News dalla rete ITA

21 Gennaio 2022

Stati Uniti


Florida Tech professor emeritus Martin Glicksman's latest metals/materials science research has implications for the metal casting industry, but it also has a profound personal connection inspired by two late colleagues. Glicksman's research, "Surface Laplacian of interfacial thermochemical potential: itsrole in solid-liquid pattern formation," was published in the November edition of Springer Nature's partner journal Microgravity. The findings may lead to a better understanding of the solidification of metal castings, allowing for engineers to potentially make longer-lasting engines and stronger aircraft and advance additive manufacturing. "The casting, welding, and primary metals production are all multi-billion-dollar businesses of great societal importance, when you think about steel, aluminum, copper—all important engineering materials," Glicksman said. "You can appreciate we're talking about materials, for which even small improvements are worth a lot." Much as crystals form when water freezes, similar things occur when a molten metal alloy is solidified to create cast products. Glicksman's research reveals that during solidification of the metal alloy, surface tension between crystal and melt, as well as the curvature variations of crystals during growth, drives heat flow, even on stationary interfaces. This basic discovery is fundamentally different from the commonly used Stefan balances in casting theory, where the heat energy emitted from a growing crystal is proportional to its growth speed. Glicksman noted that crystallite's curvature reflects its chemical potential: a convex curvature slightly lowers the melting point, while a concave curvature slightly raises the melting point. That is well known from thermodynamics. What is new, and now proven, is that gradients of that curvature can induce additional heat flows during solidification that are not considered in conventional casting theories. Moreover, these heat flows are "deterministic" not stochastic, like random noise, and could, in principle, be controlled to advantage during casting processes to modify alloy microstructures and improve properties. "When you have complicated crystalline microstructures freezing, curvature-induced heat flows occur that could be controlled," Glicksman said. "Those heat flows in the case of a real alloy casting could, if controlled by chemical additions or physical effects, such as pressure or strong magnetic fields, improve the microstructure, which ultimately controls the chemical and mechanical properties of cast alloys, welded structures and even 3D-printed materials." (ICE CHICAGO)

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