Understanding Precipitation Hardening in Metal Strength

[alexparker]

Hi guys, I am doing a powerpoint on the hammer, and i need to say something about precipitation hardening, and I am having a bit of trouble understanding it. could someone please explain it simply

Thanks

 

[Mapes]

What level of explanation are you looking for?

When we use metal tools, we usually want them to stay the same shape; we don't want them to permanently deform. Deformation in metals occurs by atomic planes slipping or shearing past each other, but the process doesn't occur with an entire plane at once; rather, a 1-D defect called a dislocation moves through the metal. Like a bump in a rug that you would kick across the floor, a dislocation carries permanent deformation through a crystal. Thus, a useful strategy for strengthening metals is to inhibit dislocation motion. One way to do this is to put a particle of a second material in the way, and a viable way of doing that is to precipitate it; that is, to nucleate and grow the particle during thermal processing. Generally, the dislocation won't easily move through the particle, and will have to bow around it or cut through it. The precipitate thus inhibits dislocation glide and makes the metal harder.

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