Ru and Cu are shown in 50 50-x x Figure 1 (a), B2 Ti50-xMxPt50 M=Zr and Hf in Figure 1 (b) (x=6.25, 18.75, 25, 31.75, and 43.75), where a = b = c. The lattice parameters decreased with increased Ru and Cu content with Ti Pt Ru having 50 6.25 43.75 the lowest value of lattice parameter at a=3.085 Å. Conversely, Ti Zr Pt and Ti Hf Pt 50-x x 50 50-x x 50 substitutions increased with an increase in Zr and Hf content, Ti Hf Pt being the lowest at a=3.304 43.75 6.25 50 Å. Figure 1 (c) and (d) show the densities of Ti Pt M where M=Ru and Cu and Ti M Pt M=Zr and 50 50-x x 50-x x 50 Hf against composition. The density of the Ti Pt Ru and Ti Pt Cu substitutions decreased with 50 50-x x 50 50-x x increase in Ru and Cu content, which was also verified by the lattice parameters, this might be due to their atomic radius of Ru and Cu being less than that of Pt. So partial substitution of Pt on Ti Pt M 50 50-x x with Ru was expected to decrease the density of the TiPt alloy [24]. Ti Pt Cu was found to have 50 6.25 43.75 2 Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 the lowest density. On the contrary, Ti Hf Pt increased as 43.75>x>6.25, Ti Zr Pt was observed 50-x x 50 50-x x 50 with a minimal increase with an increased Zr composition. It can also be seen that the atomic radii of Zr and Hf are much greater than both Ti and Pt, resulting in greater densities on the ternary alloys. 3.18 3.36 (b) (a) Ti Pt Ru 3.34 50 50-x x Ti Zr Pt 50-x x 50 Ti Pt Cu 50 50-x x 3.16 3.32 3.30 3.14 3.28 Ti Hf Pt 50-x x 50 3.26 3.12 3.24 3.22 3.10 3.20 3.08 3.18 0 10 20 30 40 0 10 20 30 40 Ti Pt M (M=Ru and Cu) Ti M Pt (M=Zr and Hf) 50 50-x x 50-x x 50 13 17 (c) (d) Ti Hf Pt 12 50-x x 50 Ti Pt Ru 50 50-x x Ti Pt Cu 50 50-x x Ti Zr Pt 50-x x 50 6 12 0 10 20 30 40 0 10 20 30 40 Ti Pt M (M=Ru and Cu) Ti M Pt (M=Zr and Hf) 50 50-x x 50-x x 50 Figure 1. Equilibrium lattice parameters of (a) Ti Pt M (M=Ru and Cu) (b) Ti M Pt (M=Zr 50 50-x x 50-x x 50 and Hf) and densities of (c) Ti Pt M (M=Ru and Cu) (d) Ti M Pt (M=Zr and Hf) ternaries, 50 50-x x 50-x x 50 43.75>x>6.25. The heats of formation (ΔH ), of the intermetallic phase were calculated according to the relation [25]: 𝑡𝑃𝑇𝑖 ∆𝐻 = 𝐸 −[(1−𝑥 )𝐸 +𝑥 𝐸 ], 𝑓 𝑑𝑙𝑖𝑜𝑠 𝑑𝑙𝑖𝑜𝑠 (1) 𝑡𝑃𝑇𝑖 where 𝐸 , 𝐸 and 𝐸 are the total energies of an intermetallic compound, and basic Ti and Pt 𝑑𝑙𝑖𝑜𝑠 𝑑𝑙𝑖𝑜𝑠 in their particular ground-state crystal structures, while x and 1-x allude to the fragmentary convergences of the constituent components. The predicted heats of formation for Ti50Pt50-xMx where M=Ru and Cu and Ti50-xMxPt50 M=Zr and Hf are shown in Figure 2. The heats of formation suggest that the small composition of Ti Pt Ru (– 50 43.75 6.25 0.748 eV/atom) and Ti Pt Cu (–0.693 eV/atom) are more stable; as the Cu content is increased 50 43.75 6.25 the Ti Pt Cu became unstable. Ru is more stable than Cu substitution on Ti Pt M . On the 50 50-x x 50 50-x x contrary, Ti Zr Pt (–0.908 eV/atom) and Ti Hf Pt (–0.966 eV/atom) suggest that they are 6.25 43.75 50 6.25 43.75 50 more stable substitutions. Ti Zr Pt and Ti Hf Pt became more stable when their concentration 50-x x 50 50-x x 50 was increased and Hf substitution became more stable. Density (Mg/m ) Lattice parameters (Å) Density (Mg/m ) Lattice parameters (Å) 𝑃𝑡 𝑇𝑖 𝑃𝑡 𝑇𝑖 Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 -0.1 -0.76 -0.78 (a) (b) -0.2 Ti Pt Cu 50 50-x x -0.80 -0.82 -0.3 -0.84 Ti Zr Pt -0.4 50-x x 50 -0.86 -0.88 -0.5 -0.90 -0.6 -0.92 -0.94 Ti Pt Ru 50 50-x x Ti Hf Pt -0.7 50-x x 50 -0.96 -0.8 -0.98 0 10 20 30 40 0 10 20 30 40 Ti Pt M (M=Ru and Cu) Ti M Pt (M=Zr and Hf) 50 50-x x 50-x x 50 Figure 2. Heats of formation of (a) Ti Pt M (M=Ru and Cu) (b) Ti M Pt (M=Zr and Hf), where 50 50-x x 50-x x 50 43.75 >x>6.25 3.2. Elastic Properties The accurate calculation of elasticity is vital for picking up knowledge into the mechanical stability and elastic properties of compounds. The elastic constants of a cubic crystal have three (C , C , and C ) 11 22 44 independent elastic constants. Applying two sorts of strains (ε1 and ε4) on the cubic system give stresses identifying with three flexible coefficients, yielding a proficient technique for obtaining elastic constants. This technique has been effectively used to study the elastic properties of a scope of materials including metallic frameworks [26]. For a cubic crystal, the mechanical stability conditions are given by [27]. C >0, C >0, + C >|C | and C +2C >0, 11 44 11 12 11 12 (2) The elastic constants were evaluated to observe the impact of ternary substitution Pt with Ru and Cu, and Ti with Zr and Hf. All the independent elastic constants C , C , and C for Ti Pt M where 11 12 44 50 50-x x M=Ru and Cu and Ti M Pt M=Zr and Hf were positive which indicated mechanical stability of the 50-x x 50 structures. The C >C at 25 at.% and 43.75 at.% for Ti Pt Ru in Figure 3 (a), C >C at 18.75– 11 12 50 50-x x 11 12 43.75 at.