Hiroyuku Takeishi

Anisotropic Sm–Fe–N magnets produced by compression shearing method

Sm–Fe–N bulk magnet was produced by the compression shearing method. X-ray diffraction studies revealed that the magnet retained the original Sm2Fe17N3 phase structure without any appreciable decomposition of the Sm2Fe17N3 phase and that this phase had a pronounced crystallographic alignment. Magnetic measurements confirmed that the Sm–Fe–N magnet was magnetically anisotropic. The bulk anisotropic Sm–Fe–N magnet exhibited a high remanence value of 9.43kG with a high coercivity of 11.0kOe.

Poly(ε-caprolactone) composites reinforced with short abaca fibres

The tensile properties of poly(∊-caprolactone) (PCL) composites reinforced with short abaca fibres (length ca. 5 mm) prepared by melt mixing and subsequent injection molding were investigated and compared with PCL composites reinforced with glass fibres (GF). The influence of fibre content and surface esterification of the natural fibre on the tensile properties was evaluated. The tensile strength and moduli of all the PCL/abaca composites increased with increasing fibre content. All the PCL/abaca composites had a higher tensile strength than the PCL/GF composites when the fibre weight fraction was the same. The tensile strength of the PCL/abaca composites was improved by surface esterification of the abaca with acetic anhydride or butyric anhydride in the presence of pyridine, because of the increase in the interfacial adhesiveness between the matrix polyester and the esterificated fibre, as is obvious from the SEM photographs.

Poly(butylene succinate) composites reinforced with short sisal fibres

Poly(butylene succinate) composites reinforced with short sisal fibre were prepared by melt mixing and subsequent injection moulding. The influence of fibre length, fibre content and the surface treatment of the natural fibres on the mechanical properties of the composites were evaluated. Regarding fibre length, the tensile and flexural properties of the composites had maxima at a fibre length of about 5 mm. The flexural and tensile moduli of the composites increased with increasing fibre content. Although the tensile strength hardly changed, the flexural strength increased up to a fibre content of 10 wt%. The dynamic mechanical analysis of the composites showed that the storage moduli at above ca.-16°C (corresponding to the glass transition temperature of the matrix) increased with increasing fibre content.

Tribological properties of Al–Si–Cu–Mg alloy-based composite-dispersing diamond nanocluster

This paper describes the tribological properties of diamond nanocluster-dispersed Al-Si-Cu-Mg composite with a comparison to those of diamond-like carbon (DLC)-coated Al-Si-Cu-Mg alloy. Al-Si-Cu-Mg composites containing diamond nanoclusters are fabricated in a powder metallurgy process combined with high-energy ball milling and dynamic consolidation. Friction measurements are made at various loads (0.02-0.2 N) and sliding speeds (0.05-5.0 mm/s) to examine the friction coefficient and wear width, compared to those of Al-Si-Cu-Mg alloy and a DLC-coated alloy. The results indicate that the friction coefficient and wear width of the composite have a tendency to reduce with a decrease in the load and sliding speed, and that they show lower values than DLC-coated samples at <0.1 N, and <0.5 mm/s. The topographical and frictional images in the composite are investigated with AFM, and the reduction of friction in the mesoscopic level can be observed in the diamond nanocluster-dispersed composite.

Dynamic powder compaction for parts with high-aspect ratio

Abstract A computer program has been developed to analyse one-dimensional elasto-plastic wave propagation in a powder-filled container. A numerical integration along characteristic curves is introduced in this program. Characteristic curves are derived from an equation of motion, a constitutive equation and a compatibility equation. In the constitutive equation, the effect of strain rate is taken into consideration. Using this computer program, loading conditions to obtain uniform strain distribution are examined, varying parameters such as the duration and peak of impulses. The following results were obtained: (1) the increase in strain near the fixed end of the container caused by the reflection of the plastic wave contributes to the uniform strain distribution; (2) this wave reflection has the same effect as the usage of a floating die; and (3) for the part with a specific aspect ratio, there is an optimum condition of the duration and peak of the impulse.

Effects of temperature rise on dynamic powder compaction

Abstract The effects of temperature rise caused by plastic deformation and friction on one-dimensional dynamic powder compaction are made clear. The numerical integration of the equation of motion shows that temperature rise is influenced by the peak values of the dynamic load and the friction. In the vicinity of both ends of the powder, the temperature rises with increase in the dynamic load. For greater coefficients of friction, the temperature rises remarkably near to the impact end, the maximum temperature rise of 40°C being observed at the impact end for the dynamic load condition of P 0 = 500 MPa, T = 100 μ s, μ = 0.25. The temperature rise reduces the stress and the wave propagation speed, whilst the strain increases slightly.

Analysis of dynamic deformation mechanisms in powder metals

Abstract In this paper, numerical analysis of stress wave propagation in powder by a characteristic method is presented. The results of the dynamic analysis show the distribution of time-dependent parameters; stress, strain, density, particle velocity, and wave propagation speed. The results prove that the powder has different dynamic behavior as compared with ordinary solid materials, because of its peculiar mechanical properties which depend on the density. Owing to the density change, the wave propagation speed of elastic and plastic waves increases with stress increment. Moreover, the following processes are made clear. The loading wave front gets sleeper with its propagation. After the peak of the stress, an unloading wave takes place. Another secondary elastic wave is caused by the unloading wave. These results obtained by the analysis may be effective in the breaking an oxide surface layer covering aluminum powder, and for controlling density distribution under the dynamic powder compaction.

Consolidation of Nd-Fe-B melt-spun ribbon by compression shearing method

Commercially available Nd–Fe–B melt-spun ribbons (MQ powders) were consolidated at temperatures ranging from room temperature to 573K in ambient atmosphere by the compression shearing method. The resultant bulk materials consisted of the Nd2Fe14B phase together with a small amount of the soft magnetic α-iron phase. The bulk material consolidated at room temperature was magnetically isotropic as was the case for the MQ powders. On the other hand, the bulk material consolidated at 573K was found to be magnetically anisotropic and showed a remanence of 9.2kG, higher than that of the MQ powders.

Punchless blanking of an amorphous alloy

Abstract An amorphous foil has been blanked by a new blanking method, in which a plastic material is used instead of a punch. The plastic is compressed dynamically by electromagnetic transient pressure so as to bulge into the die, the amorphous foil between the plastic and the die being blanked by the die edge. Blanking conditions and their optimization are investigated using such plastics as polycarbonate (PC), nylon 11 (NY) and polypropylene (PP). Punchless micro-blanking is attempted also, the blanking of holes of 0.1 mm diameter being achieved. Experimental results show that the method is suitable for small volume production and fine processing.

High-speed blanking of an amorphous alloy

Abstract An amorphous foil of 28 μum in thickness has been blanked at various blanking speeds, ranging from 0.06 m/s to 15 m/s. A mechanical press is used for the range of 0.06–0.22 m/s, and an electromagnetically actuated press for the higher range of up to 15 m/s. The clearance has been changed also, between 1.0 μum and 5.0 μum. The effects of blanking speed clearance and number of blankings on the blanked surface have been investigated. Furthermore, crystallization of the blanked surface has been examined with the use of the electron beam diffraction method. Crystallization has been found to take place mainly at the burnished area, very little being found at the fractured area and the vein-pattern area.