摘要
Dynamic recrystallization(DRX)plays significant roles in manipulating of microstructures during hot deformation and the result mechanical properties;however,the underling mechanism leading to multi scale-microstructures remains poorly understood.Here,the DRX mechanism under wide processing conditions(i.e.950-1200°C,0.001-10 s-1)in Incoloy 028 alloy was investigated,where the relationships among flow stress,Z parameter and grain size,as well as the evolution of characteristic microstructures(grain size,sub-grain boundaries,and high angle grain boundaries),are established.As the values of Z parameters decrease(corresponding to decreased flow stresses),three typical softening mechanisms successively occur,ranging from continuous DRX controlled by dislocation glide,discontinuous DRX dominated by dislocation motion(climb and cross/multiple slip)and grain boundary migration,to dynamic normal/abnormal grain growth resulting from grain boundary migration,with transition regions where two adjacent mechanisms occur simultaneously.Correspondingly,these above three softening mechanisms result in ultrafine,fine and coarse grains,respectively.The present findings demonstrate a comprehensive understanding of DRX mechanism over a wide range of processing conditions,and further provide a new guideline for preparing single crystals.
基金
This work was supported by the National Key R&D Program of China(grant numbers 2017YFB0703001,2017YFB0305100)
the Natural Science Foundation of China(grant numbers 51431008,51790481,51804336,51901185)
the Research Fund of the State Key Laboratory of Solidification Processing(grant numbers 2019-BJ-04,2019-TZ-01)
and the Natural Science Basic Research Plan in Shaanxi Province of China(grant number 2019JM-132).We would like to thank the Analytical&Testing Center of Northwestern Polytechnical University for EBSD and TEM experiments.