% for Ti Pt Cu in Figure 3(b), C >C at Ti Zr Pt in Figure 3 (c), and C >C at 25– 50 50-x x 11 12 6.25 43.75 50 11 12 43.75 at.% for Ti50-xHfxPt50 in figure 3 (d), which contributed to positive C′. However, the C44 increase minimally with increase in Ti Pt Ru and Ti Pt Cu substitutions, suggesting a good correlation 50 50-x x 50 50-x x between C and C′ moduli, while decreasing minimally for Ti Zr Pt and Hf substitution. The 44 50-x x 50 positive shear suggests that all the ternary compositions above satisfied all conditions of mechanical stability of the cubic crystal. 400 220 200 (b) (a) C 300 11 200 120 100 C 60 C 0 10 20 30 40 0 10 20 30 40 Ti Pt Ru 50 50-x x Ti Pt Cu 50 50-x x C , C and C (GPa) 11 12 44 Heats of formation (H ) C , C and C (GPa) 11 12 44 Heats of formation (H ) f Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 220 250 (c) (d) 180 200 160 12 140 150 100 100 60 50 20 0 0 10 20 30 40 0 10 20 30 40 Ti Zr Pt Ti Hf Pt 50-x x 50 50-x x 50 Figure 3. Independent elastic properties C (C , C , and C ) (GPa) of (a) Ti Pt Ru (b) Ti Pt ij 11 12 44 50 50-x x 50 50- Cu (c) Ti Zr Pt (d) Ti Hf Pt , where 43.75>x>6.25 x x 50-x x 50 50-x x 50 The Ru and Cu substitution became mechanically stable with an increase in content, 25 – 43.75 at.% Ru and Cu from 18.75 at.% as shown in Figure 4 (a), Zirconium substitution stabilizes around 43.75 at.%, whilst Hf from 25 at.% in Figure 4 (b). The C′ increases with increase in Ru, Cu, Zr, and Hf content, it is also observed that smaller C′ values lead to larger anisotropy (A). These suggest that the Group 4 substitution stabilizes with an increase in Zr and Hf content, Ru belongs to Group 8, a similar trend was observed with the heats of formation; this might be due to Ru having a lower atomic radius than both Ti and Pt. Ti50Pt50-xCux in Figure 4 (a) stabilized around 18.75 at.% and it also noted that Cu has an atomic radius less than that of Pt, hence the observed curve. Furthermore, Ru substitution reduced the martensitic transformation temperature of TiPt [14] more than Ti Pt Cu , indicated by higher C′, which is consistent with the experimental findings at lower 50 6.25 43.75 concentrations for Ru substitution. The C′ moduli of Ti Pt Ru correspond with A of 0.78, closer 50 6.25 43.75 to unity (A≈1) [28]. The Hf substitution in Figure 4 (b) increased the martensitic transformation temperature of the Ti Pt since it gave the lowest C′ at 6.25 at.%, with an A value of 0.87. The Bulk 50-x 50 modulus (B) measures the level of firmness, or the energy required to deliver a given volume disfigurement [29]. In Figure 4 (c), Bulk moduli for Ti Pt Ru increased with an increase in Ru 50 50-x x content, suggesting that the structure became more hardened, while Ti Pt Cu decreased with 50 50-x x increased Cu content, suggesting that it became less hardened. Ti Zr Pt and Ti Hf Pt in Figure 4 50-x x 50 50-x x 50 (d) both decreased with increase in Zr and Hf content. These suggest that to maintain the hardness of Ti Pt Ru can be used with higher substitutional content, while Ti Pt Cu , Ti Zr Pt , and Ti 50 50-x x 50 50-x x 50-x x 50 50- Hf Pt may have to be used at smaller substitutional content. x x 50 120 40 100 (a) (b) Ti Zr Pt 50-x x 50 -20 Ti Pt Cu 50 50-x x -40 -20 Ti Hf Pt 50-x x 50 -40 -60 Ti Pt Ru 50 50-x x -60 -80 -80 0 10 20 30 40 0 10 20 30 40 Ti M Pt (M=Zr and Hf) 50-x x 50 Ti Pt M (M=Ru and Cu) 50 50-x x C , C and C (GPa) 11 12 44 C' (GPa) C , C and C (GPa) 11 12 44 C' (GPa) Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 220 190 (c) (d) Ti Pt Ru 50 50-x x 200 Ti Hf Pt 186 50-x x 50 Ti Zr Pt 140 Ti Pt Cu 50-x x 50 50 50-x x 0 10 20 30 40 0 10 20 30 40 Ti M Pt (M=Zr and Hf) Ti Pt M (M=Ru and Cu) 50-x x 50 50 50-x x Figure 4. Shear moduli C′ (GPa) for (a) Ti Pt M (M=Ru, Cu) (b) Ti M Pt (M=Zr and Hf) and 50 50-x x 50-x x 50 their Bulk moduli (B) (a) Ti Pt M (M=Ru and Cu) (b) Ti M Pt (M=Zr and Hf). 50 50-x x 50-x x 50 According to Pugh, for metals to be considered ductile the Bulk to shear B/G ratio must be >1.75, otherwise, the metal is brittle [30]. In Figure 5 (a), the structures displayed ductility with an increase in Ru and Cu content, since the B/G >1.75. A similar trend was observed in Ti substitution with Zr and Hf in Figure 5 (b), and the dip on Zr 25 at.% was caused by lower values of G. Lower atomic percentages (6.25 at.%) for (Pt with Ru and Cu, Ti with Zr and Hf) were attributed to negative B/G ratio, which did not satisfy ductility conditions. Therefore, Ru at 6.25–18.75 at.%, Cu at 6.25 at.%, Zr at 6.25–25 at.%, and Hf at 18.75 at.% were brittle. 40 30 (b) (a) Ti Hf Pt 50-x x 50 30 20 Ti Pt Ru 50 50-x x 20 Ti Zr Pt 50-x x 50 Ti Pt Cu 50 50-x x -10 -10 -20 0 10 20 30 40 0 10 20 30 40 Ti Pt M (M=Ru and Cu) Ti M Pt (M=Zr and Hf) 50 50-x x 50-x x 50 Figure 5. B/G ratio for (a) Ti Pt M (M=Ru and Cu) (b) Ti M Pt (M=Zr and Hf), where 50 50-x x 50-x x 50 43.75>x>6.25. 