Micro-segregation of Phosphorus in a Fe-P-C Alloy Caused by Rapid α/γ Transformation

The mechanism of phosphorus segregation caused by rapid heating was clarified experimentally using Fe-0.6wt%P-0.3wt%C alloy. The alloy was heated rapidly up to 950℃ followed by quenching, and the phosphorus distribution was examined by EDX micro-analysis on the specimen consisting of austenite (martensite) and a little ferrite. As the result, phosphorus is enriched in ferrite region by rapid α/γ transformation in over ten times as much as its content of the bulk alloy. The rapid heating also brought a fall of the temperature of initiating liguation, which was confirmed by microscopic observation. Those experimental results could clearly prove the authors\u27 theoretical prediction that i)phosphorus is forced to enrich in the original ferrite, as it can be dissolved only a little in austenite produced by a arpid transformation, ⅱ)the region in which ferrite transforms finally becomes the austenite grain boundary, the greater the phosphorus cocentration in the grain boundary, the lower the temperature of its liguation becomes. The procedure of determining the correlation curve of the intensity of Kα-p vs. phosphorus concentration is explained in detail