Nanostructure synthesis and amorphization during cold rolling

Many forms of materials processing involve departures from full equilibrium conditions, but during processing the thermodynamic constraints usually apply locally at interfaces as a metastable equilibrium. With deformation-induced alloying the stored energy due to defects, grain refinement and solute supersaturation is a measure of the level of metastability that is crucial to consider in microstructure analysis. Systematic study of the deformation structure patterns that develop during the repeated cold-rolling of initial elemental multilayer arrays offers an effective approach to the examination of the mechanisms involved in deformation alloying, nanostructure synthesis and amorphization. For a given alloy the comparison between structure synthesis by melt processing and deformation processing can also provide useful insight. For some systems such as the bulk amorphous Zr-Al-Cu-Ni both methods yield equivalent amorphous states. In marginal glass-forming alloys such as Al-Sm solid-state and melt processing yield distinctly different amorphous phases. In other systems deformation-induced nanocrystal synthesis can be observed from an amorphous initial structure. These developments represent a major level of microstructure control that impacts the structural performance and stability.