4. Conclusions A computational modelling study on the thermodynamic and mechanical properties in Ti Pt M 50 50-x x (M=Ru and Cu) and Ti M Pt (M=Zr and Hf) where 0<x<50 was performed. The effect of the lattice 50-x x 50 parameter depends on the type of the alloying element and sub-lattice. The Ru and Cu showed a decrease in lattice parameter, while Zr and Hf show an increase. The thermodynamic stability for the ternary framework was explored by somewhat substituting a portion of the Pt with Ru and Cu, and Ti with Zr and Hf, we observed that Ru (–0.748 eV/atom) at 6.25 at.% and Hf (–0.966 eV/atom) at 43.75 at.% substitutions were the most stable structures. The elastic constant of both for Pt substitution and Ti substitution were found to be stable with all the moduli obeying the elastic stability criterion. The addition of Ru and Cu content in Pt and Zr and Hf in Ti increased C′ moduli of the cubic phase leading to a positive anisotropy. Ti Pt Ru and Ti Hf Pt increases the transformation temperature. This 50 50-x x 50-x x 50 demonstrated Ru having a place with Group 8 of the Periodic Table go about as B2 phase stabilizer than Cu in Pt substitution, followed by Hf in Ti substitution. Bulk Modulus B (GPa) B/G ratio Bulk Modulus B (GPa) B/G ratio Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 Acknowledgements The simulations were completed utilizing computer resources at the Materials Modelling Centre (MMC) at the University of Limpopo and the Centre for High Performance Computing (CHPC) in Cape Town. The authors recognize the South African Research Chair Initiative of the Department of Science and Technology and the National Research Foundation is profoundly perceived. References [1] Ma J, Karaman I and Noebe R D 2010 High temperature shape memory alloy Int. Mater. Rev. 55 [2] Kumar P K and Lagoudas D C 2008 Introduction to shape memory alloys Modeling and Eng. Application Lett. 11 [3] Funakubo H (Ed.), 1987 Shape Memory Alloys, Gordon and Breach Science Publishers [4] Suzuki Y, Xu Y, Morito S, Otsuka K and Mitose K 1998 Effects of boron addition on microstructure and mechanical properties of Ti–Td–Ni high-temperature shape memory alloys Mater. Lett. 36 85 [5] Carl M, Smith J D, Van Doren B and Young M L 2017 Effect of Ni-content on the transformation temperatures in NiTi-20 at. % Zr high temperature shape memory alloys Metals 7 511 [6] Hsieh S F, Wu S K 1998 Memory alloys a study on ternary Ti–rich TiNiZr shape memory alloys Mater. Charact. 41 151 [7] Donkersloot H C and van Vucht J H N 1970 Martensitic transformations in gold-titanium, palladium-titanium and platinum-titanium alloys near the equiatomic composition J. Less- Common Metals. 20 83 [8] Kawamura T, Tachi R, Inamura T, Hosoda H, Wakashima K, Hamada K and Miyazaki S 2006 Effects of ternary additions on martensitic transformation of TiAu Mater. Sci. Eng. A438 383 [9] Otsuka K, Oda K, Ueno Y, Piao M, Ueki T and Horikawa H 1993 The shape memory effect in a Ti Pd alloy Scripta Metall. Mater. 29 1355 50 50 [10] Yamabe-Mitarai Y, Arockiakumar R, Wadood A, Suresh K S, Kitashima T, Hara T, Shimojo M, Tasaki W, Takahashi M, Takahashi S and Hosoda H 2015 Ti(Pt, Pd, Au) based high temperature shape memory alloys in Materials Today: Proceedings 2 S517–S522 [11] Yamabe-Mitarai Y, Hara T, Miura S and Hosoda H 2010 Shape memory effect and pseudoelasticity of TiPt Intermetallics 18 2275 [12] Yamabe-Mitarai Y, Hara T, Miura S and Hosoda H 2006 Mechanical properties of Ti–50(Pt,Ir) high-temperature shape memory alloys Materi. Trans. 47 650 [13] Mahlangu R, Phasha M J, Chauke H R, Ngoepe P E 2013 Structural, elastic and electronic properties of equiatomic PtTi as potential high-temperature shape memory alloy Intermetallics 33 27 [14] Wadood A, Takahashi M, Takahashi S, Hosoda H and Yamabe-Mitarai Y 2013 High-temperature mechanical and shape memory properties of TiPt–Zr and TiPt–Ru alloys Mater. Sci. Eng. A564 34 [15] Mahlangu R 2015 Computational modelling studies of Ti Pt M (M: Co, Ni, Pd, Ir) shape 50 50-x x memory alloys. University of Limpopo: Thesis [16] Noebe R, Gaydosh D, Padula S, Garg A, Biles T, Nathal M. 2005 Properties and potential of two (Ni, Pt)Ti alloys for use as high-temperature actuator metals Proc. SPIE Int. Symp. Smart Struct. Mater. 