抄録
Changes in the hardness and structure of dispersion-strengthened Ni-Al2O3 alloys (1∼5 wt% Al2O3) were observed by vacuum annealing at 1200°C for 5 hr. According to the result, the Ni-1%Al2O3 alloy showed the disappearance of the fiber texture and a slight change in hardness by further annealing. Hence the alloy was selected as a material suitable for the study of the steady-state creep mechanism, and creep tests were carried out at 650°∼800°C under a stress of 2∼6 kg/mm2.
The results of the creep tests were compared with those theoretically obtained by assuming the fittest parameter values n and Q in the equation \dotε=Aσnexp(−Q⁄kT), where \dotε is the steady-state creep rate and Q is the activation energy, as proposed by Ansell et al.
The values obtained by the authors are n=4.3–6.5 and Q=34.0–71.7 kcal/mol which are approximate to the theoretical ones on the assumption that dislocation climb is the rate-determining process. Moreover, it has been established that the activation energy for steady-state creep decreases with increasing applied stress.
The values of the shear modulus μ, calculated from the theoretical formula \dotε=(2πλ2)⁄(hμ3kT)σ4D0exp(−Q⁄kT) by use of the experimental values, \dotε and Q, are in the range of 1012 dyne/cm2 which is comparable with those of nickel.
