EFFECT OF ALUMINUM ON ORDERING OF HIGHLY STABILIZED BETA-TI-V-CR ALLOYS

The microstructure of Ti-(20-37) V-15 Cr-(0-7)Al (wt-%) alloys has bee n examined using optical microscopy, scanning electron microscopy (SEM ), transmission electron microscopy (TEM), and X-ray and neutron diffr actometry: It has been found that addition of 4 wt-%Al to the Ti-V-Cr ternary system leads to the ordering of the bce beta matrix (A2) into a B2 structure. The order/disorder transition temperature (T-c) was de termined by in situ TEM heating of an alloy of Ti-32V-15Cr-5.6Al Co be similar to 620 degrees C. The site occupancy of Al and Cr in the B2 w as determined by atom location by channelling enhanced microanalysis ( ALCHEMI) to be on the V and Ti sites, respectively. The results are di scussed in terms of the effects of Al on ordering in the highly stabil ised beta-Ti-V-Cr-Al alloys.