Daily Science Factlet – Metal Alloys

So while researching for my latest Scrapbook episode for the Naked Scientists, I’ve been learning all about metal alloys. You might think it strange that as a biologist I found this completely fascinating. But I did. And through the generosity of my heart, I’m going to share this cool little factlet (or two, really) about alloys…

Usually when you let an alloy solidify, you want to do it quickly so it forms as many tiny alloy crystals as possible. This is because the joins between the crystals, called grain boundaries, act like walls that stop any faults in the crystals (known as dislocations) from spreading through the alloy and causing it to deform.

BUT, when making turbine blades to go inside jet engines, you want to cool the alloy so it forms one single giant crystal. Grain boundaries are great for stopping dislocations in their tracks, but they also act like little shortcuts for any atoms trying to move around inside the alloy. When the turbine is spinning, some of the atoms in the blades start creeping out towards the edge, as a result of the centrifugal force being caused by the turbine spinning. And if there are grain boundaries for them to take shortcuts along, that’s bad news for the very precisely shaped and sized turbine blade. So, having one single crystal means no grain boundaries, no shortcuts, and less deformation.

Stay tuned for the link to the finished alloys podcast when it’s done!


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