Binary Alloys and Density
Date: Winter 2013-14
Can a 2-metal alloy ever have a density greater than that of its most dense component? .
Yes. Osmium and Iridium are some of the densest metals known to us, but we can make them denser still by forming an alloy of the two. The Osmium-Iridium alloy is the densest material known to us. This can happen in two ways: (1) the formation of the alloy allows the smaller of the two elements to fit into the "gaps" between the larger of the two - Imagine a square formed by four tennis balls, and fitting in a ping-pong ball in the space in the middle of the square; (2) the formation of the alloy fixes "cracks" or "errors" in between crystals. Same idea as (1) but this time the alloy formation allows for much larger crystals with fewer breaks or gaps.
Greg (Roberto Gregorius)
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Update: November 2011