THERMEC 2006

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Authors: Tae Hyun Nam, Cheol Am Yu, Yun Jung Lee, Yinong Liu
Abstract: Shape memory characteristics and superelasticity of an temperature gradient annealing(TGA) treated equiatomic Ti-Ni alloy have been investigated by means of differential scanning calorimetry(DSC), thermal cycling tests under constant load and tensile tests. By annealing 25% cold worked alloy under the temperature gradient from 658 K to 466 K, 7 K variation in TR*and 19 K variation in Ms* were obtained along the length of sample(150mm). Temperature dependence of transformation elongation(dε/dT) of TGA treated Ti-Ni alloy wires was in the range of 0.05 %/K and 0.01 %/K depending on annealing temperature ranges. The dε/dT obtained from TGA treated sample under the temperature gradient from 658 K to 466 K was 0.03 %/K. TGA treated alloy showed the clear superelastic recovery.
3169
Authors: Shozo Inoue, Takahiro Namazu, T. Fujimoto, Keiji Koterazawa, Kanryu Inoue
Abstract: The purpose of this work is to quantitatively clarify the shape memory behavior of Fe-Pd films containing ~30at%Pd by thermal cycling testing under various constant stresses. Fe-Pd films (4 $m thick) were deposited onto Si wafers with thermally formed 1$m-thick SiO2 layer using a dual-source dc magnetron sputtering apparatus. The deposited films were all annealed at 900°C for 60 min followed by iced water quenching. Perfect shape recovery was observed for Fe-30.0at%Pd film when the applied stress was lower than 300 MPa. The maximum recoverable strain was ~0.6%. Fe-29.2at%Pd film, on the other hand, showed unrecovered strain after thermal cycling even if the applied stress was 40 MPa. XRD measurements of the Fe-29.2at% Pd film before and after thermal cycling revealed irreversible fcc-bct martensitic transformation that occurred during cooling process at a temperature around -80°C. The critical stress of Fe-Pd films, at which plastic deformation commences to occur, is higher for films with 30 at% Pd than for films with 29.2 at% Pd, which is practically advantageous. The Ms temperature of these films is lower than room temperature when no bias stress is applied, while it becomes higher than room temperature when appropriate bias stress is applied, obeying Clapeyron-Clausius law.
3173
Authors: Bong-Hwan Kim, Je Sik Shin, Sang Mok Lee, B.M. Moon
Abstract: For the development of an economical production technology of multi-crystalline silicon, an EMCC (Electro Magnetic Continuous Casting) process using a segmented Cu cold crucible was practiced. In order to enhance significantly the heating efficiency of silicon melt keeping non-contact condition during continuous melting and casting processes, the effects of Joule heating and electromagnetic pressure in molten silicon were optimized by systematically varying crucible design and configuration. Throughout the present investigation, multi-crystalline silicon ingot was successfully produced at the casting speed of above 1.5 mm/min under a non-contact condition.
3179
Authors: Satoshi Kishimoto, Norio Shinya
Abstract: Several methods of fabricating metallic closed cellular materials a spark plasma sintering (SPS) system have been developed. Powdered polymer particles coated with a nickel-phosphorus alloy layer using electro-less plating were pressed into pellets and sintered at high temperatures in a furnace using SPS system. Metallic closed cellular materials containing different materials from the cell walls were then fabricated. The physical, mechanical and damping properties of these materials were measured. The results of the compressive tests show that this material has different stressstrain curves among the specimens that have different cell wall thicknesses and the sintering temperatures of the specimens affect the compressive strength of each specimen. Also, it seems that the results of the compressive tests show that this material has a high-energy absorption. The internal friction of this material was measured and the results show that this internal friction is the same as that of pure aluminum. These results suggest that this material can be utilized as an energy absorbing and passive damping material.
3184
Authors: Hiroyuki Nakayama, Minoru Taya
Abstract: Characteristics of high temperature shape memory alloy in Ti50-Pd(50-x)-W(x) at%, x = 3 and 5 system has been examined. The prepared ingot was homogenized at 1273 K for 86.4 ks followed by water quenched. The homogenized samples were hot-rolled at 1273 K to a plate shape with thickness of 3.5 mm and 1.0 mm. Transformation temperatures were determined by 4-probe electrical resistivity measurement. The transformation behavior in the both samples exhibited similar trend. The first heating curve showed no significant step. In contrast, the first cooling curve exhibited clear step due to martensitic transformation. After second cycle, the transformation behavior was stabilized, thus the clear steps in the cooling and heating curves were seen. Stressstrain curve of hot-rolled plate with 3.5 mm was examined by compression in Ti50-Pd47-W3 at% alloys. The sample exhibited 1 % shape memory effect. By bending test, nearly perfect SME effect was observed in hot rolled Ti50-Pd45-W5 at% alloy plate with thickness of 1 mm.
