Journal of Materials Science

, Volume 13, Issue 8, pp 1700–1708 | Cite as

Precipitation in a nickel-beryllium alloy

  • T. V. Nordstrom
  • C. R. Hills
Papers

Abstract

Precipitation was studied in a nickel 1.89 wt% beryllium alloy over the temperature range 400 to 750° C. Below 650° C, the precipitation sequence is analogous to that in the widely studied Cu-Be system:
$$\alpha (supersaturated solid solution) \to \alpha + GP zones \to \alpha + \gamma '_{NiBe} \to \alpha + \gamma _{NiBe} $$
where the equilibrium γNiBe phase is formed by a discontinuous reaction consuming the intermediate γ∼'NiBe. The morphology of the discontinuous γNiBe was too irregular to assign a habit plane. Numerous orientation relations were observed between the αNi and the discontinuous γNiBe. The kinetics of the reaction were found to follow a linear growth with time. The activation energy of 58±3 kcal mol−1 is less than bulk diffusion of nickel but greater than grain boundary self diffusion. Above 650° C, the discontinuous reaction front is arrested before completion because the equilibrium γNiBe forms by continuous coarsening of the γ′NiBe phase. The continuous γNiBe has a habit plane of {113}α. Three closely related orientations were observed at constant ageing parameters for the equilibrium continuous phase. Each has been separately proposed in the literature as a unique relation for the copper-beryllium system. For nickel-beryllium either all three are uniquely present or the accuracy of selected area diffraction technique is such that the small differences in orientation cannot be distinguished.

Keywords

Nickel Activation Energy Beryllium Continuous Phase Habit Plane 

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Copyright information

© Chapman and Hall Ltd. 1978

Authors and Affiliations

  • T. V. Nordstrom
    • 1
  • C. R. Hills
    • 1
  1. 1.Sandia LaboratoriesAlbuquerqueUSA

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