金属間化合物TiAl鋳造材のクリープ挙動

抄録

Compression creep behavior was investigated on a Ti-53.4 mol%Al intermetallic compound which was prepared by ingot casting. The material was made into a single gamma (TiAl) phase by vacuum annealing, though it still retained a columnar structure whose dimensions were about 100 μm in diameter and about 1 mm long. Constant true stress compression creep tests were performed under 80∼400 MPa at 1000∼1150 K in an argon atmosphere.
Normal creep curves were obtained at the higher stress, but the shape of the creep curves gradually changed into sigmoidal-like one with decreasing stress. Stress- and temperature-dependence of the creep rate was evaluated by comparing the creep rates at a fixed true strain. Both the stress exponent and the apparent activation energy decreased with straining and reached constant values, n\fallingdotseq4.3, Q\fallingdotseq330 kJ/mol at around 0.3∼0.5 strain. Minimum creep rates were close to those reported on equi-axed samples and were characterized by n_m\fallingdotseq5 and Q_m\fallingdotseq380 kJ/mol in the high stress region.