Abstract
With the aim of preparing high performance oxide-dispersion-strengthened tungsten based alloys by powder metallurgy, the W-Y2O3 composite nanopowder precursor was fabricated by an improved wet chemical method with anion surfactant sodium dodecyl sulfate (SDS) addition. It is found that the employment of SDS can dramatically decrease W grain size (about 40 nm) and improve the size uniformity. What’s more, SDS addition can also remarkably improve the uniform dispersion of Y2O3 particles during the synthesis process. For the alloy whose powder precursor was fabricated by traditional wet chemical method without SDS addition, only a few Y2O3 dispersoids with size of approximate 10–50 nm distribute unevenly within tungsten grains. Nevertheless, for the sintered alloy whose powder precursor was produced by improved wet chemical method, the Y2O3 dispersoids (about 2–10 nm in size) with near spherical shape are dispersed well within tungsten grains. Additionally, compared with the former, the alloy possesses smaller grain size (approximate 700 nm) and higher relative density (99.00%). And a Vickers microhardness value up to 600 Hv was also obtained for this alloy. Based on these results, the employment of SDS in traditional wet chemical method is a feasible way to fabricate high performance yttria-dispersion-strengthened tungsten based alloys.
Highlights
It is well accepted that the brittleness of tungsten-base alloys is extremely sensitive to their microstructure including tungsten grain size, the uniformity of structure, porosity and grain boundary segregation of impurity elements
It can be observed that the full width of half maximum (FWHM) of the peaks corresponding to tungsten become broader and the intensities of these peaks decrease after introducing sodium dodecyl sulfate (SDS) in traditional wet chemical method, which confirms the grain refining effect of SDS addition
For the alloy whose powder precursor was produced by improved wet chemical method, the microstructure characterization shows that the Y2O3 particles are dispersed both within tungsten grains (2–10 nm) and at the tungsten grain boundaries homogeneously
Summary
It is well accepted that the brittleness of tungsten-base alloys is extremely sensitive to their microstructure including tungsten grain size, the uniformity of structure, porosity and grain boundary segregation of impurity elements. A uniform distribution of bonding phase in tungsten matrix can enhance integrated mechanical properties of the materials, is a key parameter for obtaining high-performance tungsten-base alloys[13]. It is essential to prepare tungsten-base alloys with ultrafine grains, uniformly distributed dispersion phase particles and high relative density to enhance the comprehensive mechanical properties of the materials. The oxide particles in powder precursor distribute inhomogeneously and tend to agglomerate at grain boundaries to some extent, greatly weakening the improvement effect of rare earth oxides on the properties of tungsten-base alloys, especially the DBTT and recrystallization temperature. It is found that the high-quality W-Y2O3 composite powder consisted of uniform nano W grains (about 40 nm) and homogeneously dispersed Y2O3 (about 2–10 nm) was successfully synthesized by the improved wet chemical method. The oxide nanoparticles are dispersed within tungsten grains (about 2–10 nm) and at tungsten grain boundaries more uniformly in the former one and its Vickers microhardness is up to 600 Hv
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