5761 364 [17] Mashamaite M P, Chauke H R and Ngoepe P E 2018 Mechanical properties and stability of TiPt- M (M=Ru, Co, Cu, Zr and Hf) for high temperature applications IOP Conf. Ser.: Mater. Sci. Eng. 430 012019 [18] Bozzolo G, Mosca H O and Noebe R D 2007 Phase structure and site preference behavior of ternary alloying additions to PdTi and PtTi shape-memory alloys Intermetallics 15 901 [19] Hohenberg P and Kohn W 1964 Inhomogeneous electron gas Phys. Rev. B. 136 864 [20] Kohn W and Sham L J 1965 Self-consistent equations including exchange and correlation effects 7 Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 Phys. Rev 140 A1133 [21] Blöchl P E 1994 Projector augmented-plane wave method Phys. Rev. B. 50 17953 [22] Perdew J P, Burke K and Ernzerhof M 1996 Generalized gradient approximation made simple Phys. Rev. Lett. 77 3865 [23] Monkhorst H J and Pack J D 1976 Special points for Brillouin-zone integrations Phys. Rev. B. 13 [24] Wadood A and Yamabe-Mitarai Y 2014 TiPt–Co and TiPt–Ru high temperature shape memory alloys Mater. Sci. Eng. A601 106 [25] Fernando G W, Watson R E and Weinert M 1992 Heats of formation of transition-metal alloys: Full-potential approach and the Pt-Ti system Phys. Rev. B. 45 15 8233 [26] Zhang J M and Guo G Y 1997 Microscopic theory of the shape memory effect in TiNi Phys. Rev. Letters 78 4789 [27] Mehl M J and Klein B M 1994 First principles calculations of elastic properties of metals Inter. Comp. 1 1 [28] Goumri-Said S and Kanoun M B 2007 Theoretical investigations of structural, elastic, electronic and thermal properties of damiaoite PtIn Comp. Mat. Sci. 43 243 [29] Kittle C 1976 Introduction to solid state physics, 5th ed., New York: John Wiley & Sons [30] Pugh S F 1954 Relations between elastic moduli and plastic properties of polycrystalline pure metals Philos. Mag 45 843 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png IOP Conference Series Materials Science and Engineering IOP Publishing

The effects of Ru, Cu, Zr and Hf on mechanical properties in Ti-Pt high temperature shape memory alloys

Download PDF
8 pages

Loading next page...
 
/lp/iop-publishing/the-effects-of-ru-cu-zr-and-hf-on-mechanical-properties-in-ti-pt-high-CBnFEeBcNT

References (31)

Copyright
Copyright Published under licence by IOP Publishing Ltd
ISSN
1757-8981
eISSN
1757-899X
DOI
10.1088/1757-899X/655/1/012011
Publisher site
See Article on Publisher Site

Abstract

Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 The effects of Ru, Cu, Zr and Hf on mechanical properties in Ti-Pt high temperature shape memory alloys M P Mashamaite, H R Chauke and P E Ngoepe Materials Modelling Centre, School of Physical and Mineral Sciences, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa Email: [email protected] Abstract. Shape memory alloys (SMAs) have been widely used in the fields of actuators and aerospace industry due to their pseudo-elasticity and shape memory effect which are displayed in phase transformations. The martensitic transformations (MT) of TiPt is much higher, at approximately 1273 K and this is considered to be of potential technological interest for elevated temperature SMA applications. TiPt based alloys exhibit very low shape memory effect due to low critical stress for slip deformation compared to the stress required for martensitic transformation, hence it is necessary to enhance the mechanical properties of the equiatomic alloy. The first principles approach was employed to study the effect of the third element (M = Ru, Cu, Zr, and Hf) on the TiPt shape memory alloy. The supercell approach in VASP was used to substitute Pt with Ru and Cu, Ti with Zr and Hf on the TiPt structure to evaluate their mechanical stability from elastic properties for actuators and higher temperature applications. The Ti Pt Ru and Ti Pt Cu decreases in density with increase in Ru and Cu concentration, 50 50-x x 50 50-x x whilst the Ti Zr Pt and Ti Hf Pt substitution increases with an increase in their 50-x x 50 50-x x 50 concentration, which result in larger lattice parameters. The heats of formation suggest that Ti Pt Ru substitution is more thermodynamically stable than Ti Pt Cu substitution, and 50 50-x x 50 50-x x Ti Hf Pt substitution is more stable than Ti Zr Pt . The elastic properties suggest that the 50-x x 50 50-x x 50 ternary structures become mechanically stable with an increase of the third element. The Ti Pt 50 50- Ru and Ti Pt Cu substitution became more ductile with the increase in concentration. Zr x x 50 50-x x and Hf substitution became more ductile at higher compositions (31.75 – 43.75 at.%). The Ru and Hf substitutions have potential to be used for high-temperature applications. 1. Introduction Shape memory amalgams (SMAs) that display shape memory impact over 373 K can possibly be utilized for higher temperature application, for example, air ship turbine motors, high-temperature actuators, thermal security, and so forth. [1]; these are known as high-temperature shape memory alloys (HTSMAs). Of all the known SMA pieces, the NiTi compound framework has been examined most broadly and is utilized in the best number of business applications. This alloy exhibits strong shape memory effect (SME), and pseudoelastic behavior under the right conditions, which makes this material ideal for a variety of applications [2]. HTSMAs are produced by adding the ternary (third elements) such as Pd, Pt, Hf, Au, and Zr to NiTi for whose temperature can be shifted anywhere between 373 and 973 K [3]. Some of these materials were reported to effectively increase the transformation