Abstract:
A steel of composition Fe-0.2C-3Mn-2Si-0.5Al was fully austenized followed by a quench and
partitioning heat treatment process (Q&P). The quench temperature was varied, which resulted in different volume
fractions of retained austenite (RA) and martensite. Analysis of the phase evolution and the resulting
microstructures during the Q&P process were carried out using different techniques namely, - dilatometry, FEG
SEM, EBSD, and neutron diffraction. Mechanical properties were evaluated by standard tensile tests on samples
quenched to different temperatures. The partitioning process was evaluated by dilatometry. The volume fraction
of the RA was determined by neutron diffraction. It was found that the volume fraction of RA increased with an
increase in the quench temperature contrary to the Speer model. It was also observed that the presence of bainite,
which formed during the quench and partitioning temperature significantly stabilized the RA by carbon
partitioning. The tensile test results indicated the optimum quench temperature for the best combination of strength
and ductility and contrary to expectation, this did not occur in the specimen with the maximum amount of RA. In
other words, the mechanical properties of the steel undergoing a Q&P process is influenced by the quench
temperatures and is also affected the phase evolution which occurs during both the quench and partitioning process.
