MICROSTRUCTURE AND TENSILE PROPERTIES OF A RECENT INTER-CRITICALLY AUSTENITIZED QUENCHED AND PARTITIONED STEEL

Quenched and partitioned steel is a promising grade of advanced high-strength steel "Third Generation" for industrial applications such as the automotive industry. This research aimed to develop a novel ultra-high-strength quenched and partitioned steel with good ductility from a novel alloy with the composition of 0.37C- 3.65Mn- 0.65Si- 0.87Al- 1.5Ni-0.05P, wt.% which is non-standard. This quenched and partitioned steel was developed by inter-critical austenitization followed by quenching to a temperature below Martensite start temperature (80 and 120 oC), then partitioning at 450 oC for different times (20, 40, 60, 100, 140, and 180 s). Scanning electron microscope and X-Ray diffraction were utilized to investigate the microstructure and retained austenite characteristics. The tensile properties of developed Q&P specimens were also investigated. The results demonstrated that the specimen quenched at 120 oC and partitioned for 180s achieved a maximum strength elongation balance of 26 GPa.%. Both the specimens quenched at 80 and 120 oC displayed a decrease in strength values with extending holding time due to the tempering of primary martensite. Increasing partitioning time for the specimens quenched at 120 oC led to enhancing elongation, where a maximum total elongation of 19.7% was achieved for the partitioning time of 180s.