Local Modification of P/M Parts to Fully Densify and Enhance Properties

P/M part design is similar to casting in that different properties can be achieved at different locations on a part. Most of this is accomplished through secondary processes, such as repressing or infiltration. While partially successful in modifying properties, it is difficult to alter the local microstructure beyond modifying the pores. A near net-shape thermomechanical process, Friction Stir Processing has been applied to press and sintered P/M parts to both eliminate porosity and homogenize and refine the microstructure. Exceptional improvements in local properties can be made, including increasing hardness, ductility, etc., while decreasing permeability and increasing the response to heat treatment. The action of the friction stir processing is to stir the solid material like cookie dough. There is a local short temperature rise to the hot working range followed by a rapid self quench. Examples of several different materials will be described along with property improvements