PRICM-5

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Authors: Yang Zhou, Hong Xiang Zhai, Zhen Ying Huang, Ming Xing Ai, Zhi Li Zhang, Shi Bo Li, Cui Wei Li
Abstract: Various toughening methods, i.e. partially stabilized zirconia transformation toughening, transformation- SiC whisker reinforcing and transformation-SiC particle reinforcing were used to improve the mechanical properties of alumina ceramic. Influence of various toughening methods on microstructure and mechanical properties of the alumina-matrix composites were studied. On the basis of transformation toughening, by which the strength and toughness of Al2O3 ceramic improved simultaneously, the addition of SiC whisker substantially enhanced the toughness, whereas the addition of SiC particle increased both toughness and strength to a certain degree. Mechanical properties of the testing materials were closely related with their morphologies of fracture surfaces. Toughening mechanisms of the composites were also studied. In the transformation-whisker reinforced composite or the transformation-particle reinforced composite, the two toughening methods affected with each other and produced a cooperative toughening effect.
909
Authors: Fa Zhang Yin, Cheng Chang Jia, Xuezhen Mei, Bin Ye, Yanlei Ping, Xuan Hui Qu
Abstract: The SiCp performing sample was made first then Al/SiCp (65%) was manufactured. Appropriate component and proportion of binder and process parameters were selected to control the porosity. Debinding has succeeded by extractive and thermal debinding processes. SiCp preforming samples with good appearance, enough strength, and right porosity were obtained by pre-sintering process at 1100°C. Composites with high density and homogeneous microstructure were manufactured by pressure infiltration under 1050°C and 15MPa. The distribution of aluminium and silicon elements was homogeneous. The primary components of materials are aluminium, β-SiC and α-SiC. The thermal expand coefficient of composites is 8.0×10-6/°C at room temperature, which increases with temperature and reaches to 11.0×10-6/°C at 300°C. The density is 2.92g/cm3, and relative density is more than 97 %. The strength is about 500MPa, approaching to the upper limit of the theoretical value.
913
Authors: W.L. Zhang, M.Y. Gu, De Zun Wang
Abstract: A squeeze casting 15vol.%SiCw/Al and pure aluminum were cold rolled to 50 pct reduction in thickness and then annealed at 500°C for 1h. The textures of the treated materials were examined using XRD. The dominant texture components in the cold rolled composites consisted of {112}<111>、{100}<011> and {123}<634> and were much weaker than those in the cold rolled aluminum. The new texture components in annealed composites were {211}<213>、{013}<131> and {011}<211> and had the similar intensity as those remained from the deformation state. This indicated that the recovery reaction and recrystallization occurred simultaneously when the cold rolled composite was annealed at 500°C. Also, the annealing texture was much weaker in the composite than that in the aluminum. The weaker deformation and annealing textures in the composites can be attributed to the introduction of the whiskers.
917
Authors: Gen Sasaki, Junichi Adachi, Yong Bum Choi, Jin Pan, Toshio Fujii, Kazuhiro Matsugi, Osamu Yanagisawa
Abstract: In order to infiltrate the molten aluminum alloy to the reinforcement preform by low pressure in casting process and acquire the high performance composites with high density, the effect of the ultrasonic vibration on the infiltration was investigated by model experiments using clear solution and glass or aluminum borate preform, which is correspond to a molten matrix and reinforcement, respectively. Ultrasonic vibration improves the wettability of liquid polyester resin on glass plate, dramatically. The final infiltration height and infiltration speed of liquid polyester resin in glass capillary were improved by the ultrasonic vibration. Furthermore, the infiltration speed of water to aluminum borate preform accelerated by ultrasonic vibration. This effect was more remarkable, when the infiltration height is lower or infiltration time is shorter. In actual, the molten aluminum alloy infiltrate to SiC preform using ultrasonic vibration easily and acquire the high dense composites without pores.
921
Authors: Kenji Wakashima, T. Shimoyamada, H. Noma, Tomonari Inamura, Hideki Hosoda
Abstract: In this paper, we describe our recent work on metal matrix composites (MMCs) with submicron-size TiB2 and Al2O3 particulates that are synthesized in situ from Al-rich Al-Ti-B and Al-TiO2- B powder reactants by reactive sintering. Reaction sequences examined in the two different reactant systems are summarized, and some experimental results on elevated-temperature properties, i.e. thermal expansion, temperature dependence of dynamic tensile modulus and creep behavior, are shown and discussed from micromechanics-based viewpoints.
