Abstract
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.
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.
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.
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.
In the axial direction, the increases of the impact value and of shrinkage concurred during sintering.
