Improving mechanical properties and retained-austenite stability of a medium carbon Q&P steel by adjusting phase ratio

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Original languageEnglish
Article number142580
Journal / PublicationMaterials Science and Engineering A
Online published30 Dec 2021
Publication statusPublished - 26 Jan 2022


In this study we explored mechanisms for improving the mechanical properties and retained-austenite (RA) stability of a Q&P steel by adjusting the phase ratio. With increasing annealing temperature, the yield strength of the steel increased and the ductility firstly increased and then decreased. These observations are closely related to the specific phase constituent and retained austenite stability produced by the Q&P process. The hard phase (tempered martensite, bainite, martensite-austenite island/secondary martensite) fraction increased with increasing annealing temperature, and the RA size and morphology changed from large, blocky to small, blocky and lath-like. At 800 °C, the phase ratio of RA, bainite, ferrite, and initial martensite is 2:1:2.2:2, which produced the superior combinations of yield strength (σy), tensile strength (σTS), and ductility (δ) (e.g. σy = 960 MPa, σTS = 1450 MPa, δ = 28%; or σy = 1320 MPa, σTS = 1540 MPa, δ = 14%). The superior mechanical properties are attributed to the coordinated deformation between hard phase and soft phase and TRIP effect.

Research Area(s)

  • Mechanical properties, Phase ratio, Quenching and partitioning process, Retained austenite