Interaction of phosphorus, carbon, manganese, and chromium in intergranular embrittlement of iron

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Abstract
Vacuum melted electrolytic iron and alloys of Fe–P, Fe–Mn, Fe–Cr, Fe–Mn–P, and Fe–Cr–P were employed in a study of the effects of chromium and manganese on phosphorus segregation and intergranular embrittlement. The effects of carbon were examined by hydrogen-decarburization of the original low carbon (10–60 ppm) alloys. The critical fracture stress was measured by pure bending of notched bars at 133 K, and the grain boundary compositions were measured by Auger electron spectroscopy. Manganese was found to segregate in the absence of phosphorus and to be a powerful embrittling element. Carbon was found to exert a great intergranular strengthening effect. It also interfered with the segregation of phosphorus; the latter effect was reduced by the presence of chromium, in agreement with the prior report of Erhart and Grabke. In decarburized alloys the presence of manganese caused increased phosphorus segregation but not when carbon was present at 10–30 ppm. Segregation of manganese and chromium were both increased by the presence of phosphorus. MST/500