Spontaneous Pattern Formation in Metallic and Ceramic Materials

This contribution focuses upon the predictable aspects of metallurgical microstructures which by inverse logic have a bearing on similar forms from the mainly ceramic geocosmological record. Among the common forms are needles, plates, cells, and dendrites, together with lamellar, wavy, multidisperse and filamentary arrays. Apart from the usual disparity of time and spatial scales, the main distinctions arise from the stronger directionality of bonds in the case of ceramics, with concomitant stronger anisotropy of surface tension and an attendant facetting propensity. In common are the facts that both liquid-solid and solid-solid transformations with control by diffusion or by chemical reaction or both may be involved. The inversion of the logic comes from the fact that metallurgists try to predict micrographic scale from given thermal conditions, whereas geologists would like, among other things, to estimate historical thermal conditions from observed patterning scales.