Investigations were carried out on aging of a HSLA-100 steel containing Cu as the major alloying element and Nb, Ti and V as microalloying elements. The aging process after varying amounts of cold deformation was followed by hardness measurements and microstructural changes were studied using light and electron microscopy. Presence of Ti activates the formation of (Nb, Ti)C precipitates and completely suppresses the precipitation of Cu. Even a solution treatment at 1100° C is not sufficient to completely dissolve Nb and Ti in the matrix and undissolved (Nb, Ti)C precipitates were observed in oil quenched state. Strain induced aging at 400°C causes simultaneous coarsening of existing precipitates and nucleation of fresh carbides, which results in multi-stage hardening in this steel. Strong precipitate-dislocation interactions cause retardation in recrystallization of deformation structure leading to retention of high hardness levels even on prolonged aging.
Volume 42 | Issue 6
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