Other material properties, such as corrosion resistance of some stainless steels under certain environmental conditions, are also compromised by the presence of s -phase. This series of articles describe the fundamentals and significance of sigma phase formation in stainless steels. Sigma phase formation was described in the first article. The second hot topic article described materials more susceptible to sigma phase effects and also described the role of compositional factors in sigma-phase formation. The third hot topic article described micro-structural factors that influence sigma phase formation.
Fracture toughness is defined as the ability or resistance of the material to crack advancement.
This property is generally measured by the application of a sudden load on a notched or pre-cracked sample. This form of testing is referred to as impact testing. The ductility of the material is similarly affected by the presence of s -phase. Ductility can be defined as the ability of the material to be plastically deformed without fracturing. This property is especially important for components that are configured into shape by successive forming operations.