Formation of New Intermetallic Phases in the Ta-Ni-Al System

摘要

The peculiarities of structure and phase formation in the 5 Ta-2 Ni-3 Al intermetallic system are studied in the paper. The TaNiAl, NiAl, Ni_2Al_3, and Ta phases are found in the alloy produced by self-propagating high-temperature synthesis (SHS). A transition layer with the composition of Ta(51)Ni_(20)Al_(29) about 1 -2 μm thick is formed on the interface between the unreacted Ta particles and the TaNiAl phase. Remelting of the synthesized alloy at a temperature of about 3000°C leads to the formation of three structural components with the following compositions: Ta_(86)Ni_7Al_8, Ta_(52)Ni_(20)Al_(28), and Ta_(53)Ni_(25)Al_(22). X-ray analysis of the remelted alloy shows the presence of reflections that do not correspond to any of the known phases in the Ta-Ni-Al system. An alloy with a similar composition is synthesized by electrothermal explosion (ETE) under load. The synthesized alloy has a heterogeneous structure and multiphase composition of the surface layer which is similar to the alloy produced by SHS. The central region of the sample produced by ETE is similar to the structural and phase composition of the sample melted at temperature of 3000°C. The obtained data show the possibility of synthesizing in the Ta-Ni-Al system various phases with high Ta content (more than 50 at %).