An in situ USAXS-SAXS-WAXS study of precipitate size distribution evolution in a model Ni-based alloy

Ross N. Andrews, Joseph Serio, Govindarajan Muralidharan, Jan Ilavsky

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

Intermetallic γ′ precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS-SAXS-WAXS) analysis can be used to evaluate the temporal evolution of an alloy's precipitate size distribution (PSD) and phase structure during in situ heat treatment. Analysis of PSDs from USAXS-SAXS data employs either least-squares fitting of a preordained PSD model or a maximum entropy (MaxEnt) approach, the latter avoiding a priori definition of a functional form of the PSD. However, strong low-q scattering from grain boundaries and/or structure factor effects inhibit MaxEnt analysis of typical alloys. This work describes the extension of Bayesian-MaxEnt analysis methods to data exhibiting structure factor effects and low-q power law slopes and demonstrates their use in an in situ study of precipitate size evolution during heat treatment of a model Ni-Al-Si alloy.Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS-SAXS-WAXS) provides in situ evaluation of the precipitate size distribution (PSD) and phase structure temporal evolution during heat treatment. A method for extraction of an arbitrary PSD in the presence of interparticle interactions is described and illustrated for study of PSD evolution.

Original languageEnglish
Pages (from-to)734-740
Number of pages7
JournalJournal of Applied Crystallography
Volume50
Issue number3
DOIs
StatePublished - Jun 2017

Keywords

  • Bayesian inverse transformation
  • USAXS-SAXS-WAXS
  • precipitation hardening
  • small-angle X-ray scattering
  • ultra-small-angle X-ray scattering
  • wide-angle X-ray scattering

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