Re: Why would a metal ball not return to its original volume?

I asked several metallurgists about this and got no definite answer. 
We did come up with some ideas tho. The first question was is it still 
so? That there might be some hysteresis in the recovery of the metal.  
The next question was, Are you sure it's the ball that changed and that 
something hadn't accidently become deformed.  The metal should be 
examined,I don't know the material,and it is possible that a phase 
change was induced or the surface became oxidized or cracked thereby 
slightly increasing the volume.  Make some careful measurements and 
see what evidence appears.  My first guess is hysteresis and that they 
have fixed themselves by now.  If not careful measurements and 
observations are in order.