應用於金屬粉末射出成形之粗鐵粉之緻密化研究(1/2)
Date Issued
2003
Date
2003
Author(s)
黃坤祥
DOI
912216E002025
Abstract
The first phase of this two-year project was focused mainly on how to improve the density
of compacts made from carbonyl iron powders. The effects of the a phase stabilizers, Mo, P, Si, and W,
on the sintering behavior were evaluated. The dilatometer curve showed that, with a 0.7w/oP addition,
the sintering proceeded in the a phase. No phase transformation occurred at 912℃ and exaggerated
grain growth was prevented. The final sintered density was improved from 87% for the pure iron to
97%. With a 5w/oMo addition, the a-g phase transformation still occurred due to the incomplete
homogenization. However, after all Mo was dissolved into the matrix, the g phase transformed back to
the a phase and resulted in high sintered density of 96%. When W and Si were added, the improvement
on sintered densities was less effective due to their low diffusion rates into iron and the large particle
size used. With mixed additives of 1.67w/oMo-0.23w/oP-0.67w/oSi, a density of 96% and a hardness
of HRB67 were attained. The criteria for a successful sintering in the a phase are (1) the amount of the
additive that is required to keep iron in the a-phase should be minimal, (2) the additive should be fine,
(3) master alloy powders are preferred over the elemental powders, and (4) the heating rate should be
low. This method of adding a phase stabilizers was applied to mixed powder with 60% coarse and 40%
fine powders recently and was found very successful in the cases that have been evaluated. Density of
96.3% and hardness of RB66.2 were obtained on Fe-0.35%P-2.5%Mo alloys.
Subjects
DENSIFICATION
SINTERING
PHASE TRANSFORMATION
PIM
Publisher
臺北市：國立臺灣大學材料科學與工程學研究所
Type
report
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