Carbonitride precipitates during deformation of undercooled austenite in Nb-microalloyed steel
CHEN Guoan, YANG Wangyue, GUO Shouzhen, SUN Zuqing Materials Science and Engineering School, University of Science and Technology Beijing, Beijing 100083, China The State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
By using TEM the strain-induced precipitation of Nb(CN) during deformation of undercooled aus-tenite was investigated in Nb-microalloyed steel. The results showed that at 1200℃ all of Nb were dissolved and there were no Nb(CN) precipitates formed during cooling until down to 760℃. During deformation-enhanced ferrite transformation the Nb(CN) of dynamic precipitation required an incubation period, but compared with isothermal transformation it reduced significantly. Only when the strain increased to 0.69, Nb(CN) began to precipitate on dislocation nodes and grain boundaries. The volume fraction of Nb(CN) precipitates increased with increasing strain but their coarsening was not significant. It is shown that the measured grain size is in good agreement with the calculated value.