Evidence of Strain-Induced Precipitation on a Nb- and N-Bearing Austenitic Stainless Steel Biomaterial

摘要

The kinetics of static recrystallization of a niobium- and nitrogen-bearing austenitic stainless steel, 22Cr-10Ni-3.5Mn-2.5Mo-0.4Nb-0.35N, was studied. The recrystallization kinetics were studied through the metallographic analysis of specimens submitted to hot torsion tests. The samples were strained to ε = 0.3 with a strain rate of 1 s~(-1) at temperatures ranging from 1000 ℃ to 1200 ℃ and delay times ranging from 0.1 s to 900 s. The recrystallized fractions as a function of temperature and delay time after the deformation were measured and these indicated that the material only recrystallizes completely at T ≥ 1100℃. At T ≤ 1050℃, the recrystallized fractions that were measured did not exceed 16 %, even for delay times as long as 900 s. Multipass torsion tests under continuous cooling conditions were carried out and strain-induced precipitation of the Z-phase was seen. The inhibition of the static recrystallization took place for T < 1110℃. Based on this evidence, the grain refinement brought about by recrystallization controlled processing and conventional controlled processing were assessed.