Due to the largely inhomogeneous deformation among constituent phases, the advanced high-strength multi-phase steels are always facing challenges when applied to automotive parts where local formability is critically ...Due to the largely inhomogeneous deformation among constituent phases, the advanced high-strength multi-phase steels are always facing challenges when applied to automotive parts where local formability is critically required. In this work, two characteristic microstructures were produced from a low carbon Ti-V microalloyed steel by varying the cooling path. In the ferrite single-phase microstructure resulted from "ultra-fast cooling(UFC) + furnace-cooling(FC)", the hole-expanding ratio of 200% and tensile strength of 647 MPa were achieved. In the ferrite-bainite-martensite(F+B+M) multi-phase microstructure produced by "UFC + air-cooling(AC) + UFC", the ferrite has been strengthened by Ti-V carbides to promote the strain partitioning, which resulted in the tensile strength of ≥780 MPa, a moderate elongation and hole-expanding ratio of 93%. The strengthening contributions of Ti-V carbides were calculated to be 126 MPa and 149 MPa in the ferrite single-phase and F+B+M multi-phase microstructure, respectively.展开更多
基金Funded by the National Natural Science Foundation of China(51204048)the Fundamental Research Funds for the Central Universities(N150704006)
文摘Due to the largely inhomogeneous deformation among constituent phases, the advanced high-strength multi-phase steels are always facing challenges when applied to automotive parts where local formability is critically required. In this work, two characteristic microstructures were produced from a low carbon Ti-V microalloyed steel by varying the cooling path. In the ferrite single-phase microstructure resulted from "ultra-fast cooling(UFC) + furnace-cooling(FC)", the hole-expanding ratio of 200% and tensile strength of 647 MPa were achieved. In the ferrite-bainite-martensite(F+B+M) multi-phase microstructure produced by "UFC + air-cooling(AC) + UFC", the ferrite has been strengthened by Ti-V carbides to promote the strain partitioning, which resulted in the tensile strength of ≥780 MPa, a moderate elongation and hole-expanding ratio of 93%. The strengthening contributions of Ti-V carbides were calculated to be 126 MPa and 149 MPa in the ferrite single-phase and F+B+M multi-phase microstructure, respectively.
