Abstract
Two series of tungsten-rhenium-osmium alloys have been successfully prepared by powder-metallurgy techniques in sintered bar form. The first series, containing nominally 5% Re and up to 2·25% Os, are single-phase alloys consisting of an α solid solution of tungsten, rhenium, and osmium. The second series, containing nominally 26% Re and up to 11·3% Os, consist of the same solid solution up to ∼1·67% Os, the higher osmium contents giving a two-phase alloy consisting of the α solid solution and the hard, brittle a phase. The two-phase alloys are of the age hardenable type and their properties are thus dependent on the thermal history.
The alloys containing ∼26% Re and between ∼0·69% and 4·5% Os are particularly prone to deformation twinning at room temperature, the tendency reaching a maximum at ∼1·67% Os. This observation may be interpreted as an extension of the rhenium alloying effect, the double addition of rhenium and osmium giving an interactive as well as additive effect of Os atoms. Confirmation of the lower energy of the twinning planes is also apparent from the mode of precipitation of the σ phase on preferential planes in this composition range.
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