The nickel-based super heat resisting alloys including Inconel 718 are used for the part of aircraft engine and gas turbine due to their corrosion resistance and the excellent mechanical properties at high temperature. However, these materials are well-known difficult-to-cut materials. Because the usage of the heat-resistant alloy increases in aircraft industry and energy industry, effective cutting technologies are demanded. We propose innovative machining technologies for these metals by using small size ball-nosed end mills under condition of high speed rotating and high speed feed rate. In this paper, we wish to report on the results of high speed milling for nickel-based super heat resisting alloys.

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Friction stir welding (FSW) is a relatively new solid-state joining process primarily for aluminum alloys. FSW has been generating interest because of its association with friction stir processing (FSP), a new technique that essentially employs FSW tooling. FSP is being explored as a thermo-mechanical processing technique to transform a heterogeneous microstructure into a more homogenous microstructure. However, very little information is available regarding FSP characteristics of superplastic alloys. In this study we discuss the trials of Friction Stir Processing (FSP) on Zn-22Al superplastic alloy. Specially, the effects of FSP parameters on strength anisotropy and in-plain anisotropy have been researched. The results were discussed in terms of residual microstructure, mechanical properties and the superplastic properties.

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Porous aluminum is a multifunctional material with lightweight and high energy absorption properties. In this study, A1050-A6061 functionally graded porous aluminum was fabricated by friction stir processing (FSP) route. It is expected that both mixing a blowing agent into aluminum and bonding A 1050 precursor to A6061 precursor can be conducted by FSP. It was shown that A1050-A6061 seamless functionally graded porous aluminum can be successfully fabricated at a holding temperature of 1003 K and at a holding time of 10 min.

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Porous aluminum is a multifunctional material with lightweight and high energy absorption properties. In this study, near-net-shape porous aluminum using die was fabricated by friction stir processing (FSP) route precursor method. Rectangular near-net-shape porous aluminum with a porosity of approximately 70%, which was light enough to float on water, was successfully fabricated at a holding temperature of 1003K and at a holding time of 15 min.

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By sintering the mixture of Cf with high thermal conductivity and Cu powders by SPS process at 1073-1173K in temperature, the preform for low-pressure infiltration of molten aluminum was obtained. Cu particles connected with Cf in preform, and many fine Cu droplets were deposited at Cf surface. Preform has good compressive strength with over 1 MPa, which is enough strength for the low-pressure infiltration. Then, molten pure aluminum was infiltrated to the preform by low-pressure infiltration with 0.2-0.8MPa. As increasing the applied pressure, the density of composites and the dispersity of Cf in composites increased.

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The microstructural features and mechanical properties of type 304 stainless steel castings were correlated with nitrogen contents together with the varying contents of nickel and other composition. Delta-ferrite contents varied with the composition, however, showing relatively lower contents than those predicted by Delong plot. Regression equations were developed among various properties. Tensile strength and abrasive wear were also linearly related to the hardness. Electrochemical measurements showed that the varying chemical compositions and delta-ferrite contents have only a minor effect on the corrosion resistance. Multiple regression analysis was made to explain the contribution of nitrogen and delta-ferrite, which satisfactorily predicted the yield strength, tensile strength, impact energy and abrasive wear. It was shown that the nitrogen caused well-known strengthening effect, and also delta-ferrite was powerful strengthening element.

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Ba added Pb-Ca-Sn alloy has been applied as positive electrode grid material for automotive batteries due to its excellent mechanical properties, high corrosion resistance, good creep properties and recyclability. In our previous studies, it was clarified that Ba added Pb-Ca-Sn alloy had excellent mechanical properties by two-step aging treatment. However, age hardening behavior by the two-step aging treatment hasn't been revealed sufficiently. In addition, effect of two-step aging treatment on microstructure of this alloy has not been understood. In this present, therefore, we investigated changes of the age hardening behavior and the microstructure by two-step aging treatment. Samples were produced by solution treatment of as-cast Ba added Pb-Ca-Sn alloys. The solution-treated alloys were subjected to the two-step aging treatment, and age hardening curves were obtained from micro-Vickers tests. The microstructures were examined by transmission electron microscopy (TEM). From obtained age hardening curves, the maximum hardness increased with holding time in natural aging treatment. TEM observations confirmed that precipitates created by aging treatment were uniformly dispersed throughout crystal grain.

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Effect of particle size distribution on the density and shrinkage of atomized ferrous alloy powder compacts were investigated by controlling particle size distribution of the two bimodal ferrous alloy powders (-25μm / 125-150μm, 25-46μm / 125-150μm). These powders were sintered at 1473K in vacuum after compacted at the pressure of 490MPa. As a result, the sintered compact of -5μm / 125-150μm bimodal powder with fine powder content of 35 mass% showed higher density and lower shrinkage ratio than those of other powder compacts. The improvement of particle packing depends strongly on the size ratio, mixing compositions of the fine to coarse powder. The density increase by the fine powder addition is considered to improve the mechanical properties of the sintered compacts without further addition of alloying elements.

