Dispersion Strengthening.

The purpose of this program was to develop a fundamental understanding of the role of finely dispersed second phase particles upon the properties of crystalline solids. Considering that the addition of a dispersed second phase is a common strengthening method, it is surprising to note the lack of information concerning the role of the dispersed second phase on physical and mechanical properties in two phase structures, e.g., heterogeneous nucleation kinetics and phase transformations. The goal of this research program was to enhance the application and development of high strength engineering alloys through achieving a better understanding of the role of dispersed second phases. The scope of this work has been directed towards studying the strengthening behavior of nickel-base superalloys, the strengthening behavior of ferrous martensite, and the kinetics of the austenite to martensite transformation. These studies have focused on the fundamental aspects of these two-phase systems that appear to control the structural characteristics and the mechanical response of these important classes of engineering materials. The following sections will describe the significant results determined during this research grant.