OPTIMIZATION OF MICROSTRUCTURE DEVELOPMENT DURING HOT-WORKING USING CONTROL-THEORY

A new approach for controlling microstructure development during hot w orking processes is proposed. This approach is based on optimal contro l theory and involves state-space type models for describing the mater ial behavior and the mechanics of the process. The effect of process c ontrol parameters such as strain, strain rate, and temperature on impo rtant microstructural features can be systematically formulated and th en solved as an optimal control problem. This method has been applied to the optimization:of grain size and process parameters such as die g eometry and ram velocity during the extrusion of plain carbon steel. E xperimental results of this investigation show good agreement with tho se predicted in the design stage.