Deformation Processing: Rolling, Forging and Extrusion

Forming changes more than geometry

Rolling, forging, extrusion and drawing alter dislocation density, crystallographic texture, grain shape and internal defect closure. The resulting properties depend on deformation temperature and strain path.

Cold, warm and hot working

Cold working increases strength through work hardening but raises forming load and reduces ductility. Hot working enables dynamic recovery or recrystallisation, lowers flow stress and can refine structure. Warm working occupies the useful middle ground for selected alloys.

Flow is not uniform

Friction, die geometry, redundant strain and thermal gradients create heterogeneous deformation. Dead zones, laps, centreline damage and surface cracking can emerge from poor process design.

Texture matters

Preferred crystal orientation can improve or harm formability, fatigue, magnetic response and anisotropy. Processing schedules are often designed to control texture as deliberately as dimensions.

Takeaway

Treat deformation processing as microstructure engineering under load, temperature and friction—not merely as shape change.