ABTRACT
The present article describes a method for calculating thecoarsening rate of y' in Ni-based superalloys,which has been applied to both binary Ni-A1 alloys and a wide range of multicomponent alloys. A standard coarsening equation is utilized, but innovative methods for calculating the critical input parameters are presented. The article details methods of estimating interfacial energies and the effective diffusion coefficients that are key parameters for the coarsening model.Self-consistent calculations are made via a computer program in which the only input required is the composition of the alloysand the temperature of coarsening. The effects of coherent strain on the coarsening process have also been analyzed and discussed.
I. INTRODUCTION
NICKEL-BASED superalloys are widely used in applicationns requiring strength at high temperature. Most of these alloys are precipitation hardened by a fine dispersion of y' particles that have an ordered fcc structure (L12). These fine particles coarsen into a lower density of larger particles with a smaller total interfacial area during high-temperature heat treatment or usage. Ardell and co-workers have demonstrated that in binary y-y' systems, the growth of the y' precipitates obeys a diffusion-controlled coarsening model where the average particle radius increases linearly with t,as would be expected from simple coarsening theory. A similar t law has also been observed for a wide ranee of complex commercial alloys containing a large volume fraction of the y' phase. However, as concerns the quantitative modeling of coarsening kinetics, most of the existing information relates to the binary Ni-Al system and is not always consistent even in this simple case. For example, different formulas have been used to calculate the coarsening rate and at least one critical input parameter has had to be "back-calculated" by fitting to experimental data. Usually, the interfacial energy between the matrix and precipitate(『) is derived in this way.
沪公网安备 31011702000137号 
营业执照
微信
新浪微博