Can Hitting Metal Make it Magnetic?

[Th3Proj3ct]

If you take a screwdriver for example, and hit it a few times near the tip with a hammer or something hard; why does the screwdriver become magnetic?
I was shown someone doing this, and shortly afterwards it was able to attract nails or screws around.

 

[berkeman]

I've never seen this. Maybe the head of the hammer was magnetized. If anything, hitting a magnetized object generally weakens it magnetization.

 

[Danger]

Actually, we used to do it once in a while just for fun. The metal rod or whatever has to be aligned with magnetic north. It seems that the vibrations loosen up the magnetic domains enough that they react to the Earth's field and turn around. The effect is very weak, though.

 

[berkeman]

Actually, we used to do it once in a while just for fun. The metal rod or whatever has to be aligned with magnetic north. It seems that the vibrations loosen up the magnetic domains enough that they react to the Earth's field and turn around. The effect is very weak, though.

Ahh, interesting. Thanks for that Danger! I would have never thought of that. Learn something new every dang day here on the PF!

 

[Danger]

Wow... I never thought that I'd get one over on you, especially in this area.

 

[berkeman]

Wow... I never thought that I'd get one over on you, especially in this area.

Pppffffttttt! They don't call you Danger for nothing!

 

[Andy Resnick]

If you take a screwdriver for example, and hit it a few times near the tip with a hammer or something hard; why does the screwdriver become magnetic?
I was shown someone doing this, and shortly afterwards it was able to attract nails or screws around.

Searches using "work hardening", "plastic deformation" and magnetization did yield a large number of articles, for example:

http://ieeexplore.ieee.org/iel5/20/19613/00908685.pdf?arnumber=908685

But I could locate a clear discussion of the subject.