The interface between γ and γ' in Ni-Al alloys by HREM

Hector A. Calderon, L. Calzado-Lopez, T. Mori

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations

Abstract

Ni Base superalloys owe their excellent mechanical properties to the presence of particles of γ' phase (Ni3Al with an L12 structure) in a γ matrix (Ni-Al solid solution with an fcc structure). Besides Al, other elements are used to impart either a higher strengthening or improved corrosion properties at high temperature. The interface between γ and γ' becomes of absolute importance for the resulting mechanical properties and technological application. Especially by considering the consequences that diffusion driven coarsening brings about to the particle distribution either with or without the influence of an applied stress or strain. In this work the interface between γ and γ' phases is characterized by means of measurements on phase images obtained from high resolution transmission electron microscopy images (HRTEM). Phase images represent the sample structure much more accurately than typical HREM experimental images and allow correction of spherical aberration and other residual aberrations. The investigation is performed by using a binary Ni-Al alloy as well as technical Ni base superalloys (MC2 and MCNG). While a sharp interface is developed during stress free coarsening in Ni-Al alloys, a wider volume needs to be considered when alloying elements are introduced. Measurements of lattice spacings on phase images and chemical composition from energy dispersive spectroscopy are used to show the interface characteristics in the alloys under consideration. The interface in the binary Ni-Al alloy can be described by micromechanics as a typical misfitting inclusion. In the technical alloys, the presence of concentration gradients changes the expected lattice strains in a given volume around the particles.

Original languageEnglish
Title of host publicationSolid-Solid Phase Transformations in Inorganic Materials
PublisherTrans Tech Publications Ltd
Pages254-259
Number of pages6
ISBN (Print)9783037851432
DOIs
StatePublished - 2011

Publication series

NameSolid State Phenomena
Volume172-174
ISSN (Print)1012-0394

Keywords

  • Electron microscopy
  • Interfaces
  • Micromechanics
  • NI-Based superalloys

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