Synthesizing monotectic alloys using friction stir processing

Monotectic alloys possess great technological significance. Some of their applications include bearings in car engines, electrical contacts and switches, giant magnetoresistive materials (GMR), and superconductors. At present, these alloys are processed using conventional solidification techniques. However, in the chemical composition range of commercial interest, these alloys consist of a large miscibility gap in liquid state, which makes controlling morphology and distribution of minority liquid phases very difficult. This solidification characteristic eventually leads to undesired microstructural evolution, especially under earth gravity, unless some special care is taken during solidification of such alloy systems. In this context, solid-state processing provides a unique approach to address some of the solidification related issues for monotectic alloys, e.g., earth gravity assisted separation of immiscible liquids. To demonstrate the use of friction stir processing (FSP), a thermo-mechanical processing tool, in fabricating monotectic alloys, we have successfully synthesized an Al-Bi alloy using FSP. In this presentation, we will share results on microstructural evolution and mechanical properties of Al-Bi alloy synthesized using FSP.