EFFECT OF TEMPERING ON THE MICROSTRUCTURE AND STRENGTH OF MARTENSITICALLY HARDENED PLAIN CARBON-STEELS

The X-ray interference line profile analysis was applied to plain carb on steels with less than or similar to 0.4 wt.% carbon after martensit ic hardening and tempering in order to investigate the mean strains an d domain sizes. From these parameters micro residual stresses and disl ocation densities have been estimated. The mean strains of the hardene d samples are only caused by the stress fields of dislocations. Temper ing leads to decreasing mean strains and micro residual stresses as we ll as increasing domain sizes due to rearrangements and annihilations of dislocations. The hardening contributions of dislocations and carbi de particles in the yield strength of the quenched and tempered states which increase with increasing carbon content, are evaluated. (C) 199 7 Elsevier Science S.A.