Lei Zhang oral presentation (FN3-Fri1-2-4)
Quantification of segregation at grain boundary or coating interface with Tof-SIMS
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, 72 Wenhua Road, 110016 Shenyang, China
In grain boundary and interfacial engineering, segregation of specified species at grain boundary or coating interface is crucial to advanced materials for optimized mechanical properties like creep, toughness and adhesion etc. However, those properties enhancement or degradation really depend on the amount of enrichment along the grain boundary or the coating interface. Quantitative measurement of the segregation is crucial to disclose the real situation at the boundary  or the interface. Due to detect limit at ppm level and rather good resolution in lateral and depth, Tof-SIMS can be a unique analytic tool to quantify the segregation with external or internal standard [2, 3].
Small amount of rare earth has been used as additive to improve the properties of steel. The segregations of the rare earth element Ce at iron grain boundary with the concentration from about ~10 ppm to ~3% were quantitatively investigated with Tof-SIMS. The results revealed a linear correlation of the Ce+ intensity with the change of the Ce concentrations. The ion images showed entire solution and boundary segregation of Ce varied with its amount in iron. The solubility in the grain and the segregation at the grain boundary of Ce were separately quantified based on the external standard of ICP-MS results. Cr2AlC ceramic was applied as a protective coating for Zr alloy from speed-up oxidation at high temperature environment. 3D views and depth profiles revealed the distribution of Cr and Al both in the coating and along the interface. Ratio quantification of CsCr+ and CsAl+ in the coating was consistent with the stoichiometric ratio of Cr and Al in the compound. The quantitative analysis with the internal standard also revealed enrichment of Cr and depletion of Al both on the surface and at the coating/substrate interface. It was implied that Cr was preferentially oxidized on the surface and segregated at the coating/substrate interface.