鉄-りん合金の粒界破壊の炭素による抑制

概要

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Fe-P alloys with up to 0.67wt% phosphorus show intergranular fracture (IGF) by impact test after quenched from 1073K. Addition of carbon up to about 0.01wt% to the alloys prevents the intergranular fracture caused by the grain boundary segregation of phosphorus, and lowers the ductile-brittle transition temperature (DBTT). This effect is due to the segregation of carbon to grain boundaries. Aging at 873K of the quenched specimen with 0.52%P and 0.0008%C reduces DBTT and increases the degree of grain boundary segregation of carbon while it does not affect the degree of grain boundary segregation of phosphorus. The grain boundary segregation of carbon increases the grain boundary cohesion and prevents the intergranular fracture without removing phosphorus from grain boundaries. DBTT's of the Fe-P-C alloys are analyzed in terms of the degree of grain boundary segregation of carbon and phosphorus and the solution hardening by phosphorus (the bulk concentration of phosphorus). The site-competition between carbon and phosphorus is taken into account in the calculation of the degree of segregation. It is found that the increase in the boundary cohesion by the carbon segregation is and important factor to prevent IGF.
社団法人日本鉄鋼協会の論文
1984-12-01