3D atom probe characterization of temporal evolution of precipitates in aging Nb-V micro-alloyed steel

摘要

A 3D atom probe combined with TEM was applied to characterize carbides precipitation in Nb-V microalloyed steel aging at 550 °C for different times after being water-quenched from 1200 °C. The results indicated that the V- and Nb-containing ultra-fine carbides obtained by 4 h aging had the highest number density and moderate sizes, resulting in a peak precipitation strengthening value. C, V and Nb firstly co-segregated to form nano-sized clusters at the initial stage of precipitation, and then contributed to the formation of composition-steady carbides as the aging time was prolonged.