鉄系焼結体における靱性と寸法変化の異方性

概要

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Cylindrical compacts, 40 mm in diameter by 40 mm high, were made from three different iron powders by die-wall lubricating alone or admixing 0. 1-1.5 wt% of zinc-stearate at 196588 MPa, de-waxed at 600-Cfor 30 min, and sintered at 8001200-C for 5-600 min in dissociated ammonia. Small-sized Charpy specimens were cut out from the compacts in the pressing (or axial) direction and in the radial direction.<BR>The anisotropy of the impact value-the ratio of the axial value VA to the radial one VR-was most remarkable in the sintered compacts of the electrolytic powder, which showed the largest weight loss of green compacts in the rattler-test among the three-atomized, electrolytic and reduced-powders used.<BR>The specimens with their length in the pressing direction showed very low impact values over a wide temperature range; the impact value vs. the temperature curve was rather flat. On the fractographs, flat pores perpendicular to the pressing direction, consequently parallel to the fracture surface, were observed.<BR>The anisotropy as well as the dimensional change by axial spring-back during the unloading and ejection after the compaction increased with the amount of zinc-stearate admixed.<BR>In the axial direction, the increases of the impact value and of shrinkage concurred during sintering.
社団法人粉体粉末冶金協会の論文