Mechanical Engineering - Production Engineering - Discussion

WORK-HARDENING: Toughen a metal as a result of COLD-WORKING.

When these metals are cold worked, permanent defects change their crystalline makeup. These defects reduce the ability of crystals to move within the metal structure and the metal becomes more resistant to further deformation. The resulting metal product has improved tensile strength and hardness, but less ductility.

Can anyone justify?

Work hardening means change in micro structure which make the chip brittle so with a little amount of cutting force it breaks.

We also know that less ductility means more discontinuous chips. Like castiron, which is less brittle. How it can be work hardening?

I think ductility should be the answer because during chip formation its the extent of ductility of the material being machined that determines whether the chip formed will be continuous, discontinuous or built up the edge.

Chip breakers are used in a tool which is used for machining a ductile material because we all know that during the machining of ductile materials continuous chip is formed and this may causes crater wear or formed BUE therefore a chip breaker is required.

Work hardening means strength of material increases and losses it's ductility so chips are a break.