GROWTH MORPHOLOGY OF THE NIAL-V IN SITU COMPOSITES

摘要

Intermetallic Matrix Composites (IMC's) are considered candidate materials for high temperature applications provided that the proper combination of properties can be developed. Among a large number of intermetallics, a particular interest has been shown in the NiAl based composites. Attractive properties of this compound include higher melting temperature, better oxidation resistance, and lower density when compared to conventional superalloys. However, insufficient low temperature fracture resistance is a major drawback. Stringent requirements for chemical and mechanical compatibility between the matrix and the reinforcing phase have recently renewed interest in directional solidification of the eutectic alloys. Microcomposite structures generated by directional solidification of eutectics offer many unique microstructural advantages, including thermodynamic stability up to the melting temperature, directional alignment and fine dispersion of component phases. Although a large number of directionally solidified eutectic systems have been investigated so far, little information on the eutectics in NiAl-V system has been reported. The present paper is concerned with the growth morphology of the NiAl-V in situ composites. Samples prepared by arc melting were processed in a directional solidification furnace with induction heating. The main objective was to analyze the solidification microstructure and morphology regarding the growth conditions and composition. Sample characterization, beside the optical and scanning electronic microscopy, included the use of differential thermal analysis (DTA), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) technique.