925
Authors: Shojiro Ochiai, T. Tomida, Toyomitsu Nakamura, S. Iwamoto, Hiroshi Okuda, Masashi Tanaka, M. Hojo
Abstract: The compressive fracture and spalling of multiply-cracked brittle coating layer on metal substrate under tensile stress was studied for the anodic-oxidized aluminum wire with the Al2O3 coating layer and galvannealed IF steel plate with the intermetallic compound coating layer consisting of ζ, δ1 and Γ1 and Γ phases. The thin Al2O3 coating layer on Al wire was fractured by buckling in the circumferential direction by the compressive hoop stress, but thick layer was debonded by the tensile radial stress at interface. The thickness of the coating layer at the transition from the compressive fracture to interfacial debonding was around 30 µm. In the galvannealed steel plate sample, the (ζ+δ1) phases were fractured by buckling in the width direction, resulting spalling of the (ζ+δ1) phases in the first stage, and the remained (δ1+Γ1+ Γ) phases or (Γ1+Γ) phase was again fractured by buckling, followed by the spalling of the remained phase.
929
Authors: D. Doko, N. Miyazaki, Shojiro Ochiai, Hiroshi Okuda, Sang Soo Oh, Masashi Tanaka, M. Hojo, Kozo Osamura
Abstract: Bending behavior of Bi2223/Ag superconducting composite tapes, and the influence of the bending damages on critical superconducting current Ic and n-value that is a measure for the sharpness of the transition from super- to normal conduction, were studied. Following damages, responsible to the reduction in critical current at high bending strains, were observed. (i) Transverse and (ii) longitudinal crackings of the filaments, (iii) interfacial debonding between filaments and silver, and (iv) buckling in compression side. The damage of the filaments arose first locally, resulting in a reduction of the Ic and n-value in the corresponding local portion. The overall Ic and n-values were determined by such a local portion. With increasing strain, the damage of the other portions arose successively, resulting in loss of superconductivity in all portions.
933
Authors: Hiroshi Okuda, Shojiro Ochiai
Abstract: A Monte Carlo simulation using semi grand canonical ensemble method was applied to examine the condition that precipitation free zone (PFZ) appears in an Al-based composite materials under two step aging. The present simulation uses a fcc lattice with a periodic boundary condition for y and z directions, and a grain boundary existing at the end for x direction. A simple grain boundary segregation case gave a nealy parabolic growth law in PFZ width and the volume fraction of precipitates. Different origin of PFZ, namely, mobility or chemical potential, lead to the opposite effect upon secondary heat treatment.
937
Authors: Cheol Woong Kim, Sam Hong Song, Dong Joon Oh
Abstract: If Fiber Reinforced Metal Laminates (FRMLs) were delaminated, the decrease of stiffness and fiber bridging effect would result in the sudden aggravation of fatigue characteristics. It was reported that the delamination of FRMLs resulted from the crack of Al alloy layers and that it depended on the crack growth. When FRMLs with circular holes was un-cracked but was delaminated, it was impossible to analyze them by conventional fracture parameters expressed as the function of cracks. Therefore, a new analytical model called Pseudo Crack Model (PCM) was suggested to compare the delaminations whether cracks were made or not. The relationship between the crack consumption rate (Ccrack) and the delamination consumption rate (Cdel) was discussed and it was also known that the effect of the Ccrack was larger than that of the Cdel.
941
Authors: Suk Bong Kang, Hyun-Ki Kang, Kwang Jun Euh
Abstract: Tungsten/copper composites were produced using an agglomerated feedstock powder by plasma spray and cold spray. In the case of the plasma spray, the external feedstock injection (EFI) and the internal feedstock injection (IFI) were adopted to compare oxidation, microstructure, porosity, and tungsten recovery in the deposits. The IFI deposit had less oxidation, denser microstructure, and more tungsten retention compared to the EFI. Especially, more tungsten particles were melted from the IFI than from the EFI at input power of 25kW. Thermal expansion coefficient of plasma sprayed composite (72W/28Cu vol.%) was approximately 5.2x10-6/K. In the cold spray, no oxidation and more dense microstructures were observed with porosity of less than 1.0 vol.%. However lots of tungsten was lost due to insufficient plastic deformation.
945

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