Grain structure of an austenitic stainless steel NF709 (25Cr20Ni). Many of the grains contain annealing twins. NF709 is a creep-resistant austenitic stainless steel used in the construction of highly sophisticated power generation units.
Transmission electron micrograph of type 302AA" austenitic stainless steel, cold-rolled and then annealed at 704 oC for one hour. Partially recrystallised microstructure. Recrystallised grains are clean (largely free from defects) whereas the deformed regions show a large concentration of defects. There are annealing twins in the recrystallised region. Shows a recrystallised grain which is relatively free of dislocations and contains annealing twins, surrounded by a deformed matrix which has a high dislocation density.