Work hardening is caused by what process?

• A. Repeated shaping
• B. Heating
• C. Oxidation
• D. Applying coatings

Answer: (A)

Work hardening happens when metal is deformed plastically at relatively low temperatures. As you shape the metal repeatedly, dislocations multiply and tangle, creating barriers that make further dislocation movement harder. That increased resistance to deformation raises the metal’s hardness and yield strength, though it reduces ductility. Heating can reverse this by allowing dislocations to rearrange or cancel out (annealing), lowering the hardening effect. Surface processes like oxidation or applying coatings don’t create the bulk dislocation structures needed for work hardening, so they don’t cause this strengthening. Therefore, repeated shaping best explains why work hardening occurs.