Enhanced Thermal Stability of the Low-Carbon Ultrafine Grain Steel with Nanoprecipitates

作者：Zhang, Qingxiao; Yuan, Qing^*; Wang, Zhoutou; Qiao, Wenwei; Xu, Guang^*

来源：Steel Research International, 2022, 93(1): 2100320.

DOI：10.1002/srin.202100320

• annealing
• precipitates
• recrystallization
• tensile strength
• thermal stability

Niobium (Nb), a microalloy element, is purposefully added to improve the thermal stability of ferrite grains in a low-carbon ultrafine grain (UFG) steel. Results manifest the excellent thermal stability in the Nb-UFG steel with 0.028 wt% Nb addition by providing favorable kinetics and thermodynamic stabilization effects. The almost unchanged grain size and mechanical properties of Nb-UFG steels annealed for 45 and 180 min at 500 degrees C are simultaneously obtained by the heterogeneous ferrite grains, NbC precipitates, and geometrically necessary dislocations (GNDs) mainly formed during tensile tests. The imperceptible change in size and volume fraction of NbC particles of the two Nb-UFG steels annealed at different time are attributed to the inherent thermal stability of NbC and main precipitation pattern of NbC particles from the alpha phase.