ELASTIC EFFECTS ASSOCIATED - WITH THE FORMATION OF PRECIPITATES IN A FREE THIN-LAYER .1. THE ELASTIC FIELDS

The present study is concerned with the relationship between the elast ic strains and stresses that are associated with the presence of dilat ing precipitates in a thin isotropic, homogenous free layer, and the r esulting microstructure. The elastic fields near the free surfaces of the thin layer are calculated using a superposition of two known solut ions in the theory of linear elasticity. The redistribution of the ela stic fields in the layer, with respect to that in an infinite matrix, is interpreted as resulting from the reduced constraints on the displa cements parallel to the free surfaces. The reduced constraints enable the setting up of large lateral tensile strains and stresses between t he precipitate and the free surfaces. The most significant result is t hat the hydrostatic stress component in the vicinity of the precipitat e has the same sign as the transformation strain of the precipitate. I n part II, the elastic interaction energies between precipitates and f ree surfaces will be deduced and their influence on the development of the microstructure will be discussed.