temperature of NiTi [4]. Hafnium and Zr addition to NiTi has also been investigated due to their lower cost [5]. (Ti Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1 Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 + Hf, Zr) - rich NiTi amalgams have weaknesses, for example, an enormous warm hysteresis, poor thermal steadiness, and fragility [6]. On the other hand, equiatomic TiPt exhibits martensitic phase transformation above 1200 K, ~400K higher than equiatomic TiAu and ~500K higher than equiatomic TiPd [7, 8]; these are categorized as HTSMAs due to their thermo-elastic B2 martensitic phase transformation to B19 above 700 K [1, 9, 10]. It was also found that TiPt alloys exhibited negligible SME (11%), due to the low critical stress for slip deformation compared to the stress required for martensitic reorientation [11]. Yoko Yamabe- Mitarai and co-workers [12] additionally detailed that Ti – 50Pt displayed a solitary yielding marvel and low quality (~450MPa) in martensite and exceptionally low quality (~20 MPa) in the B2 area. Equiatomic Equiatomic TiPt displayed thermo-flexible martensitic phase change, and may not be utilized for high-temperature shape memory materials applications, because of irrelevant SME and low reinforcing in the austenite region. Otherwise, if the shape memory properties can be improved, the B2 phase could be utilized for higher temperature applications [13, 14]. However, research on TiPt enhancement with Zr and Ru partial substitution were discovered powerful for improving the high- temperature quality and shape memory properties, bringing about an expansion in critical stress for slip disfigurement [14]. Cobalt addition was reported to stabilize the B2 phase at lower temperatures and reduced the martensitic transformation temperature due to higher values of tetragonal shear modulus (C′) [15]. Furthermore, it is important to strengthen both martensite and austenite phase against deformation, which is significant for the development of SMAs for high-temperature actuator applications [16]. In the previous work, the effect of a third element Ru, Co, Cu, Zr and Hf on the B19 Ti Pt M was 50 50-x x investigated for x=5 and Ru addition was more effective and preferred for high-temperature shape memory alloys [17]. It has been suggested that Ru and Cu are preferential for Pt substitution, while Zr and Hf showed promising shape memory trends when substituted for Ti site [18] In this study we investigated the thermodynamic and elastic properties of the B2 ternary Ti Pt M M=Ru and Cu and 50 50-x x Ti M Pt M=Zr and Hf shape memory alloys by employing the first principles method for 50-x x 50 understanding their martensitic transformation behavior and mechanical properties. 2. Methodology We employed the first principles density functional theory (DFT) in the Vienna ab initio Simulation Package (VASP) code [19, 20] with the projector augmented wave (PAW) [21]. An energy cut–off of 500 eV was used, to achieve a good convergence of the parameters. We used the generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional [22]. The Brillouin zone integrations were performed with a k-spacing of 0.25 according to Monkhorst and Pack [23]. A 2×2×2 supercell of TiPt was used to substitute a portion of the Pt with Ru and Cu, and Ti with Zr and Hf. 3. Results and Discussion 3.1. Structural and Thermodynamic Properties The calculated equilibrium lattice parameters of the B2 Ti Pt M where M=Ru and Cu are shown in 50 50-x x Figure 1 (a), B2 Ti50-xMxPt50 M=Zr and Hf in Figure 1 (b) (x=6.25, 18.75, 25, 31.75, and 43.75), where a = b = c. The lattice parameters decreased with increased Ru and Cu content with Ti Pt Ru having 50 6.25 43.75 the lowest value of lattice parameter at a=3.085 Å. Conversely, Ti Zr Pt and Ti Hf Pt 50-x x 50 50-x x 50 substitutions increased with an increase in Zr and Hf content, Ti Hf Pt being the lowest at a=3.304 43.75 6.25 50 Å. Figure 1 (c) and (d) show the densities of Ti Pt M where M=Ru and Cu and Ti M Pt M=Zr and 50 50-x x 50-x x 50 Hf against composition. The density of the Ti Pt Ru and Ti Pt Cu substitutions decreased with 50 50-x x 50 50-x x increase in Ru and Cu content, which was also verified by the lattice parameters, this might be due to their atomic radius of Ru and Cu being less than that of Pt. So partial substitution of Pt on Ti Pt M 50 50-x x with Ru was expected to decrease the density of the TiPt alloy [24]. Ti Pt Cu was found to have 50 6.25 43.75 2 Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 the lowest density. On the contrary, Ti Hf Pt increased as 43.75>x>6.25, Ti Zr Pt was observed 50-x x 50 50-x x 50 with a minimal increase with an increased Zr composition. It can also be seen that the atomic radii of Zr and Hf are much greater than both Ti and Pt, resulting in greater densities on the ternary alloys. 