An Al–10%Mg alloy was cold-rolled and aged in order to investigate the effects of cold working on the precipitation behavior and tensile properties. The specimens with various total reductions in area were isothermally aged at 413 K for up to 4.8 × 106 s. The precipitates were examined using optical microscopy, X-ray diffraction and differential scanning calorimetry. The precipitation was promoted by cold rolling and it was confirmed that the preferential precipitation of the stable precipitate, β-phase, at the shear bands was the reason for the stimulated precipitation. Full width of half maximum (FWHM) intensity of an X-ray diffraction peak, 0.2% proof stress and tensile strength showed peak values for the aging time of 1.8 × 106 s. Changes in 0.2% proof stress and tensile strength with aging time were affected by the precipitation and growth of a metastable precipitate, β'-phase, and the decrease in the concentration of solute Magnesium in the matrix.
Effects of Fe and Si as impurities on tensile elongation were investigated in Al–5.5%Mg alloys used for automobile body-panel sheets. Constituent particles content of AlnFe and Mg2Si is increased by the increase of Fe and Si content respectively. Effect of Fe content on elongation strongly depends on the direction of tensile testing. Elongation decreases in longitudinal and 45° directions, but increases in transverse direction with Fe content. This is due to texture change to more random orientation. Average elongation over three directions, (ElL+2ElD + ElC)/4, is decreased slightly with Fe content, which is regarded as due to the grain refinement by AlnFe pinning. On the other hand, elongation is decreased in all directions with increase in Si content, and the decrease in average elongation is much larger than the case of Fe addition. Acceleration in void formation around Mg2Si particles during the last stage of tensile testing is responsible for the higher deteriorating effect of Si.
To clarify the tool wear mechanism in cutting fiber reinforced metal (FRM), turning three kinds of FRM were carried out. They are two kinds of SiC whisker reinforced Al (A6061) and Al2O3 short fiber reinforced Al (A6061). In cutting them, it is known that severe tool wear is observed. So, the tool wear mechanism in cutting them was investigated. Tool materials were five kinds of cemented carbides, two kinds of ceramics and the sintered diamond. In comparison in the cemented carbides, there is the difference of the tool wear by the Co content, the hard grain of the tool and the grain holding strength of the binder. And there is the difference of the wear mechanism in comparison in the three work materials. In cutting SiC whisker reinforced Al (A6061) with the cemented carbide, the tool wear seems to progress due to both of the simple abrasive wear and the falling off of the hard grains. This falling off is produced so that the binder is cut away by the very thin whisker. On the other hand, that in cutting Al2O3 short fiber reinforced Al (A6061) seems to progress due to only the simple abrasive wear. In cutting with two ceramic tools, the severe tool wear is observed in spite of the high hardness. In the diamond tool, the tool wear is very small and this is the most suitable tool in cutting FRM.
Although the possibility of orbital rotary forming of tube-end has been reported for an outward-flange having large value of flaring ratio, the possibility has not been illuminated previously for an inward-flange having large value of nosing ratio. In order to clarify the possibility of the inward-flanging, an orbital rotary forming process in which an inward-flanged shell is formed from a tube by means of rotary conical nosing and subsequent orbital rotary flanging has been proposed. Hard aluminum tubes are formed to inward-flanged shells, and the deformation behavior is examined. It is found that the inward-flange having large value of nosing ratio can be formed from a tube by means of the proposed process. The proposed method with a retainer ring which prevents buckling is found to be effective in improving the nosing limit. The inward-flanging limit of the proposed method is superior to those of conventional inward-flanging methods, such as spinning and press forming. Furthermore, the proposed method with a retainer ring seems to have a significant effect in making the flange thickness more uniform.
The quantitative evaluation of the surface fatigue crack size initiated from an artificial surface defect has been attempted using a DC potential drop (DCPD) technique for an aluminum alloy. A 5052–H34 aluminum alloy sheet with a small blind hole as a surface artificial defect has been used. Potential drop defined as a function of crack area and the correction factor α obtained from experimental data have been used in order to estimate crack depths. The estimated crack depth was slightly smaller than the actual crack depth. The measurement accuracy will be improved by increasing the sensitivity of potential measurement. The surface crack initiated from the artificial surface defect propagated with an almost constant aspect ratio a/c (a: crack depth, c : half crack length) after the crack reached the bottom of the artificial defect under the condition employed in this study.