During intercritical quenching and partitioning(IQ&P)treatment of high strength steel,element C tends to segregate towards retained austenite at low temperature partitioning stage,which can stabilize the retained austenite and improve its strength and plasticity.The ferrite+pearlite(F+P)high strength steel was subjected to IQ&P treatment.The microstructure,properties and C element partition of the high strength steel at low temperature were studied by means of scanning electron microscope,tensile testing machine and multi-function internal friction instrument.The results show that in the high temperature partitioning stage(two-phase intercritical quenching at 820 ℃ for 240 s),the microstructure is austenitized gradually,and then the martensite,M/A and carbide are formed during the quenching process.The product of strength and elongation and volume fraction of retained austenite are 14.4 GPa·％and 5.65％,respectively.During low temperature partitioning stage(at 350 ℃ for 300 s),tempered martensite is formed,M/A structure,retained austenite and cementite are retained.The product of strength and elongation and volume fraction of retained austenite are 18.6 GPa·％and 9.26％,respectively.C atoms interact with defect-type and movable edge dislocations at low temperature partitioning stage,forming Snoke peak and SKK peak,which increase the volume fraction of retained austenite and are the main reason for the improvement of the product of strength and elongation of the high strength steel.
IQ&P processadvanced high strength steellow temperature partitioningretained austenitemechanical propertiesC-partition
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