Novel Shape Memory Alloys: Poster Session
Program Organizers: Othmane Benafan, NASA Glenn Research Center

Tuesday 5:30 PM
July 11, 2017
Room: Crystal Ballroom A
Location: Hyatt Regency Chicago

P2-24: Aging Hardening Behaviors in Bcc-type Mg-Sc Alloy: Daisuke Ando1; Yukiko Ogawa1; Yuji Sutou1; Junichi Koike1; 1Tohoku University
     Recently, our group discovered that a metastable bcc Mg-Sc alloy shows a shape memory behavior due to martensitic transformation [1]. This discovery was led by a finding of very fine plate-like precipitates in bcc-type Mg-Sc alloy after aging. According to a Mg-Sc binary phase diagram, we could expect a metastable bcc phase transform to a stable hcp phase in low annealing temperature. Then, we recognized that the microstructure is much resemblance to that of Ti based shape memory alloy after aging. Therefore, we researched the alloy with considerable certainty that Mg-Sc alloys show shape memory effect. In this presentation, we would like to discuss the aging hardening behavior in bcc-type Mg-Sc alloy in detail.[1] Y. Ogawa, D. Ando, Y. Sutou, J. Koike Science, 353 (2016) 368-370

P2-25: An Experimental Study on Strain Rate Sensitivity of Fe-28Mn-6Si-5Cr Shape Memory Alloy under Tensile Deformation: Bo Cao1; Takeshi Iwamoto1; 1Hiroshima University
    Fe-28Mn-6Si-5Cr alloy, which is one of Fe-based shape memory alloys, shows the smaller shape memory effect (SME) compared with the widely-used Ni-Ti alloy. However, its production cost is much lower. Thus, the alloy is attempted to be applied to many engineering fields under different working environment loaded at various strain rates. It is necessary to evaluate tensile deformation behavior of the alloy in a wide range of strain rate including a measurement of an amount of martensite which can control such excellent performances as well as temperature for increasing a reliability of the alloy. In this study, tensile tests at various maximum strain are conducted from quasi-static to impact deformation. The rate sensitivity of volume resistivity and temperature in the alloy is estimated experimentally by using the assembled circuit of Kelvin double bridge with a higher precision and a thermocouple during tensile tests.

P2-26: Characterization of new Cu-based Shape Memory Alloys with very low transformation temperature: Patricia Lorenzo Garcia-Minguillán1; Iñaki López Ferreño1; Tomasz Breczewski1; Maria L. Nó1; Jose San Juan1; 1University of Basque Country
     New Cu-based SMAs have been developed for cryogenic applications, these alloys have a temperature range between 20-400 K. Unfortunately, most of the commercial experimental equipment are usually working in temperature ranges down to about 100K.So in the present work, we describe first the design of a new electrical resistivity equipment with a closed cycle, based on four probe method, in order to measure the transformation temperatures down to liquid helium. The final operational performances are also described. Then in the second part of the work, we used this equipment to study a new family alloy exhibiting martensitic transformation at very low temperatures, down to 20 K. The dependence of the transformation temperatures on concentration is established. In the intermediate temperature range, resistivity results have been compared with those obtained by DSC in order to verify the reliability of all transformation temperatures range in these new alloys.

P2-27: Cryogenic Immersion Time Influence on Thermal and Mechanical Properties of a Ni48Ti52 Shape Memory Alloy: Bartholomeu Cruz Filho1; 1Universidade de Brasília - UnB
    ABSTRACT: Cryogenic processing has been used with relative success to increase the wear resistance of tool steels and high cycle fatigue life in ferrous materials. This study investigates the effects of cryogenic immersion on thermal and mechanical properties of an alloy with Ni48Ti52 shape memory. The treatments consist of a cryogenic cooling 24°C to -196°C with a heating and cooling rate of 18°C/h, the samples immersed for 12 hours, 18 hours and 24 hours at a temperature of -196 °C, respectively. The modulus of elasticity and damping obtained by the pulse excitation technique, the phase transformation temperature, latent heat of transformation obtained by differential scanning calorimetry and hardness C scale obtained by Hockwell a comparative analysis of the properties of their respective CP'S with and without DCT were performed using optical microscopy testing procedures, scanning electron microscopy and diffraction X-ray which allowed to assess how these properties they are affected. The results showed that cryogenic treatment affects all the properties investigated, with emphasis on reducing the latent heat of transformation and increased damping factor. Microstructural analysis indicates that these changes may be associated with changes in grain size and Ti2Ni precipitates.

