10 at%Tiの添加によって単結晶化したNi<SUB>3</SUB>Siの変形挙動

Abstract

The plastic behavior of Ni3(Si, Ti) single crystals with 10 at%Ti is investigated, and the effects of temperature, strain-rate and crystallographic orientation with respect to stress axis are examined. An appreciable orientation dependence of critical resolved shear stress (CRSS) is found at 77 K, where the CRSS increases as the orientation shifts from ［001］ toward ［\bar111］. The apparent activation energy for the positive temperature dependence of strength, U, is evaluated to be 7.1 to 7.7 kJ/mol which is smaller than Ti free Ni3Si and is in good agreement with that expected from the data in polycrystals. For orientation near ［001］, where the octahedral viscous flow governs the steady-state deformation following characteristic yield drop, the stress exponent is found to be about 7 which is considerably higher than the values of 3.5-5 in other L12 compounds. The decrement in CRSS by the yield drop is unusually small as compared to the other L12 single crystals. The activation energy for the steady-state deformation is evaluated to be comparable to the value for diffusion of Si in Ni3Al. A good oxidation resistance of the alloy is also made clear in the present work.