Modelling of high-temperature mechanical behaviour of a single crystal superalloy

A model describing the anisotropic creep deformation of single crystal superalloys has been developed and evaluated using both a database of creep tests and validatory experiments on the alloy SRR99. A previous treatment by Ghosh et al. (1990) that considers deformation to occur by viscous shear on two families of slip systems, octahedral {111}[1 (1) over bar 0] and cube {001}[110], has been extended to allow the description of both primary and tertiary creep, and to simulated deformation under arbitrary loading conditions. A procedure is described for the analysis of the creep data to give the optimum values of the model parameters and the effectiveness of the model in both representing the database and in predicting the deformation characteristics for both complex orientations and complex loading conditions is assessed. In addition to comparison of the model predictions With measured deformation behaviour, the implications of the model for changes in the specimen shape and changes in crystal orientation resulting from asymmetric deformation are considered and compared with experimental measurements.