| 研究概要 |
The project aims in the synthesis of novel light-weight metal matrix nanocomposites (MMnC) with enhanced mechanical properties. In the first year of the project a variety of composite materials were successfully synthesized using commercial grade light alloys as the matrix phase and metallic glass reinforcing phase (nanowires and micron-scale particles). The novel light weight nano-composites exhibit significantly improved mechanical strength, up to three times higher than that of the crystalline matrix. In addition, the composites can preserve good plastic strain before fracture of about 5-10%. On the other hand, it was found that composites in which the metallic glass reinforcing phase crystallizes during sintering may exhibit brittle behavior and fail prematurely at low stress levels. The proper selection of matrix and reinforcing materials porosity and the appropriate processing conditions can eliminate porosity. The amorphous phase plays a significant role in increasing the mechanical strength whereas the softer crystalline matrix phase offers deformability to the composites. New criteria for the selection of proper combinations of matrix and reinforcing phases have been established relating the properties of the starting materials with the synthesis process (sintering) as follows:Tg (reinf) ≦ 0.8 * Tm (matrix) ＜Tsint < Tx (reinf) where Tg(reinf) and Tx(reinf) is the glass transition and crystallization temperature of the metallic glass respectively, Tm (matrix) is the melting temperature of the matrix alloy and Tsint is the sintering temperature.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
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理由
A sophisticated selection of low density crystalline alloys appropriate to be used as matrix materials and amorphous alloys appropriate to be used as reinforcing phase has been made based on the properties and sintering ability of each alloy. Synthesis processes have been analytically investigated; the main synthesis route consists of mixing powders of the crystalline matrix phase with metallic glass nanowires using ball milling and sintering the composite mixture by hot compaction using an induction hot press. A good control of the sintering process (temperature and time) was found to be of critical significance for the porosity and mechanical behavior of the nanocomposites. The sintering temperature Tsint should be between the glass transition Tg and the crystallization temperature Tx, where the metallic glass exhibits a near Newtonian liquid like behavior and close (but lower) to the melting temperature Tm of the matrix alloy where it exhibits thermal softening which can be advantageous for eliminating porosity. The structure and thermal stability of the synthesized nano-composites was characterized by means of electron microscopy, X-ray diffraction and calorimetry. Microhardnes and compression tests were employed to investigate the mechanical properties of the composites. The structure-mechanical properties relations were evaluated in respect to the reinforcement phase dispersion in the matrix. The work done during the first year of the project has been discussed in four international conferences. In addition, two journal articles are currently under preparation.
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| 今後の研究の推進方策 |
Research activities will concentrate on the detailed characterization of the mechanical properties of the novel nano-composites and on the analysis of the deformation mechanisms. In addition, further efforts will be applied on examining alternative preparation procedures aiming to maximize the synergistic effects of the matrix and reinforcing phases. An infiltration casting technique will be used in order to incorporate an assembly of metallic glass nanowires in the structure of low melting temperatures (Mg or Sn) matrix alloys. Mechanical properties and wear resistance of novel nano-composites will be evaluated by hardness, tension, compression, and wear tests. The specific yield strength will be evaluated and compared to that of commercial alloys. The weight reduction, energy savings and corresponding CO2 emission reductions by possible application of the new nano-composites in transportation industry will be evaluated. Synchrotron X-ray-diffraction and electron microscopy studies will be performed in-situ during mechanical testing in order to analyze the evolution of the structure upon mechanical loading in the vicinity of the micron and nano-scale reinforcing phase. The operation of dislocations will be analyzed with special attention to the interactions between the dislocations in the matrix with the reinforcing phases in order to improve our understanding of the strengthening mechanisms in nano-composites. Deformation models will be developed taking into account the various mechanisms that contribute to the strengthening of nano-composite materials.
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| 次年度の研究費の使用計画 |
A part of the budget previewed for the first year has not been spent and is planned to be used during the second year of the project. The main reason for the not-used part of the 1st year budget was a delay related to the provision of a proper in-situ loading set-up to be attached in an available electron microscope. However the difficulties in finding a proper set-up have now been overcome and the purchase of the proper set-up is previewed. This delay has not significantly affected the research activities since, according to the research plan of the project, the in-situ experiments have been planned for the second year of the project.
The budget sums up to 2,295,000 Yen (1,300,000Yen + 995,090 Yen (requested to be transferred to FY 2014). A part of the budget (~1,000,000Yen) is planned to be used for equipment (e.g. in-situ loading set-up and parts for an infiltration casting device). Another part (~350,000 Yen) of the budget will be dedicated to laboratory consumables such as raw materials, inert gases, casting tubes and polishing goods. A third part of the budget (~700,000 Yen) will be used to cover travel expenses for measurements at the Synchrotron Radiation Facility (ESRF) in Grenoble (France) and for the participation to an International Conference where the results of the project will be presented. In addition, a part of the budget (~250,000 yen) will be used for publication expenses and technical software.
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