Aluminum is ubiquitous in our modern age, but it’s surprisingly hard to produce alloys for it without putting up with significant waste from bad mixtures. MIT researchers Antoine Allanore and Samuel R. Wagstaff have been studying how aluminum alloys harden and have come up with a way to use jets to produce more even distributions of copper and manganese in castings.
Direct-chill casting is a semicontinuous way of producing aluminum alloy ingots by quickly cooling the molten metal as it’s poured into chilled molds. It’s a very effective process, but according to Allanore and Wagstaff it leaves something to be desired in terms of quality control.
Though an ingot may look perfectly sound on the outside, it may have patches high or low in copper or manganese ranging in size from inches to feet, resulting in weaker slabs of cast metal. This can mean large amounts of aluminum being relegated to the scrap pile.
The problem is these patches often aren’t visible on the surface of an ingot because they tend to form in the center of the casting. This means they remain hidden until the casting is rolled. This slows down production and hinders the making of large slabs for trucks or airplane wings.
To produce a more uniform casting, the MIT researchers turned to the macrosegregation index, which is a way of measuring how much an actual mixture differs from an ideal chemical makeup. By manipulating this, the alloy mix can be made 20 percent more even.
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