Effect of Interstitial Elements on Hall–Petch Coefficient of Ferritic Iron

Abstract

Yield strength was investigated in iron with different grain size and different contents of carbon and nitrogen. The Hall-Petch coefficient; k y is originally very small in high purity iron (about 100 MPa mm 1/2 ) but it increases with increasing the amount of solute carbon content. The value of k y is enlarged to around 550 MPa mm 1/2 by 60 ppm of solute carbon and levels off at around 600 MPa mm 1/2 in the region above 60 ppm solute carbon. On the other hand, nitrogen hardly influences the k y value. The mechanism of the change in Hall-Petch coefficient was then discussed in terms of the grain boundary segregation of carbon and nitrogen atoms.