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Effect of Mn content on the microstructure and mechanical properties of TiC/TiB_2 base cermets were investigated by using model cermets with the compositions of TiC/TiB_2-15vol%(Ni + Mn). TiC/TiB_2 ratio is set to molar ratio 57/43 that is quasi-eutectic composition. Mn addition has the possibilities to improve the wettability of the liquid phase. The powder mixtures prepared from TiC, TiB_2, pure Mn, and carbonyl Ni were boll-milled in acetone. After drying, the milled powder were pressed to green compacts and sintered in argon atmosphere for 3.6 ksec. As a result, sintered density and transverse rupture strength (TRS) decreased with increasing Mn content. The decrease of sintered density and TRS was caused by residual pores. Therefore there needs to tailor sintering condition that the elimination of residual pores.

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Ni-6mass%B-55.9mass%Mo-Xmass%Mn model cermets with four levels on Mn content from 10 to 25mass% were prepared to investigate the effects of Mn on the structure and properties of Mo_2NiB_2-Ni cermets. The powder mixtures prepared from pure Mo, pure Mn, carbonyl Ni and MoB were boll-milled in acetone. After drying, the milled powder were pressed to green compacts and sintered in vacuum for 1.2ksec at 1573 and 1598K. The cermet additions of 15mass%Mn exhibits a tetragonal Mo_2NiB_2 (M_3B_2) complex boride. Mn as well as Cr and V changed a crystal structure of the Mo_2NiB_2 complex boride from orthorhombic to tetragonal at 15 mass% Mn addition. However, transverse rupture strength (TRS) and hardness decreased with increasing Mn containing. The decrease of TRS and hardness was caused by residual pores and Mn oxides. Therefore there needs to be a tailoring a sintering condition so that the cermets eliminate those defects.

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The static fracture toughness of Kenaf-Fiber-Reinforced PLA(Poly Lactic Acid) was evaluated using both actual measurement and finite element analysis. The fracture toughness of 20wt% kenaf/PLA composites was found to be about 2 times of neat PLA's value. From the FE numerical analysis results, relief of the stress concentration in the crack tip was observed, which would contribute to the fracture toughness improvement. Furthermore, from the strain energy accumulative rate, introducing kenaf fibers into PLA would reduce the total amount of strain energy in PLA, which would also contribute to the toughness improvement.

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The viscous characteristics of bamboo is experimentally studied. Attenuation of the free oscillation is measured in inverted torsion pendulum method. The damping of bamboo is compared with that of steel.

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Bioactive ceramics attracts attentions as materials of the bone implant, because their high biocompatibility. For example, hydroxyapatite (HA) has bone-bonding ability, and β-ricalcium phosphate (β-TCP) has a high bioresorbability. In this study, HA/P-TCP composites with different content of β-TCP (5,10,20wt%) were prepared by wet mixing of HA and β-TCP powder, compaction of the powders and sintering. Bending strength of HA/β-TCP composites were measured before and after soaking in the simulated body fluid (SBF) up to 4weeks. The bioactivity of HA/β-TCP composites was also evaluated by soaking in SBF up to 4weeks. It was found that the relative density decreased as content percentage of β-TCP increased. It was also found that the bending strength decreased rapidly after 1 week soaking, whereas it doesn't decrease from 2weeks to 4weeks soaking. This result suggested that the apatite layer formed on the surface in SBF reinforced the specimen in spite of the dissolution of the surface constituents.

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The compressive and tensile properties of poly(L-lactic acid) (PLLA) were measured using a universal testing machine and the influence of strain rate on the compressive properties of PLLA were examined using a split Hopkinson pressure bar method. We determined constants of Drucker-Prager yield criterion for PLLA, and drew the yield curves in the plane stress space and in the second deviatoric stress invariant-first invariant of stress. The compressive yield stress of PLLA increased with an increase in the strain rate, but PLLA caused the brittle fracture in the dynamic compressive examination.

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Shot peening is a surface treatment that improves the performance of engineering components. In conventional shot peening, the medium consists of small spheres, which are usually made of high-carbon cast steel; the diameter of the spheres is in the range from 0.3 to 1.2mm. More recently, however, a new type of microshot has been developed to enhance the peening effect. The diameter of the spheres in the new medium is in the range from 0.03 to 0.15mm. In the present study, the effect of microshot peening on the surface characteristics and fatigue strength of spring steel was investigated. The injection method of the microshot was of the compressed air type. The microshots of 0.1mm diameter were high-carbon cast steel and cemented carbide, and the workpiece used was the commercially spring steel JIS-SUP10. The surface roughness, hardness, compressive residual stress, and fatigue strength of the peened workpieces were measured. The surface layer of the workpieces was sufficiently deformed by microshot peening. A high hardness or residual stress was observed near the surface. The shot peening process improved the fatigue life in the high cycle range. The use of hard microshots such as cemented carbide was found to cause a significantly enhanced peening effect for spring steel.

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