The Microstructure Evolution during Divorced Eutectoid Transformation in a κ-Carbide Reinforced High Specific Young’s Modulus Steel

High specific Young’s modulus steel reinforced by κ-carbides has the characteristics of high strength and low density, which introduces potential applications of this material in automotive parts with a stiffness requirement. In this work, a 780 MPa grade Fe-Al-C high specific Young’s modulus steel was developed, and the addition of high contents of carbon and aluminum introduced a large fraction of κ-carbides into the steel matrix. To improve the ductility of this steel, a divorced eutectoid transformation (DET) treatment was adopted to regulate the microstructure of κ-carbides. A detailed evolution of κ-carbide during DET was investigated by staged quenching and microstructure characterization. It has been found for the first time that the κ-pearlite transformation and κ-carbides precipitation were mainly completed in the early stage during slow cooling, and the spheroidization of κ-carbides was mainly completed in the later stage. In addition, the effect of DET parameters on the microstructure evolution was analyzed, and it was found that a better spheroidization effect of carbides can be obtained at a lower cooling rate.