Reaction of magnesium boride particles in mechanically alloyed Ti-4wt%MgB2

A Ti-4wt%MgB2 alloy was produced by mechanical alloying (MA) Ti and MgB2 powders for 48 hours in a Spex 8000 mill. TEM analysis of the alloy showed it to consist of a nanocrystalline (10-20 nm) Ti matrix, which enclosed 20-300 nm MgB2 particles. Following heat treatments at 600 degreesC, plate like structures of a previously unknown compound were observed to have extended into the crystals. Convergent beam electron diffraction (CBED) confirmed the new phase to have the same basic arrangement of atom sites as in the NiAs structure. Parallel electron energy loss spectroscopy (PEELS) and energy dispersive X-ray analysis (EDX) measurements identified the elements Ti, Mg and B within these plates. However, the exact proportions of these elements and their distribution within the unit cell could not be determined. (C) 2001 Kluwer Academic Publishers.