SAXS and XAFS characterization of precipitates in a high-performance Cu-Ni-Si alloy

Yohei Takahashi, Takashi Sanada, Shigeo Sato, Toshihiro Okajima, Kozo Shinoda, Shigeru Suzuki

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

Analyses of small-angle X-ray scattering (SAXS) and X-ray absorption fine structure (XAFS) were performed for characterizing precipitates formed in a Cu-3.1 at %Ni-1.4 at%Si alloy, the strength and electrical conductivity of which were improved by aging. SAXS profiles and XAFS spectra of samples aged at 720 K for different periods of time after a solution treatment were measured. SAXS profiles of samples, which were aged after the solution treatment and subsequently cold rolled, were also measured to investigate the effect of dislocations on precipitation. The results of SAXS measurements showed that nanometer-size precipitates formed in the alloy samples during isothermal aging at 720 K. The precipitates in the samples without cold rolling were coarsened in a single modal size distribution with increasing aging time. In contrast, the precipitates formed in the cold-rolled samples appeared to be coarsened in a multi-modal size distribution with increasing aging time. This aging characteristic of the cold-rolled samples is presumably attributable to their good electrical conductivity. The results of XAFS measurements at the Ni K-edge showed that nickel was substituted for copper in the face-centered cubic (fee) copper matrix and that the local structure around nickel was changed by isothermal aging. With increasing aging time, extended X-ray absorption fine structure (EXAFS) functions at the Ni K-edge of the samples were found to be changed, which implies that nickel atoms were precipitated as nickel-silicon clusters or intermediate compounds in the fee copper matrix. In addition, X-ray absorption near edge structure (XANES) spectra at the Ni K-edge indicated that the electronic structure of nickel in the samples was influenced by silicon during aging.

Original languageEnglish
Pages (from-to)101-104
Number of pages4
JournalMaterials Transactions
Volume48
Issue number2
DOIs
Publication statusPublished - 2007 Feb

Keywords

  • Copper base alloy
  • Precipitation
  • Small angle X-ray scattering
  • X-ray absorption fine structure

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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