3.18 3.36 (b) (a) Ti Pt Ru 3.34 50 50-x x Ti Zr Pt 50-x x 50 Ti Pt Cu 50 50-x x 3.16 3.32 3.30 3.14 3.28 Ti Hf Pt 50-x x 50 3.26 3.12 3.24 3.22 3.10 3.20 3.08 3.18 0 10 20 30 40 0 10 20 30 40 Ti Pt M (M=Ru and Cu) Ti M Pt (M=Zr and Hf) 50 50-x x 50-x x 50 13 17 (c) (d) Ti Hf Pt 12 50-x x 50 Ti Pt Ru 50 50-x x Ti Pt Cu 50 50-x x Ti Zr Pt 50-x x 50 6 12 0 10 20 30 40 0 10 20 30 40 Ti Pt M (M=Ru and Cu) Ti M Pt (M=Zr and Hf) 50 50-x x 50-x x 50 Figure 1. Equilibrium lattice parameters of (a) Ti Pt M (M=Ru and Cu) (b) Ti M Pt (M=Zr 50 50-x x 50-x x 50 and Hf) and densities of (c) Ti Pt M (M=Ru and Cu) (d) Ti M Pt (M=Zr and Hf) ternaries, 50 50-x x 50-x x 50 43.75>x>6.25. The heats of formation (ΔH ), of the intermetallic phase were calculated according to the relation [25]: 𝑡𝑃𝑇𝑖 ∆𝐻 = 𝐸 −[(1−𝑥 )𝐸 +𝑥 𝐸 ], 𝑓 𝑑𝑙𝑖𝑜𝑠 𝑑𝑙𝑖𝑜𝑠 (1) 𝑡𝑃𝑇𝑖 where 𝐸 , 𝐸 and 𝐸 are the total energies of an intermetallic compound, and basic Ti and Pt 𝑑𝑙𝑖𝑜𝑠 𝑑𝑙𝑖𝑜𝑠 in their particular ground-state crystal structures, while x and 1-x allude to the fragmentary convergences of the constituent components. The predicted heats of formation for Ti50Pt50-xMx where M=Ru and Cu and Ti50-xMxPt50 M=Zr and Hf are shown in Figure 2. The heats of formation suggest that the small composition of Ti Pt Ru (– 50 43.75 6.25 0.748 eV/atom) and Ti Pt Cu (–0.693 eV/atom) are more stable; as the Cu content is increased 50 43.75 6.25 the Ti Pt Cu became unstable. Ru is more stable than Cu substitution on Ti Pt M . On the 50 50-x x 50 50-x x contrary, Ti Zr Pt (–0.908 eV/atom) and Ti Hf Pt (–0.966 eV/atom) suggest that they are 6.25 43.75 50 6.25 43.75 50 more stable substitutions. Ti Zr Pt and Ti Hf Pt became more stable when their concentration 50-x x 50 50-x x 50 was increased and Hf substitution became more stable. Density (Mg/m ) Lattice parameters (Å) Density (Mg/m ) Lattice parameters (Å) 𝑃𝑡 𝑇𝑖 𝑃𝑡 𝑇𝑖 Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 -0.1 -0.76 -0.78 (a) (b) -0.2 Ti Pt Cu 50 50-x x -0.80 -0.82 -0.3 -0.84 Ti Zr Pt -0.4 50-x x 50 -0.86 -0.88 -0.5 -0.90 -0.6 -0.92 -0.94 Ti Pt Ru 50 50-x x Ti Hf Pt -0.7 50-x x 50 -0.96 -0.8 -0.98 0 10 20 30 40 0 10 20 30 40 Ti Pt M (M=Ru and Cu) Ti M Pt (M=Zr and Hf) 50 50-x x 50-x x 50 Figure 2. Heats of formation of (a) Ti Pt M (M=Ru and Cu) (b) Ti M Pt (M=Zr and Hf), where 50 50-x x 50-x x 50 43.75 >x>6.25 3.2. Elastic Properties The accurate calculation of elasticity is vital for picking up knowledge into the mechanical stability and elastic properties of compounds. The elastic constants of a cubic crystal have three (C , C , and C ) 11 22 44 independent elastic constants. Applying two sorts of strains (ε1 and ε4) on the cubic system give stresses identifying with three flexible coefficients, yielding a proficient technique for obtaining elastic constants. This technique has been effectively used to study the elastic properties of a scope of materials including metallic frameworks [26]. For a cubic crystal, the mechanical stability conditions are given by [27]. C >0, C >0, + C >|C | and C +2C >0, 11 44 11 12 11 12 (2) The elastic constants were evaluated to observe the impact of ternary substitution Pt with Ru and Cu, and Ti with Zr and Hf. All the independent elastic constants C , C , and C for Ti Pt M where 11 12 44 50 50-x x M=Ru and Cu and Ti M Pt M=Zr and Hf were positive which indicated mechanical stability of the 50-x x 50 structures. The C >C at 25 at.% and 43.75 at.% for Ti Pt Ru in Figure 3 (a), C >C at 18.75– 11 12 50 50-x x 11 12 43.75 at.% for Ti Pt Cu in Figure 3(b), C >C at Ti Zr Pt in Figure 3 (c), and C >C at 25– 50 50-x x 11 12 6.25 43.75 50 11 12 43.75 at.% for Ti50-xHfxPt50 in figure 3 (d), which contributed to positive C′. However, the C44 increase minimally with increase in Ti Pt Ru and Ti Pt Cu substitutions, suggesting a good correlation 50 50-x x 50 50-x x between C and C′ moduli, while decreasing minimally for Ti Zr Pt and Hf substitution. The 44 50-x x 50 positive shear suggests that all the ternary compositions above satisfied all conditions of mechanical stability of the cubic crystal. 400 220 200 (b) (a) C 300 11 200 120 100 C 60 C 0 10 20 30 40 0 10 20 30 40 Ti Pt Ru 50 50-x x Ti Pt Cu 50 50-x x C , C and C (GPa) 11 12 44 Heats of formation (H ) C , C and C (GPa) 11 12 44 Heats of formation (H ) f Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 220 250 (c) (d) 180 200 160 12 140 150 100 100 60 50 20 0 0 10 20 30 40 0 10 20 30 40 Ti Zr Pt Ti Hf Pt 50-x x 50 50-x x 50 Figure 3. Independent elastic properties C (C , C , and C ) (GPa) of (a) Ti Pt Ru (b) Ti Pt ij 11 12 44 50 50-x x 50 50- Cu (c) Ti Zr Pt (d) Ti Hf Pt , where 43.75>x>6.25 x x 50-x x 50 50-x x 50 The Ru and Cu substitution became mechanically stable with an increase in content, 25 – 43.75 at.% Ru and Cu from 18.75 at.% as shown in Figure 4 (a), Zirconium substitution stabilizes around 43.75 at.%, whilst Hf from 25 at.