Effects of plastic deformation on carbide precipitation in steel

Abstract

The influence of plastic deformation on carbide precipitation in carbon steels containing 0.47, 0.74, and 0.88% carbon has been studied, using electron microscopy and magnetic analysis. Cold-work restrains precipitation in quenched steels: in a sufficiently deformed medium-carbon martensite normal precipitation of the ϵ-carbide in the first stage of tempering can be suppressed and, on heating above 200°C, the precipitation of cementite is hindered. If a steel is first tempered to precipitate an iron carbide and then deformed, the precipitate will tend to redissolve in the cold-worked matrix. Metallographic evidence of such a partial re-solution of an ϵ-carbide precipitate has been obtained in a steel tempered to the end of the first stage before deformation and subsequently aged at 130°C. Possible evidence of a similar, but appreciably smaller, solution effect was found in steels containing fine particles of cementite. It is suggested that these effects are a consequence of the strong interaction between carbon atoms and lattice defects in iron.