Microstructure of the microalloyed NiAl-V eutectics

This study addresses the need for advanced high-temperature materials in aerospace and energy sectors by investigating the Al-Nb-Nisystem, specifically focusing on the impact of nickel addition on the Al3Nb-Nb2Al eutectic and the discovery of novel ternary eutectic reactions. The research involved preparing Al-Nb eutectic alloys from high-purity elements and systematically examining the microstructural evolution and phase compositions under varying nickel concentrations and solidification growth rates. A novel ternary eutectic reaction, L Nb₂Al+Al₃Nb+AlNbNi, was identified, occurring at a precise composition of Al-40. 4Nb-2. 42Ni and a temperature of 1553. 6^C. The third constituent, an Al-rich AlNbNi phase (Al-33. 3Nb-12. 3Ni), was found to contribute to a regular, predominantly fibrous microstructure despite the intermetallic nature of its phases. While increased growth rates resulted in reducedinterphase spacing and changes in phase volume fractions, further increases led to the degeneration of the eutectic microstructure. The study also discredits the existence of the previously proposed Al5Nb2Ni phase and observed that nickel addition promotes a progressivetransition from lamellar to fibrous morphology.