Controlling Carbide Evolution to Improve the Ductility in High Specific Young’s Modulus Steels

A high specific Young’s modulus steel could be achieved by introducing a large fraction of kappa-carbides ( κ -carbide), and its ductility was improved by efficiency divorced eutectoid transformation (DET) treatment. For this steel, carbon and aluminum contents affect not only the carbide fraction, but also the type and morphology of carbides, and consequently the mechanical properties. In this work, the alloy was designed by considering both the carbide morphology and Young’s modulus, and the carbides in the high specific Young’s modulus steels were adjusted by controlling carbon content in a suitable range for achieving a good combination of strength and ductility. The detailed microstructure evolution process during DET reaction was studied, and it was found that a higher austenitizing temperature and the cooling rate lower than 300 ℃ h −1 are suitable. The blocky carbides could be avoided by designing the carbon content in a limited content range. The microstructure-property relationship of the experimental steels was also discussed for giving an impetus to the future development of high specific Young’s modulus steels.