Copper oxide has been detected in the copper containing alloys of Standard Reference Material (SRM) 482. This occurrence is significant because it represents heterogeneity within a standard reference material that was certified to be homogeneous on a micrometer scale. Oxide occurs as elliptically to spherically shaped precipitates whose size differs with alloy composition. The largest precipitates occur in the Au20-Cu80 alloy and range in size from submicrometer up to 2 υm in diameter. Precipitates are observed using light microscopy, electron microscopy and secondary ion mass spectrometry (SIMS). SIMS has demonstrated that the precipitates are present in all wires that contain copper. Only the pure gold wire is precipitate free. Initial results from the analysis of the Au20-Cu80 alloy indicate that the percentage of precipitates is less than 1% by area. Electron probe microanalysis (EPMA) of large (2 υm) precipitates in this same alloy indicates that precipitates are detectable by EPMA and that their composition differs significantly from the certified alloy composition. The small size and low percentage, of these oxide precipitates minimizes the impact they have upon the intended use of this standard for electron probe microanalysis. The heterogeneity caused by oxide precipitates however may preclude the use of this standard for automated EPMA analyses and also for other microanalysis techniques.
Citation: Journal of Research (NIST JRES) -
Volume: 107 No. 6
NIST Pub Series: Journal of Research (NIST JRES)
Pub Type: NIST Pubs
copper-gold alloy, electron probe microanalysis, metallography, oxide inclusions, sample preparation, secondary ion mass spectrometry, Standard Reference Material 482