EFFECTS OF GRAIN-SIZE ON CREEP-BEHAVIOR OF TI-50MOL-PERCENT AL INTERMETALLIC COMPOUND AT 1100-K

Single-phase stoichiometric compounds of TiAl with three different grain sizes of 32, 90 and 170 μm were prepared and the effect of grain size upon creep behaviour was investigated in constant-true-stress compressive creep experiments. All the tests were performed at 1100 K in an argon atmosphere under compressive stresses ranging from 126 to 398 MPa. The creep curves consists of four stages: an instantaneous plastic strain stage, a primary transient stage of the normal type, a stage yielding the minimum creep rate and an increasing creep rate stage. This main feature of the creep curves is not affected by the testing stress and grain size, but the minimum creep rate and its stress dependence are strongly affected by grain size. The minimum creep rate decreased with increasing grain size, and the grain size dependence of minimum creep rate becomes greater with decreasing stress. © 1990.