P2-28: Crystallization and Martensitic Transformation Behavior of Ti-Ni-Si Alloys: Ju-wan Park1; Yeon-min Im1; Yeon-wook Kim2; Tae-hyun Nam1; 1Gyeongsang National University; 2Keimyung University
    Ti-Ni-Si alloy ribbons were prepared by melt spinning and then crystallization temperature and activation energy for crystallization were investigated by differential scanning calorimetry(DSC). Crystal structure and microstructures of ribbons was examined by X-ray diffraction and electron microscopy. Ti-Ni-Si alloy ribbons with Si content less than 1.0 at% were crystalline, while those more than 3.0 at% were amorphous. Crystallization occurred in the sequence of amorphous → Ti2Ni + B2 → Ti2Ni + B2 + TiNi3 → Ti2Ni + B2 + TiNi3 + TiSi + Ti5Si4. Activation energy for crystallization was 189±8.6 kJ/mol for a Ti-47Ni-3Si alloy and 212±8.6 kJ/mol for a Ti-45Ni-5Si alloy. In a Ti-47Ni-3Si alloy, the B2-B19’ transformation occurred irrespective of crystallization temperature. In a Ti-45Ni-5Si alloy, the two-stage B2-R-B19’ transformation occurred when crystallization temperature was higher than 973 K, while the one-stage B2-R when it was lower than 893 K.

P2-30: Design of Fatigue-Resistant Shape Memory Alloys for Medical Applications: Chuan Liu1; Gregory Olson1; 1Northwestern University
    NiTi-based shape memory alloys have been widely applied in biomedical devices. While low Ni composition is desirable to decrease Ni-hypersensitivity, long fatigue life is also of essential importance to fulfill new stringent performance requirements of artificial heart valve. Fatigue simulations modeling crack nucleation have identified the significance of increasing matrix yield strength and controlling inclusion size. The precipitation of coherent nanoscale L21 Heusler aluminides from a supersaturated B2 matrix is an effective approach to enhance its matrix yield strength. A system design approach is taken to develop high strength NiTi-based alloys with quaternary additions such as Pd and Zr. To control inclusion size, inclusion morphologies of NiTi tubes processed by different melting methods are characterized. Electron beam refining is confirmed to significantly decrease the average inclusion size.

P2-31: Effect of Magnetron Sputtered W Thin Film on the Surface Characteristics and Corrosion Behavior of NiTi Shape Memory Alloys: Ailian Liu1; Jiawen Xu1; Chao Liu2; Jiehe Sui3; 1Heilongjiang University of Science and Technology; 2 Northeast Petroleum University; 3Harbin Institute of Technology
    NiTi shape memory alloys have been widely applyed in the medical field due to their unique shape memory effect and superelasticity as well as biocompatibility. However, excesses of Ni ion may cause allergic reactions and promote carcinogenesis and toxic reactions. Surface modification of NiTi is an effective way to improve the above problems. W thin film was deposited on NiTi alloy by magnetron sputtering in this paper and the surface characteristics and corrosion behavior of experimental alloys were researched. Results show that the W film with sputtering power 100W is uniformly dense, with the minimum roughness and maximum thickness. Sputtering W leads to the formation of W2O5 and inhibits the release of Ni ion effectively. The corrosion resistance of NiTi alloy in Hank's solution has been evidently improved by W sputtered. The NiTi alloy with a moderate magnetron sputtering power 100W exhibits the best corrosion resistance ability.

P2-32: Effect of Silver Addition on the Microstructure, Cytotoxicity and Corrosion Resistance of NiTi and NiTiCu Shape Memory Alloys: Prasanna Iyengar1; Sampath Vedamanickam1; 1Indian Institute of Technology, Madras
     Among shape memory alloys (SMAs), Ni-Ti SMAs are extensively for medical devices. Though addition of silver enhances biocompatibility and antibacterial behaviour, it has not been explored on Ni-Ti alloys. In the present work, NiTiAgx and NiTiCuyAgx alloys were therefore prepared by vacuum induction melting, homogenized and rolled at 900ºC. Cytotoxicity was assessed by MTT assay using L6 myoblast cells and binary NiTi as positive control. The transformation temperatures were determined by DSC. Phase analysis was carried out by XRD and Rietveld method was used to refine data to obtain information on crystal structure and strain parameters. Corrosion studies were carried out on the alloys in Hank’s solution. SEM and EDX were used to characterize the microstructures and morphological changes during the assay. The results were correlated to assess the effect of addition of Ag on the properties of the NiTi alloys. Keywords: shape memory alloys, biocompatibility, cytotoxicity, MTT assay, corrosion,