% in Figure 4 (b). The C′ increases with increase in Ru, Cu, Zr, and Hf content, it is also observed that smaller C′ values lead to larger anisotropy (A). These suggest that the Group 4 substitution stabilizes with an increase in Zr and Hf content, Ru belongs to Group 8, a similar trend was observed with the heats of formation; this might be due to Ru having a lower atomic radius than both Ti and Pt. Ti50Pt50-xCux in Figure 4 (a) stabilized around 18.75 at.% and it also noted that Cu has an atomic radius less than that of Pt, hence the observed curve. Furthermore, Ru substitution reduced the martensitic transformation temperature of TiPt [14] more than Ti Pt Cu , indicated by higher C′, which is consistent with the experimental findings at lower 50 6.25 43.75 concentrations for Ru substitution. The C′ moduli of Ti Pt Ru correspond with A of 0.78, closer 50 6.25 43.75 to unity (A≈1) [28]. The Hf substitution in Figure 4 (b) increased the martensitic transformation temperature of the Ti Pt since it gave the lowest C′ at 6.25 at.%, with an A value of 0.87. The Bulk 50-x 50 modulus (B) measures the level of firmness, or the energy required to deliver a given volume disfigurement [29]. In Figure 4 (c), Bulk moduli for Ti Pt Ru increased with an increase in Ru 50 50-x x content, suggesting that the structure became more hardened, while Ti Pt Cu decreased with 50 50-x x increased Cu content, suggesting that it became less hardened. Ti Zr Pt and Ti Hf Pt in Figure 4 50-x x 50 50-x x 50 (d) both decreased with increase in Zr and Hf content. These suggest that to maintain the hardness of Ti Pt Ru can be used with higher substitutional content, while Ti Pt Cu , Ti Zr Pt , and Ti 50 50-x x 50 50-x x 50-x x 50 50- Hf Pt may have to be used at smaller substitutional content. x x 50 120 40 100 (a) (b) Ti Zr Pt 50-x x 50 -20 Ti Pt Cu 50 50-x x -40 -20 Ti Hf Pt 50-x x 50 -40 -60 Ti Pt Ru 50 50-x x -60 -80 -80 0 10 20 30 40 0 10 20 30 40 Ti M Pt (M=Zr and Hf) 50-x x 50 Ti Pt M (M=Ru and Cu) 50 50-x x C , C and C (GPa) 11 12 44 C' (GPa) C , C and C (GPa) 11 12 44 C' (GPa) Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 220 190 (c) (d) Ti Pt Ru 50 50-x x 200 Ti Hf Pt 186 50-x x 50 Ti Zr Pt 140 Ti Pt Cu 50-x x 50 50 50-x x 0 10 20 30 40 0 10 20 30 40 Ti M Pt (M=Zr and Hf) Ti Pt M (M=Ru and Cu) 50-x x 50 50 50-x x Figure 4. Shear moduli C′ (GPa) for (a) Ti Pt M (M=Ru, Cu) (b) Ti M Pt (M=Zr and Hf) and 50 50-x x 50-x x 50 their Bulk moduli (B) (a) Ti Pt M (M=Ru and Cu) (b) Ti M Pt (M=Zr and Hf). 50 50-x x 50-x x 50 According to Pugh, for metals to be considered ductile the Bulk to shear B/G ratio must be >1.75, otherwise, the metal is brittle [30]. In Figure 5 (a), the structures displayed ductility with an increase in Ru and Cu content, since the B/G >1.75. A similar trend was observed in Ti substitution with Zr and Hf in Figure 5 (b), and the dip on Zr 25 at.% was caused by lower values of G. Lower atomic percentages (6.25 at.%) for (Pt with Ru and Cu, Ti with Zr and Hf) were attributed to negative B/G ratio, which did not satisfy ductility conditions. Therefore, Ru at 6.25–18.75 at.%, Cu at 6.25 at.%, Zr at 6.25–25 at.%, and Hf at 18.75 at.% were brittle. 40 30 (b) (a) Ti Hf Pt 50-x x 50 30 20 Ti Pt Ru 50 50-x x 20 Ti Zr Pt 50-x x 50 Ti Pt Cu 50 50-x x -10 -10 -20 0 10 20 30 40 0 10 20 30 40 Ti Pt M (M=Ru and Cu) Ti M Pt (M=Zr and Hf) 50 50-x x 50-x x 50 Figure 5. B/G ratio for (a) Ti Pt M (M=Ru and Cu) (b) Ti M Pt (M=Zr and Hf), where 50 50-x x 50-x x 50 43.75>x>6.25. 4. Conclusions A computational modelling study on the thermodynamic and mechanical properties in Ti Pt M 50 50-x x (M=Ru and Cu) and Ti M Pt (M=Zr and Hf) where 0<x<50 was performed. The effect of the lattice 50-x x 50 parameter depends on the type of the alloying element and sub-lattice. The Ru and Cu showed a decrease in lattice parameter, while Zr and Hf show an increase. The thermodynamic stability for the ternary framework was explored by somewhat substituting a portion of the Pt with Ru and Cu, and Ti with Zr and Hf, we observed that Ru (–0.748 eV/atom) at 6.25 at.% and Hf (–0.966 eV/atom) at 43.75 at.% substitutions were the most stable structures. The elastic constant of both for Pt substitution and Ti substitution were found to be stable with all the moduli obeying the elastic stability criterion. The addition of Ru and Cu content in Pt and Zr and Hf in Ti increased C′ moduli of the cubic phase leading to a positive anisotropy. Ti Pt Ru and Ti Hf Pt increases the transformation temperature. This 50 50-x x 50-x x 50 demonstrated Ru having a place with Group 8 of the Periodic Table go about as B2 phase stabilizer than Cu in Pt substitution, followed by Hf in Ti substitution. Bulk Modulus B (GPa) B/G ratio Bulk Modulus B (GPa) B/G ratio Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 Acknowledgements The simulations were completed utilizing computer resources at the Materials Modelling Centre (MMC) at the University of Limpopo and the Centre for High Performance