Microstructural development during rolling was compared in two Hadfield steels; one having a low carbon content (0.65wt%) and the other a high content (1.35wt%). Differences in sub-structure were observed which were due not to small changes in stacking-fault energy, but to carbon segregation which occurred in the low-carbon steel (via vacancy diffusion) but not in the high-carbon steel. This was demonstrated using Mossbauer spectroscopy and was in agreement with systematic characterizations of microstructures using optical and transmission electron microscopy. In the low-carbon steel, mixed microstructures were formed which contained intrinsic stacking faults, deformation twins and brass-type shear bands. In the high-carbon steel, mixed sub-structures of dislocation tangles, deformation twins and shear bands (both copper and brass type) developed. In spite of the differences in sub-structure development during rolling in the two steels, the difference in stacking-fault energy was small: approximately 2mJ/m2. That is, less than 10% of the stacking-fault energy.

Influence of Carbon on Development of Deformation Microstructures in Hadfield Steels. T.N.Kim, A.J.Bourdillon: Materials Science and Technology, 1992, 8[11], 1011-21