Strengthening mechanisms in metals

Anything that makes it harder or slower for dislocations to move will strengthen a metal. Therefore, we can employ grain size reduction, alloying, and cold working to make metals stronger. This gives rise to Hall-Petch relation and other important tools for customizing mechanical properties of alloys.

[@nguyentu1998]

This is what I've been looking for. Excellent explanation

[@TaylorSparks]

Happy to help!

[@maryamtgh6029]

Thanks for your time, it was so useful and clear.

[@ivanvalverde7018]

Thank you

[@stevenalex4059]

thank you very much sir! your explanation is clear and this video has been very helpful.

[@TaylorSparks]

Nice. Glad it was useful for you.

[@FearNoSteel]

Cool video, could we get a video about the strengthening mechanisms inside of individual vanadium carbides at atomic level inside of a tool steel?

[@TaylorSparks]

Would love to. I might be teaching a ceramics course again soon.

[@FearNoSteel]

@@TaylorSparks that would be awesome, I find it to be a very curious subject and relevant to my work with all the knives I make especially with some steels that have MC volume at +20% volume

[@vishank7]

Absolutely amazing! I finally understood dislocation pinning, thanks a ton! I've got one doubt in the cold working section tho: When we cold work on a material, arent we pushing the dislocations to the grain boundaries and hence eliminating them? I thought the lesser number of dislocations left caused the strength to increase. Can you please explain how exactly we create new dislocations by cold working? Also, if the dislocations are randomly distributed, why would there be a net repulsion?

[@TaylorSparks]

I'm so glad it's helped, and to answer your question, yes and no. When we deform a material we generate many many dislocations. Some of those dislocations travel to grain boundaries and produce deformation, but not all. Therefore there is a net increase in dislocation density not a decrease.

[@vishank7]

@@TaylorSparks Thanks for the clarification! Why would they repel on average tho?

[@TaylorSparks]

@@vishank7 on average they repel because they have to be lined up exactly perfect to cancel out. If they are not lined up perfectly then they have an overall net repulsion. Since there are many more ways that they can be lined up imperfectly this leads to net repulsion

[@vishank7]

@@TaylorSparksAwesome, that makes sense! Can you please also make a vid explaining how precipitates interact with these dislocations?

[@TaylorSparks]

@@vishank7 I'm not sure if I will have time this year because I've already moved on to the next chapter. However, in principle it's not very different. if you precipitate out some other phase then this will also have a strain field around it. The strain field will interact with the strain field of view dislocations and pin them making it harder and stronger

[@miloszivkovic6118]

Well, why noone explains how this works in practise, do you anneal multiple times after single high deformation, or you forge and anneal in cycle? Also what determens how many new grains will grow from big old deformed one or on its expense?

[@trivikramaraju]

good

[@peterndungu3615]

We want more...

[@TaylorSparks]

Yes, whole courses can be taught on this topic! I hope to get a chance to cover them in greater detail. We cover them a bit more here ruclips.net/video/adCn-Yh84T4/видео.html

[@asanajohnson5386]

Still don't get it, when you add an atom of any size it should cause some form of compression due to you adding it, so adding small atoms to a crowded lattice, would just make it more crowded? I was thinking that the line of dislocation moves instead of you placing the small atoms in a crowded area