3190
Authors: Chin Jye Yu, Chiang Shu Lei, Rabindra Mahapatra, Jeff Sharp, Ibrahim Karaman
Abstract: In this paper we report the effects of Equal Channel Angular Extrusion (ECAE) processing on the phase transformation characteristics of Ni-Ti based shape memory alloys in terms of transformation temperatures, temperature hysteresis, and microstructural evolution. The ECAE process affects the material’s shape memory behavior via microstructural refinement. Differential Scanning Calorimetry (DSC) and Transmission Electron Microscopy (TEM) were utilized to investigate the effects of microtructural refinement and substructure formation on the shape memory behavior of these alloys. The microstructural refinement was found to have significant influence on the transformation temperatures.
3195
Authors: Hisashi Sato, Seiichiro Umaoka, Yoshimi Watanabe, Ick Soo Kim, Masakazu Kawahara, Masao Tokita
Abstract: Ti and Ti alloys are particularly attractive materials as the metallic implant-material. This is because that these alloys have low shear modulus and the good biological compatibility with bone. However, interfacial adhesion ability of bone and Ti alloy is low. As improvement method of the interfacial adhesion ability, bioaffinity material like hydroxyapatite has been coated on surface of the Ti alloys. However, such bioaffinity materials have low strength and wear resistance. In this study, Ti composites containing biodegradable poly-L-lactic-acid (PLLA) fiber were fabricated by spark plasma sintering (SPS) method. The PLLA fiber plays a role as reinforcement in Ti matrix, and can be gradually decomposed inside body with progress of time. By the decomposition of PLLA, pore is generated in Ti matrix, and bone simultaneously penetrates into the pore. Therefore, tightly bond between bone and Ti matrix can be expected. Using the Ti-PLLA composites fabricated by SPS method, microstructural observation and mechanical tests were performed. It was found that Ti-PLLA composite has laminate-layer structure with plate-like shape PLLA. Hardness and wear behavior of Ti-PLLA composite has anisotropy due to its structure. However, strength of the Ti-PLLA composite is low because of the imperfect sintering of Ti matrix. Since sintering of Ti matrix can be improved by changing the temperature of SPS, Ti-PLLA composite with anisotropic mechanical properties can be expected by SPS method.
3201
Authors: Takahiro Namazu, Y. Okamura, Y. Tashiro, Shozo Inoue
Abstract: This paper describes novel MEMS probe card device, which is composed of silicon (Si) cantilever beams actuated by titanium-nickel (Ti-Ni) shape memory alloy (SMA) films. Since Ti-Ni SMA film can yield a higher work output per unit volume, Ti-Ni film-actuated Si cantilever beam is expected to be a MEMS probe card device providing large contact force between probe and electrode pad. The developed cantilever beam produces a contact force by not only cantilever bending in contact but also the shape memory effect (SME) of Ti-Ni film arising from Joule’s heating. The SME of Ti-Ni film containing Ti of 50.5 atomic (at.) % to 53.2 at. % can generate an additional contact force of 200 μN on average under applying an electric power of 500 mW to the film. Ti-Ni film-actuated Si cantilever beam would be a key element for successful MEMS probe card with larger contact force and smaller size.
3213
Authors: Yukio Makino, T. Yoshioka, H. Saito, Saburo Sano, Jun Akedo, Shoji Miyake
Abstract: Characteristics of heating processing based on millimeter-wave or pulsed high current are discussed from the standpoint of the interaction between electromagnetic energy and solid materials. Capabilities of the electromagnetic processing are indicated by exemplifying several successful results such as millimeter-wave sintering of AlN, millimeter-wave post-annealing of aerosol-deposited PZT films and synthesis of single-phase nano-structured anatase by SPS (or pulsed high current heating). It is shown in these examples that well-characterized properties such as high thermal conductivity and preferential orientation are created by the inherent effect due to the electromagnetic field, which is called microwave or SPS effect in millimeter-wave or SPS processing.
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