In the present study / the effects of the powder metallurgical parameters such
as the mixing method, compaction pressure, initial tungsten (W) particle size,
composition, sintering temperature and sintering time on the sintering behavior of
selected high density W-Ni-Cu alloys were investigated. The alloys were produced
through conventional powder metallurgy route of mixing, cold compaction and
sintering. The total solute (Ni-Cu) content in the produced alloys was kept constant
at 10 wt%, while the copper concentration of the solutes was varied from 2.5 wt% to
10 wt%. Mainly liquid phase sintering method was applied in the production of the
alloys. The results of the study were based on the density measurements,
microstructural characterizations including optical and scanning electron microscopy
and mechanical characterizations including hardness measurements.
The results showed that the nature of the mixing method applied in the
preparation of the powder mixtures has a considerable effect on the final sintered
state of W-Ni-Cu alloys. Within the experimental limits of the study, the compaction
v
pressure and initial W particle size did not seem to affect the densification behavior.
It was found that the sintering behavior of W-Ni-Cu alloys investigated in this study
was essentially dominated by the Ni content in the alloy and the sintering
temperature. A high degree of densification was observed in these alloys with an
increase in the Ni content and sintering temperature which was suggested to be due
to an increase in the solubility and diffusivity of W in the binder matrix phase with
an increase in these parameters, leading to an increase in the overall sintering
kinetics.
Based on the results obtained in the present study, a model explaining the
kinetics of the diffusional processes governing the densification and coarsening
behavior of W-Ni-Cu alloys was proposed.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/2/12607576/index.pdf |
| Date | 01 September 2006 |
| Creators | Caliskan, Necmettin Kaan |
| Contributors | Bor, Sakir |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for METU campus |
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