Microstructural changes taking place during the thermo-mechanical processing and cold working of steel 18Cr18Mn0.5N

Microstructural processes taking place during cold deformation were investigated using optical and transmission electron microscopy. Different interactions which contribute to the strengthening, i.e. slip/slip, slip/twin and twin/twin interactions, were observed with the following results: the partial dislocations were produced at twin boundaries, packets of stacking faults and consequently twins were formed by slip of partials. The high density of glissile dislocations and twins and the large number of their possible interactions resulted in high strength, ductility and toughness. The mechanical properties were improved further by the refinement of austenite grains using high temperature thermo-mechanical processing. Strain ageing of deformed steel before high temperature annealing did not influence recrystallization processes and did not decrease the grain size.