Anyone know the technical term for a ht steel returning to its set form after a force is applied? Ie "springiness" - like fixing a blade in a vice, bending it and its ability to return to form without deformation.

Elasticity? http://en.wikipedia.org/wiki/Elasticity_%28physics%29

I had thought of that, just wasn't sure if it exactly applied to the physical properties of steel and heat treating.

Flexability or Elasticity is a physical property describing material that has the ability or returns to it's orginal shape after being stressed.
My opinion is only a starting point. I am not a blade smith, they would most likely be of more help to you!

Resilience?

The resilience of the material is its ability to absorb energy without creating a permanent distortion.

http://www.mathalino.com/reviewer/mechanics-and-strength-of-materials/stress-strain-diagram

It is what is really being measured in a bearing drop test on an anvil.

Phil

Elastic deformation. The maximum point to which you can deform the piece before it will no longer return to shape is the elastic limit. After that you're in the plastic deformation range. (These are my rough, layman's definitions of terms that engineers and scientists define much more precisely.)