This investigation incorporates the development and control of microstructure and properties into a computer aided design/computer aided manufacturing (CAD/CAM) environment for materials design. An integrated computer model has been developed which predicts the microstructure and properties based on the material processing and the material composition. The material processing includes the extrusion parameters and the aging conditions employed during heat treatment. The material being utilized as a demonstration medium is a special precipitation hardenable aluminum-lithium-zirconium (Al-Li-Zr) alloy which has been direct-chill (D.C.) cast and direct extruded. A model has been developed based on a series of quantitative transmission electron microscopy (TEM) investigations to predict microstructure from the composition and material processing. This model, referred to as the microstructural model, provides the basis for the overall CAD/CAM model for materials design. Also included is an analysis of the microstructural mechanisms that contribute to the strengthening of precipitation hardened alloys that contain shearable precipitates. A number of existing models regarding particle shearing and looping mechanisms in precipitation hardened systems were evaluated regarding their suitability in describing the Al-Li aging and strengthening behavior. These analytical models are incorporated with the microstructural model to make theoretical predictions for the critical resolved shear strength.

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