Materials engineering — strengthening by deformation: The increase in hardness and strength produced by plastic deformation at room (or low) temperature is called

Introduction / Context:
Many manufacturing processes intentionally deform metals below recrystallisation temperature to improve strength and hardness. Understanding the terminology and mechanism of this strengthening method is fundamental for process planning (e.g., rolling, drawing, bending) and for deciding when to anneal between passes.

Given Data / Assumptions:

• Plastic deformation at room or moderately elevated temperatures.
• No phase transformation or diffusion-based ageing is involved during the deformation itself.
• Material is typically a ductile metal such as steel, aluminium, or copper alloys.

Concept / Approach:
Work-hardening (also called strain hardening or cold work) increases dislocation density. Interactions among dislocations impede further movement, raising the flow stress, yield strength, and hardness while reducing ductility. The effect can be reversed or reduced by recovery and recrystallisation during subsequent annealing. This is distinct from age-hardening (precipitation hardening), which depends on controlled heat treatment that forms fine precipitates to impede dislocations, and from surface hardening methods like induction or flame hardening that transform only surface layers by rapid heating and quenching.

Step-by-Step Solution:
Apply plastic strain below recrystallisation temperature to raise dislocation density.Increased dislocation interactions elevate yield and hardness.Recognise the trade-off: ductility and toughness decrease with cold work.Therefore, the correct term for hardness increase by deformation is work-hardening.

Verification / Alternative check:
Tensile tests on cold-rolled vs. annealed samples show higher yield strength and lower elongation for the cold-worked material, confirming strain hardening.

Why Other Options Are Wrong:
Age-hardening requires solution treatment and ageing, not immediate deformation.

Induction and flame hardening are thermal surface treatments relying on martensitic transformation in steels.

Solution strengthening depends on solute atoms in solid solution, not on deformation alone.

Common Pitfalls:
Overworking without intermediate anneals, leading to cracking; assuming work-hardened parts retain ductility; forgetting springback increases with higher strength after cold work.

Final Answer:
work-hardening