抄録
A martensitic transformation which was induced by large plastic deformation on austenitic stainless steel SUS304(similar to AISI304)is reversely transformed into primary austenite phase with grain size of about 1μm by annealing.One more such thermo-mechanical treatment is applied for SUS304 with fine microstructures, grain sizes are measured and superplastic behaviors are examined.The grain sizes are extremely hyper-fined below 500nm, and the maximum ductility over 400 pct and the strain rate sensitivity index(m)of about 0.45 are obtained at high strain rate of 1.8×10-3s-1.The changes of microstructure during deformation are observed and discussed under the tensile conditions exhibiting the maximum elongation by using a transmission electron microscope.The same quantities of dislocation are seen at 200 pct and 300 pct deformation.The superplastic behaviors of SUS304 are accommodated to dynamic recrystallization.
