4 - Iron Alloys

Abstract

In this chapter iron alloy is treated in the same way as nickel alloy, since the electronic approach does not require any distinction between ferrous and nonferrous alloys. Pure iron transforms from a body-centered cubic (bcc) lattice to a face-centered cubic (fcc) lattice at about 1185K. Two alloying parameters, Md and Bo, relevant to both bcc Fe and fcc Fe, are first determined from the electronic structure calculations. The bonding state of C, N, and O in fcc Fe is also presented since these interstitial elements play important roles in iron alloys. Furthermore, it is shown that the second nearest neighbor atomic interactions are significantly large in bcc Fe, as first pointed out by Pauling. However, this is not the case in those bcc metals (e.g., V, Cr, Nb) that do not transform from the bcc phase to the close-packed fcc or hcp phase at a certain temperature.