Atom probe field ion microscopy investigations on the intermetallic Ni49.5Al49.5Re1 alloy

Abstract

AbstractThe hypoeutectic intermetallic alloy Ni49.5Al49.5Re1 exhibits promising mechanical properties for high‐temperature applications up to 1250°C, therefore atom probe field ion microscopy (APFIM) investigations were performed in the as‐cast state and after various heat treatments (at 1000°C for different times up to 1000 h and at 1300°C for 1000 h). The imaging properties and the effect of various heat treatments on the solubility and precipitation of Re within the NiAl matrix have been investigated. The field ion micrographs of Ni49.5Al49.5Re1 alloy reveal characteristic imaging features of the NiAl–Re system. Single Re atoms dissolved in the NiAl solid solution matrix were observed as bright imaging species. This is due to preferential retention of Re atoms, as well as the high ionization rate caused by adsorption of Ne image gas atoms by Re atoms. The adsorption of Ne image gas atoms is proved by the occurrence of ReNe3+ and ReNe2+ ions detected in the atom probe mass spectra. Rhenium precipitates of different shapes and several tens of nanometres in size were imaged, as well as small clusters of a few atoms. Conglomerations of a few Re atoms have been detected and the site occupancy of Re atoms in the NiAl superlattice was determined by means of APFIM measurements. Copyright © 2004 John Wiley & Sons, Ltd.