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Agitating the aluminum pot

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MIT researchers demonstrate that strong churning during hot liquid state can produce stronger, more uniformly structured large aluminum casts. Solidified cross-sections from aluminum ingots were made using a conventional method (top) and a new jet metal process developed by MIT researchers. “The introduction of the jet induced a completely different recirculation of the grains, and therefore you get different microstructure all along the section,” says MIT Assistant Professor Antoine Allanore.
Samuel Wagstaff PhD ’16 stands next to 6,000 aluminum alloy ingots at Novelis in Sierre, Switzerland. Over the past three years, Wagstaff and MIT assistant professor of metallurgy Antoine Allanore developed a new process that uses a turbulent jet to reduce macrosegregation defects in aluminum alloys by 20 percent. The ingots pictured are destined for the Land Rover-Jaguar group.
A scanning electron microscope image shows large-grain structures contrasting with finer-grain structures in a sample taken during a direct-chill aluminum alloy casting. The “floating grains” were solid in slurry, a transition zone between liquid and solid, before it was rapidly cooled for the sample, MIT graduate student Carolyn Joseph says.
MIT graduate student Carolyn M. Joseph is working under MIT Assistant Professor Antoine Allanore to study how grains that cause macrosegregation, or uneven distribution of alloying elements, form in an aluminum alloy casting.Left to right: MIT Assistant Professor Antoine Allanore was joined at a recent TMS Bladesmithing Competition by graduate student Brad Nakanishi and MIT alumnus Samuel Wagstaff PhD ’16. Allanore and Wagstaff developed a new process that uses a turbulent jet to produce stronger, more uniformly structured solid aluminum alloys.


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