Annealing effects on microstructure and mechanical properties of cryorolled Fe-25Cr-20Ni steel

Annealing effects on microstructure and mechanical properties of the cryorolled Fe-25Cr-20Ni austenitic stainless steel were investigated by means of optical, scanning and transmission electron microscopy, X-ray diffraction, microhardness and mini-tensile testing. After 90% cryorolling, the grains of austenitic stainless steel were refined to the nanometer scale, and the nano-level grain size increased to the submicron scale after subsequent annealing. The recrystallization temperature of the cryorolled Fe-25Cr-20Ni steel was about 730 degrees C. After annealing for 10 min at 800 degrees C, the microstructure was fully recrystallized, and the grain size was about 500 nm. The growth of recrystallization grains occurred with further annealing temperature increase. After annealing for 10 min at 1000 degrees C, the grain size increased to about 2 gm. Meanwhile, the elongation was nearly the same as the original un-deformed sample, but the yield strength and tensile strength is 2.3 and 1.5 times of the original un-deformed sample, and the toughness increased:by 27%. Tensile fracture morphology changed from a mixture of quasi-cleavage and ductile fracture (before annealing) to typical ductile fracture (after annealing).