A NEW PHASE IN A RAPIDLY SOLIDIFIED AND CONSOLIDATED NBAL3-1 PCT TIB2 ALLOY

Transmission electron microscopy (TEM) investigation was conducted to characterize the microstructure of a rapidly solidified and consolidated NbAl3-1 pct TiB2 alloy. The study demonstrated that the alloy consisted of a two-phase microstructure with second-phase particles distributed uniformly in a NbAl3 matrix. The dominant particle was identified to be an intermetallic phase having a chemical stoichiometry of Nb3Al2 and a hexagonal crystal structure (a = 0.78 and c = 0.52 nm). The structure was determined to belong to the P63/mcm space group. In addition, dispersion of fine NbB particles was also observed. Although the existing Al-Nb binary phase diagrams do not indicate a phase of the type Nb3Al2, it is suggested that formation of such a phase is likely based on analogy with Al-Zr and Al-Hf systems.