FINE STRUCTURE AND CRYSTALLOGRAPHY OF THE MICROSTRUCTURES IN A NORMALIZED 55SiMnMo STEEL
55SiMnMo钢正火组织的精细结构和晶体学特征

The microstructures produced in a normalized 55SiMnMo steel consisted ofcarbide-free upper and lower bainite,martensite and retained austenite.Both the upperand lower bainite contained midribs,subunits and dislocations;the martensite was twinned;and the retained austenite comprised a high density of dislocations.The measured habitplane and orientation relationship of the bainite with the aurstenite suggested a shearmechanism by which the bainite was nucleated.The formation of the bainite subunits wasexplained in terms of the carbon enrichment of the retained austenite and the plastic relaxa-tion of the elastic strain energy,both occuring at the bainite/austenite interfaces.