Computing (CHPC) in Cape Town. The authors recognize the South African Research Chair Initiative of the Department of Science and Technology and the National Research Foundation is profoundly perceived. References [1] Ma J, Karaman I and Noebe R D 2010 High temperature shape memory alloy Int. Mater. Rev. 55 [2] Kumar P K and Lagoudas D C 2008 Introduction to shape memory alloys Modeling and Eng. Application Lett. 11 [3] Funakubo H (Ed.), 1987 Shape Memory Alloys, Gordon and Breach Science Publishers [4] Suzuki Y, Xu Y, Morito S, Otsuka K and Mitose K 1998 Effects of boron addition on microstructure and mechanical properties of Ti–Td–Ni high-temperature shape memory alloys Mater. Lett. 36 85 [5] Carl M, Smith J D, Van Doren B and Young M L 2017 Effect of Ni-content on the transformation temperatures in NiTi-20 at. % Zr high temperature shape memory alloys Metals 7 511 [6] Hsieh S F, Wu S K 1998 Memory alloys a study on ternary Ti–rich TiNiZr shape memory alloys Mater. Charact. 41 151 [7] Donkersloot H C and van Vucht J H N 1970 Martensitic transformations in gold-titanium, palladium-titanium and platinum-titanium alloys near the equiatomic composition J. Less- Common Metals. 20 83 [8] Kawamura T, Tachi R, Inamura T, Hosoda H, Wakashima K, Hamada K and Miyazaki S 2006 Effects of ternary additions on martensitic transformation of TiAu Mater. Sci. Eng. A438 383 [9] Otsuka K, Oda K, Ueno Y, Piao M, Ueki T and Horikawa H 1993 The shape memory effect in a Ti Pd alloy Scripta Metall. Mater. 29 1355 50 50 [10] Yamabe-Mitarai Y, Arockiakumar R, Wadood A, Suresh K S, Kitashima T, Hara T, Shimojo M, Tasaki W, Takahashi M, Takahashi S and Hosoda H 2015 Ti(Pt, Pd, Au) based high temperature shape memory alloys in Materials Today: Proceedings 2 S517–S522 [11] Yamabe-Mitarai Y, Hara T, Miura S and Hosoda H 2010 Shape memory effect and pseudoelasticity of TiPt Intermetallics 18 2275 [12] Yamabe-Mitarai Y, Hara T, Miura S and Hosoda H 2006 Mechanical properties of Ti–50(Pt,Ir) high-temperature shape memory alloys Materi. Trans. 47 650 [13] Mahlangu R, Phasha M J, Chauke H R, Ngoepe P E 2013 Structural, elastic and electronic properties of equiatomic PtTi as potential high-temperature shape memory alloy Intermetallics 33 27 [14] Wadood A, Takahashi M, Takahashi S, Hosoda H and Yamabe-Mitarai Y 2013 High-temperature mechanical and shape memory properties of TiPt–Zr and TiPt–Ru alloys Mater. Sci. Eng. A564 34 [15] Mahlangu R 2015 Computational modelling studies of Ti Pt M (M: Co, Ni, Pd, Ir) shape 50 50-x x memory alloys. University of Limpopo: Thesis [16] Noebe R, Gaydosh D, Padula S, Garg A, Biles T, Nathal M. 2005 Properties and potential of two (Ni, Pt)Ti alloys for use as high-temperature actuator metals Proc. SPIE Int. Symp. Smart Struct. Mater. 5761 364 [17] Mashamaite M P, Chauke H R and Ngoepe P E 2018 Mechanical properties and stability of TiPt- M (M=Ru, Co, Cu, Zr and Hf) for high temperature applications IOP Conf. Ser.: Mater. Sci. Eng. 430 012019 [18] Bozzolo G, Mosca H O and Noebe R D 2007 Phase structure and site preference behavior of ternary alloying additions to PdTi and PtTi shape-memory alloys Intermetallics 15 901 [19] Hohenberg P and Kohn W 1964 Inhomogeneous electron gas Phys. Rev. B. 136 864 [20] Kohn W and Sham L J 1965 Self-consistent equations including exchange and correlation effects 7 Conference of the South African Advanced Materials Initiative (CoSAAMI 2019) IOP Publishing IOP Conf. Series: Materials Science and Engineering 655 (2019) 012011 doi:10.1088/1757-899X/655/1/012011 Phys. Rev 140 A1133 [21] Blöchl P E 1994 Projector augmented-plane wave method Phys. Rev. B. 50 17953 [22] Perdew J P, Burke K and Ernzerhof M 1996 Generalized gradient approximation made simple Phys. Rev. Lett. 77 3865 [23] Monkhorst H J and Pack J D 1976 Special points for Brillouin-zone integrations Phys. Rev. B. 13 [24] Wadood A and Yamabe-Mitarai Y 2014 TiPt–Co and TiPt–Ru high temperature shape memory alloys Mater. Sci. Eng. A601 106 [25] Fernando G W, Watson R E and Weinert M 1992 Heats of formation of transition-metal alloys: Full-potential approach and the Pt-Ti system Phys. Rev. B. 45 15 8233 [26] Zhang J M and Guo G Y 1997 Microscopic theory of the shape memory effect in TiNi Phys. Rev. Letters 78 4789 [27] Mehl M J and Klein B M 1994 First principles calculations of elastic properties of metals Inter. Comp. 1 1 [28] Goumri-Said S and Kanoun M B 2007 Theoretical investigations of structural, elastic, electronic and thermal properties of damiaoite PtIn Comp. Mat. Sci. 43 243 [29] Kittle C 1976 Introduction to solid state physics, 5th ed., New York: John Wiley & Sons [30] Pugh S F 1954 Relations between elastic moduli and plastic properties of polycrystalline pure metals Philos. Mag 45 843

Journal

IOP Conference Series Materials Science and Engineering – IOP Publishing

Published: Oct 1, 2019

There are no references for this article.