![Sample our Physical Sciences journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/110819/TOC-Subject-Sample-2021-Physical-Sciences.jpg"})
Abstract
Four carbonyl-nickel powders with bulk densities between 0.6 and 1.0 g/c.c. have been examined and their behaviour on loose sintering in dry hydrogen between 700 and 1000°C assessed. The properties of the porous plates produced were determined from porosity, pore-spectrum, fibre-strength, and electrical-resistivity measurements.
It is shown that the majority of shrinkage occurs in the vertical direction by collapse of the powder bed in the first stage of sintering and that sub-sequent densification in the second stage is considerably slower. The increase in strength and decrease in electrical resistivity is more rapid in the second stage. The strength and resistivity are related to porosity, indicating a slight preference for a low-bulk-density powder when considering porosities in the range between 80 and 90%.
Limited consideration is given to the effects of restraint and of atmospheres other than dry hydrogen, but although these modify the sintering behaviour the relationships with porosity obtained with dry hydrogen appear to hold.
Notes
* Manuscript received 7 June 1963. Contribution to a Symposium on “Residual Porosity in Powder Metallurgy” to be held in London on 21 and 22 October 1963.