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Influence of multiphase on the strain hardening behavior of 60Si2CrVAT spring steel treated by a Q–P–T process

Jiang, Yun, Liang, Yilong, Yin, Chunhong, Long, Shaolei, Zhao, Fei, Xiao, Yu
Journal of materials science 2018 v.53 no.14 pp. 10396-10410
deformation, microstructure, steel, temperature
A strong strain hardening ability in ultra-high strength spring steel 60Si2CrVAT was achieved by the design of multiphase microstructures using a quenching–partitioning–tempering process. The microstructure consisted of ~ 70% martensite/bainite and ~ 30% retained austenite, which was obtained at an optimized partitioning temperature of 380 °C. The corresponding yield strength ratio and the product of strength and elongation were 0.81 and 34,828 MPa%, respectively. Interestingly, this sample exhibited a double-stage strain hardening characteristic with a concave-down shape, which was distinct from that of the other samples. The excellent performance of the ultra-high strength spring steel was mainly due to the interactions between the multiple phases and the stability of the retained austenite during cold deformation. This paper provides a new way of obtaining a strong strain hardening ability in ultra-high strength steels, which is expected to be applicable to the cold coiling process.