The dissolution behavior of σ-phase and the plasticity recovery of precipitation-embrittlement super-ferritic stainless steel

Abstract

In this study, a dissolution heat treatment was applied planning to recover the plasticity of an embrittled super-ferritic stainless steel caused by the precipitation of σ-phase, χ-phase and Laves phase. The dissolution behaviors of the brittle precipitation phase, and the concerned grain coarsening phenomena, as well as their effects on the mechanical properties were investigated. It was observed that the χ-phase dissolved first then did the σ-phase and therefore the Laves phase. The σ-phase dissolution kinetics showed a strong dependence on the reheating temperature. A weak grain growth phenomenon was found during the reheating process at 1100 °C. The Laves phase re-formation was observed during reheating at 1000 °C–1050 °C, which was generated by the Nb and Mo atoms diffusion. The plasticity of the tested steels was recovered after dissolution treatment at the temperature range of 1050 °C–1100 °C, during which the fracture mode was remodeled from brittle fracture to toughness fracture. The dissolution treatment at the temperature of >1050 °C was effective to recover the plasticity of precipitation- embrittlement SFSSs.