From the mushy zone to squishy cells

20140711_104433Today I am at conference on metals crystallisation, next
Friday I will be co-chairing a workshop on structure in living cells. These are two of four back-to-back conferences will be attending over the next two weeks. With this many conferences it is good to have variety. This one is near Egham in Surrey, the picture shows part of the venue.

I am not a metallurgist, so I am learning at this meeting. The first speaker today was very entertaining. He spent 10 minutes slagging off* practices in foundries. His argument was simple and persuasive.

We have all seen clips on TV of a foundry, where a huge bucket of yellow-hot liquid steel is poured into a mold. It looks great, there is hot liquid metal splashing everywhere. This makes great, dramatic, TV. But very poor castings. If metal turbine blades for aeroengines were made like this (they aren’t) as soon as the engine spun up to speed the blades would shatter and they’d be bits of broken metal blade flying everywhere. Messy.

The reason is simple. Pouring and splashing a liquid tends to fold air into the metal. This is just what a chef does when they need dough. But dough benefits from air being folded into it – it makes the bread lighter. However, microscopic air pockets in metals are a disaster. They get trapped in the crystallised metal and then weaken the final metal object. Solids break at their weakest point, so introducing weak points – the air pockets – is just what you don’t want to do.

So that is what I have learned this morning. Another speaker mentioned the ‘mushy zone’. I did not quite catch what that was, although I think it can be important, and it sounds fun. Anyway, next up I am following my colleague Paul Stevenson‘s example and going up north for a conference. On Sunday I am off to Leeds.

* Sadly, that pun was attended.

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