For multiphase steel, an efficient and accurate quantitative analysis of constituent phases is critical in understanding the mechanical mechanism and optimising its properties. A method based on image digitisation and the concept of categorised linear interception has been proposed to study the amount of retained austenite (RA) residing in different phases in quenching and partitioning treated multiphase steel. It was found that RA at different locations transformed in different strain stages due to considerable influence from the surrounding phases, and the stability of each type of RA was estimated according to the above mentioned method. The proposed multistage transformation was proved to be more accurate than a single stage stability model.
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