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 po wders 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 20-30 0 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 th e new phase to have the same basic arrangement of atom sites as in the NiAs structure. Parallel electron energy loss spectroscopy (PEELS) and energy d ispersive 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) 2 001 Kluwer Academic Publishers.