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Metallurgical and Materials Transactions A

, Volume 40, Issue 9, pp 2124–2136

First Online: 30 July 2009


Powder metallurgy is a useful route to forming particulate composite materials; however, the densification of hard and soft powder mixtures is usually inhibited by the more refractory phase. The Bi-W powder compacts were uniaxially pressed at room temperature and the compaction behavior and mechanical properties were evaluated. Pressing was performed in incremental steps from ~1 to 540 MPa. After each step, the pressure was relieved and the thickness and sound-wave transit time were measured in situ in the die, in order to determine the density and sound-wave velocity in the compact. The data show that the unreinforced Bi powder compacts to ~98 pct density at 540 MPa. The W reinforcement inhibits the densification process, resulting in increased levels of residual porosity. The compaction behavior was evaluated using a modified Heckel equation, while the porosity dependence of the ultrasonically determined elastic modulus was described by a site percolation approach. Postcompaction sound-wave velocity and Vicker’s hardness measurements show <5 pct anisotropy between the axial pressing and radial directions. The mechanical characterization illustrates the competing effects of the W reinforcement and the associated residual porosity.

Manuscript submitted June 15, 2007.

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Autor: L. Peter Martin - Andrea M. Hodge - Geoffrey H. Campbell


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