3D atom probe characterization of alloying elements partitioning in cementite of Nb-V microalloying steel

Three dimensional atom probe (3DAP) combined with SEM and TEM was applied to characterize the alloying elements segregation in cementite of experimental steel tempered at 450C for 4 h after solution treatment at 1200C for 0.5 h. The results indicated that in the as-quenched specimen the alloying elements V, Nb, Si, Mn, Mo and Al are homogeneously dissolved in matrix, and element C slightly segregates due to autotempering. A significantly segregated zone of C in the 450C tempering specimen was detected as a cementite, in which exists a zone enriched with Mn and slightly segregated Mo and V. Si is prone to segregate at cementite/matrix interface. A monolayer enriched with C and V was also detected, which may be a V4C3 based G.P. zone acted as an initiate precipitation of alloying carbides during tempering.