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The influence of substitutional atoms (Mn, P, Si, Al, Cr, Co) on the C Snoek peak in b.c.c. iron was investigated. In the dilute range of the substitutes, the addition of Co, Mn, Cr, Si, P and Al resulted in the decreases in Snoek peak height in this ascending order. However, the addition of Mn to the Fe–C–P alloy hardly changes Snoek peak height. There is even a case that Snoek peak height is increased by further Mn addition to this alloy. They can be explained systematically by the proposed model wherein the solute carbon present in the influence region where the lattice distortion around the substitute is greater than the threshold value cannot contribute to the Snoek peak. The strain field generated by a substitutional atom due to the difference in atomic size is concluded to be the main reason for the reduction in Snoek peak height.

The influence of P on the solubility of C in ferrite in equilibrium with cementite was investigated with low-carbon steels containing P ranging from 0 to 0.21 mass% over a temperature range from 573 to 973 K. The solubility of C was determined from internal friction measurements and infrared analysis of C using high frequency combustion technique. It has been found that P increases the solubility of C but decreases the Snoek peak height. The experimentally determined proportionality constant K in the equation, Sol.C (mass ppm)=K×Q -1 max (10 -4 ) increasing P content