Effect of manganese pre-partitioning process on the microstructure and mechanical properties of low carbon dual phase steel

Abstract

A low carbon (0.11 wt.%) steel with 1.78% Mn was subjected to pre-partitioning quenching and partitioning (PQ&P), quenching and tempering (Q&T), quenching and partitioning (Q&P) to develop ferritemartensite dual phase (DP) steel. The study suggested that all the treatments resulted into ferrite, martensite (or tempered martensite) and retained austenite microstructure. The amount of retained austenite was ∼ 5%, when the steel was treated by PQ&P process with partitioning time of 100 s, because of Mn pre-partitioning stage increased in the stability of retained austenite. But only ∼ 1% for Q&T and Q&P processes. With the increase of partitioning time from 10 to 100 s in the PQ&P process, the amount of retained austenite was increased, the tensile strength decreased, and yield strength and elongation were both increased. Among the different heat treatment processes, PQ&P sample clearly yields most attractive combination of strength and ductility compared to Q&T and Q&P samples. The experimental steel after pre-partitioning quenching and partitioning (PQ&P) process had higher uniform elongation of 16.3% and strength-ductility balance (UTS Â TEL) of 17013 MPa.%. In contrast to conventional Q&T process, 27.3% higher uniform elongation and 7.4% greater strength-ductility balance were obtained.Keywords: dual-phase steel / quenching and partitioning / microstructure / mechanical properties / retained austenite *