Mechanisms for cleavage fracture in duplex stainless steels

摘要

Duplex stainless steels that have two phases with different mechanical and physical properties exhibit micro deformation heterogeneity and localized cracking or fracture in nature.In this study,the cleavage fracture behaviors in two super duplex stainless steels have been investigated in the following three conditions: at low temperatures,the material with spinodal decomposition and that with other precipitates and defects.By both impact toughness and fracture toughness tests,the ductile to brittle transition and cleavage behaviors have been investigated.The fracture is analyzed using a SEM with EBSD.The fracture mechanisms are focused; mainly the parameters or factors that cause the occurrence of cleavage in the materials.Since the austenitic phase in the material in these conditions is still tough,a coupling effect will be discussed to explain the cleavage in the austenitic phase observed.Local approach to fracture is used to assess or discuss the influence of local hardness,precipitates and stress concentration on the formation of cleavage fracture in the materials in different conditions.