Intermixing of a system with positive heat of mixing at high strain rates - art. no. 224205

This paper investigates a mode of mechanically driven alloying of elements that are otherwise immiscible at temperatures well below the equilibrium me lting point. Using molecular dynamics simulations, we have studied the allo ying between Ag and Cu, a positive-heat-of-mixing (+ DeltaH) binary system with little solid solubility near ambient temperature, during high strain r ate deformation at temperatures less than or equal to 600 K. Above a critic al strain rate, both elements undergo mechanical melting into undercooled l iquids, which are miscible at 600 K due to the reduced magnitude of the + D eltaH in the liquid state compared with that in the crystalline state. The nonequilibrium deformation maintains the melt state and assists the intermi xing reaction between elemental Ag and Cu through stress-directed atomic fl ow. Upon unloading, the intermixed amorphous Ag-Cu crystallizes towards a s upersaturated fee solid solution. The scheme described is a process of low- temperature amorphization and intermixing of elements, and as such differs from the well-known liquid quench route that starts from an already-mixed l iquid alloy at high temperatures.