Geoffrey Greenwood is widely known for studies relating atomic mobility, particularly across and along interfaces, to microstructural changes, dimensional instability, and phase separation in materials subjected to stress, high temperatures, irradiation and chemical forces. His work laid the foundation for understanding the growth of precipitates in solids at high temperatures.
He was the first to recognise that, in an assembly of precipitates of different sizes, reduction of surface energy by shrinkage of smaller precipitates and the growth of larger ones would lead to an increase in the cube of their mean diameter linearly with time. This insight has since been highly developed to become one of the central features of modern understanding of the evolution of microstructure in the solid state.
Geoffrey has also played a key role in establishing important features of the combined effects of internal and external stresses, the growth of gas bubbles in irradiated metals and in recognising diffusion creep as a separate mode of deformation in metals and alloys, including its occurrence in some materials used in nuclear reactors.
Emeritus Professor of Metallurgy, Department of Materials Science and Engineering, University of Sheffield