ELEVATED-TEMPERATURE DEFORMATION PROPERTIES OF A HFC MODIFIED TI-48AL-2MN-2NB MATRIX PARTICULATE COMPOSITE

Rapid solidification techniques in combination with HIPing have been u sed to produce Ti-48Al-2Mn-2Nb and a Ti-48Al-2Mn-2Nb+15 wt% HfC compos ite. While the composite does contain several second phases within the gamma + alpha2 matrix, none was identified to be HfC. The elevated-te mperature properties were determined by constant velocity compression and constant load tensile testing in air between 1000 and 1173 K. Such testing indicated that the elevated temperature strengths of the HfC- modified aluminide was superior to those of the unreinforced matrix wi th the best 1100 K temperature slow strain rate properties for both ma terials being achieved after high-temperature annealing prior to testi ng. Examination of the microstructures after deformation in combinatio n with the measured stress exponents and activation energies suggest t hat creep resistance of the HfC-modified form is due to solid-solution strengthening from carbon and hafnium rather than the presence of sec ond phases.