The effect of microstructures on creep behavior of Ti-48Al-2W intermetallic compounds

Abstract

The creep behaviors of Ti-48Al-2W intermetallic compounds have been investigated by constant stress tests at the temperature range of 750-850degreesC under the stress range of 170-440 MPa. The effects of lamellar grain size and lamellar volume fraction on the creep behavior of Ti-48Al-2W compounds were analyzed. The minimum creep rate was almost independent on the lamellar grain size in the range of 135-400 mum, while the minimum creep rate was sensitively dependent on the lamellar volume fraction. The minimum creep rate decreased with increasing the lamellar volume fraction in the range of 70-100%. The activation energies were measured as 298 kJ mol(-1) for the near gamma structure, 340 kJ mol(-1) for the near lamellar structure and 345 kJ mol(-1) for the fully lamellar structure. The stress exponents were measured as 6.4 in the near gamma structure, 4.9 in the fully lamellar structure and 5.0-5.5 in the near lamellar structure having the lamellar volume fraction of 70-95%. The dislocation structures in the crept specimen were analyzed. The creep rates of near lamellar structure were analyzed by the rule-of-mixtures from the creep rates of fully lamellar structure and near gamma structure. (C) 2002 Elsevier Science B.V. All rights reserved.