The impact of periodic distribution of alloying elements during tempering in a multistep partitioned manganese steels on mechanical behavior: Experiments, simulation and analysis

Abstract Restricting carbide formation during tempering is desired from the perspective of high stability of retained austenite in steels. A periodic distribution of high Mn-low Al and low Mn-high Al region was induced in a multi-step partitioning (MSP) quenching process, providing a new pathway to control the precipitation behavior during tempering, which has a broad scope in the microstructural design of steels. The MSP process involved innovative combination of intercritical annealing, flash process and tempering in the endeavor to obtain high strength-high ductility combination (yield strength ~ 694 MPa, tensile strength ~ 1078 MPa). The presence of retained austenite in MSP quenched steel, benefited from high Mn-concentration and led to partitioning of carbon from martensite to retained austenite during the early stage of tempering. High Al-content in the martensite region restricted the nucleation of carbides and promoted partitioning of carbon. During tempering, the growth of carbides in martensite in MSP quenched steel was governed by the competition of carbon between carbides and retained austenite, which led to rapid coarsening of carbides as compared to the conventional quenched steel. The periodic distribution of Mn and Al, which led to heterogeneous stability of retained austenite, led to unique TRIP effect in the MSP quenched and tempered steel, and characterized by high work hardening rate during the early stage of deformation.