Atomistic simulation of defect structure in Nb-Ti-Al

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Virginia Polytechnic Institute and State University

Intermetallic compounds are being considered for possible high temperature aerospace applications, yet they are often hampered by a lack of room temperature ductility. However, a B2 phase in the ternary Nb-Ti-Al system has been discovered which exhibits considerable ductility at room temperature. Three different alloy compositions which exhibit this ductile phase were examined by computer simulation using the Embedded Atom Method. The site occupancies of the ternary B2 structure were determined and linked to the defect interaction energies of Ti and Al in Nb. The defect structures examined in each intermetallic included anti-phase boundaries, twins, pseudo-twins, free surfaces and dislocations. An estimation of the ductility of these intermetallics was made using both the Rice and ZCT ductility criteria. Comparison of the criteria with values for other B2 intermetallics leads to the conclusion that the simulated Nb-Ti-Al B2 compounds are ductile.