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Multiphase Nickel Aluminides Produced by Hot Isostatic Pressing of Nanostructured Powders Obtained by Mechanical Alloying

  • : Martin, J M1
  • : 1CEIT & TECNUN
  • : PDF Download
  • : 2012

Abstract

Multiphase ?-NiAl/??-Ni3Al/?-Ni base intermetallics with the composition 44.24Ni-22.13Al-22.13Fe-0.5B-7.5Cr-1.0Ti-2.5Ta (at%) were produced by HIP of nanostructured powders of a metastable Ni base solid solution (NiSS). These powders were obtained by mechanical alloying of elemental powders under argon. DSC runs revealed that the synthesis of the intermetallic phases from the NiSS occurs by solid state diffusion rather than by the conventional combustion synthesis observed in elemental mixes. Moreover, melting takes place in a lower range of temperatures. After vacuum encapsulation in a steel can, the powders were consolidated by HIP at 1000ᄃC for 1 h under 100 MPa and subsequently heat treated to modify the as-HIPed microstructure. The porosity of the final samples was negligible. C, O, N, and S were measured for both powders and final samples. Mechanical properties were evaluated by Vickers hardness and tensile tests (from RT to 1000ᄃC). Microstructural characterization involved XRD and FEG-SEM. The relationship of the mechanical properties with these microstructural features is discussed.
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