2008 Volume 48 Issue 8 Pages 1122-1125
Yield strength was investigated in iron with different grain size and different contents of carbon and nitrogen. The Hall–Petch coefficient; ky is originally very small in high purity iron (about 100 MPa·μm1/2) but it increases with increasing the amount of solute carbon content. The value of ky is enlarged to around 550 MPa·μm1/2 by 60 ppm of solute carbon and levels off at around 600 MPa·μm1/2 in the region above 60 ppm solute carbon. On the other hand, nitrogen hardly influences the ky 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.