Effect of grain size and partial disordering on ductility of Ti3Al in the temperature range of 20-600 degrees C

The effect of grain size and partial disordering on ductility and how stres s of an intermetallic Ti3Al was studied in the temperature range of 20-600 degrees C using tension and compression testing. The ductility of the fully ordered material increased considerably when the grain size decreased from 27 to 0.1 mu m, and, at the smaller grain size, an elongation of 4.8% was achieved at room temperature. Partial disordering of the crystal lattice le d to a decrease in ductility at temperatures below 500 degrees C, but had n o influence on the ductility at 500 or 600 degrees C. The critical grain si ze at which a brittle-to-ductile transition occurred in the fully ordered m aterial was determined for each temperature studied. This critical grain si ze increased as the temperature was increased. It was found that, when the mean grain size decreased and temperature increased, the fracture mode chan ged from a brittle transcrystalline mode to a brittle intercrystalline mode and, finally, to a ductile transgranular mode. The increased ductility was correlated with an enhanced grain boundary relaxation capability at increa sed temperatures and decreased gain sizes. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.