A geometrically generalized model of isothermal peritectic transformation

A geometrically generalized analysis of isothermal peritectic transformatio n based on the linearized concentration gradient approximation has been pre sented. The predictions of the present model, as compared with those by the earlier proposed ones, show a better agreement with the kinetic data from the Cd-Ag system. However, the computed kinetics differ from the observed r ates beyond a certain limit, perhaps due to the variation in the shape and size of beta particles and/or depletion of the liquid phase under the exper imental conditions. For an equivalent size (diameter or thickness) of the b eta particles, the kinetics are progressively faster as the geometry of the particles changes from planar to cylindrical or spherical with the related solute flux assuming a 1-, 2- and 3-dimensional nature, respectively. A de tailed parametric study reveals that the product (alpha) and alpha + beta f ield widths exert appreciable influence on the rate of beta consumption. Fi nally, a dimensionless parameter has been proposed to rationalize the proce ss parameters and predict the lower limit of the time required for completi on of the transformation for hyper-peritectic alloys without resorting to a ny lengthy calculation.