The branch's research is directed toward understanding metallic materials by controlling phase transformations, microstructure, and atomic ordering. We study the fundamental mechanisms associated with basic phenomena in metals and alloys. The influence of microstructure and defects - such as vacancies, dislocations, internal interfaces, and impurity atoms - are correlated with mechanical, electrical, and thermal properties.

Microstructure and Phase Transformations. Efforts are aimed at modeling phase-transformation behavior and grain-growth in terms of atomic mechanisms. Experimental characterization includes morphology, crystallography, formation mechanisms, kinetics, and overall microstructural evolution behavior by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Electron Backscatter-Pattern Analysis (EBSP) with Orientation Imaging Microscopy (OIM), Energy Dispersive Spectroscopy (EDS) and optical microscopy. Emphasis is on model ferrous alloys, high-strength low-alloy (HSLA) steels used in Navy applications, rapidly solidified ultrahigh carbon steels, commercial aluminum alloys, magnetic thin films and high-temperature superconductors.

Mechanical Behavior. Theoretical and numerical methods to predict the dynamic response of advanced materials subjected to extreme thermal and mechanical environments are developed and applied.

Fatigue Initiation and Propagation Mechanisms. A novel concept is being exploited to understand the fundamental aspects of fatigue crack propagation in a wide variety of materials (including aluminum, titanium, and steel) in alloys and in ceramics. This concept seeks to unify crack propagation and environmental effects.

Innovative Processing. Techniques to develop new materials and processes, such as nanosized materials and rapidly solidified powders, are studied to improve materials for future use. Current efforts in these areas are in rapid solidification of powders and super-plastic consolidation.

Joining. The thrust of the joining program is to be able to predict properties of a weldment based on the process and the chemistry of the parts being joined. Models of heat flow, including convection and conduction, are used with a thermodynamics-based model for the decomposition of austenite to calculate the volume traction of phases in steels. Mechanical properties are also being measured and calculated. Detailed processing-microstructure-property correlations are experimentally developed and compared to models. An ultrahigh vacuum system with a heating coil and a load frame is being used to examine the fundamentals of solid-state joining.

The Physical Metallurgy Branch consists of three sections

• Deformation and Fracture Section
• Joining and Transformations Section
• Materials Characterization Section