• Journal of Powder Materials
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• v.18 no.5
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• pp.406-410
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• 2011

Green strength is an important property of powders since high green strength guarantees easy and safe handling before sintering. The green strength of a powder compact is related to mainly mechanical and surface characters, governed by interlocking of the particles. In this study, the effect of powder surface roughness on the green strength of iron powders was investigated using a transverse rupture test. Three-dimensional laser profiler was employed for quantitative analyses of the surface roughness. Two different surface conditions, i.e. surface roughness, of powders were compared. The powders having rough surfaces show higher green strength than the round surface powders since higher roughness leads increasing interlocked area between the contacting powders.

• Korean Journal of Materials Research
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• v.3 no.2
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• pp.111-120
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• 1993

Abstract In this study, the Mo-Hf-O ingots containing 0.31-1.14at % Hf and 0.08-1.00at % 0 were prepared by plasma arc melting. The change of microstructure depending on the condition of heat treatmen~ was analysed by optical microscophy, auger electron microscophy, and transmission electron microscophy. Molybdenum powder with the oxygen content of 830ppm was compacted, and then melted. The oxygen content of molybdenum ingots was detected to be 40 -130ppm. As the contents of Hf and 0 increased, the grain size of ingots decreased. When molybdenum igot containing l.14at % Hf and 1.00at % C was heat treated, p-molybdenum carbide in grains was transformed into ${\alpha}$-molybdenum carbide at 130$0^{\circ}C$. Between 140$0^{\circ}C$ and 150$0^{\circ}C$, the precipitation of hafnium carbide was due to the reaction of solute Hf and C, and the hafnium carbide was saturated at grain boundaries at 150$0^{\circ}C$. When the sample was heat treated from 150$0^{\circ}C$ to 170$0^{\circ}C$, Hafnium oxide more stable thermodynamically precipitated both at grain boundaries and in grains after hafnium carbide had been dissolved at grain boundaries.