P2-33: Effect of Testing Temperature on Deformation Behavior of a Ti-Au-Cr-Zr Superelastic Alloy : Yuri Shinohara1; Masaki Tahara1; Tomonari Inamura1; Hideki Hosoda1; 1Tokyo Institute of Technology
     A metastable β (bcc) Ti-Au-Cr-Zr alloy exhibits superelasticity at wide temperature range compared to conventional β-Ti alloys. Testing temperature dependence on microstructure and superelastic properties were revealed in this study to understand the mechanism of superelasticity of this alloy. Ti-4Au-5Cr-8Zr (mol %) was analyzed by transmission electron microscopy (TEM) observations at 93 - 297 K. In addition, the mechanical properties of this alloy were evaluated by tensile tests at 123 - 433 K. The fundamental reflection of β phase and diffuse scattering of athermal ω phase were recorded regardless of the testing temperature in selected area diffraction pattern. The yield stress was dependent on testing temperature as shown by the linear relationship with positive slope at 313 - 413 K. It is considered that the yield stress corresponds to stress for inducing martensite and follows Clausius-Clapeyron relationship at this temperature range.

P2-34: Effect of Thermal Cycle on Shape Memory Characteristics of Ti-(50.0, 50.3)Ni-(15-X)Hf-XZr Alloys: Jae Il Kim1; Aaron Stebner2; Ik Ha1; 1Dong-A University; 2Colorado school of mines
    This study investigated the effect of theraml cycle on tranformation temeprature of Ti-[50.0, 50.3]Ni-(15-X)Hf-XZr(X=0~15). After melting, all ingots were homogenized at 1273K for 10hr in an argon atmosphere, followed by solution treatment at 1073K for 1hr and water quenching. Thermal cycle(~1000th) without loadong was carried out. As a result of DSC measurement with increasing Zr content, the martensitic transformation temperature(Ms) of Ti-(50.0, 50.3)Ni-(15-X)Hf-XZr alloys decreased. The Ms of Ti-50.0Ni-(15-X)Hf-XZr alloy is higher than that of Ti-50.3Ni-(15-X)Hf-XZr alloys in same Zr content. The Ms of Ti-50.3Ni-(15-X)Hf-XZr steeply decrease than Ms of Ti-50.0Ni-(15-X)Hf-XZr. With increasing thermal cycle(~1000th), the Ms decreases and saturates in low Zr conten alloys and decreases continuously in the high Zr content alloys. This means that the addition of Zr causes thermal stability to degrade. The Ms of Ti-50.0Ni-Hf alloys decrease more than that of Ti-50.3Ni-Hf alloys with increasing thermal cycle number at the same Zr content.

P2-35: Effects of Ageing on the Superelastic Properties of 50.3Ni-Ti-XHf (x = 6,8) Alloys: Joseph Pauza1; Aaron Stebner1; Jaeil Kim2; Tom Duerig3; Spencer Connor1; 1Colorado School of Mines; 2University of Dong-A; 3Confluent Medical
    Traditional Nitinol alloys require a significant amount of cold-work in order to obtain strengths exhibited by precipitate hardened NiTiHf alloys. As a result, new NiTiHf alloys have been developed for 3D printing applications, where cold-work is not practical. We present an investigation of the effects of H-phase precipitation on the superelastic behavior of NiTiHf6 and NiTiHf8 as a result of variations in ageing treatments. In Nitinol alloys it is clear that the increase in precipitate volume increases the transformation temperatures, however the effect of precipitate growth on the transformation temperatures of these novel alloys is not as straightforward. Hafnium acts as transformation temperature promoter while Nickel is a demoter and H-phase precipitate depletes the matrix of both elements, consequently it is unclear how different precipitate growth will influence the transformation stresses seen in these novel alloys. We present an evaluation of these effects using mechanical testing, DSC, and microstructure analysis.