Metallographic study of phosphorus segregation in interstitial free sheet steel

Cold work embrittlement (CWE) of rephosphorized interstitial free sheet steels is sensitive to prior annealing treatment. In the current work a comparison has been made of P segregation in batch and continuously annealed materials for one grade of steel. The detailed grain boundary structures and local chemical compositions have been studied by TEM, EDS and EBSD. Mechanical tests have been performed to link the local chemical composition and grain boundary structure to the mechanical properties. The results indicate that P segregation and the mechanical properties depend on the grain boundary structure and that P segregation is more complete in the batch annealed material. Thus control of grain boundary structure may provide a future mechanism for amelioration of CWE.