Study of cleavage fracture in ferritic stainless steels Part II: Cleavage micro-mechanisms and critical stresses

Cleavage fracture and the mechanisms involved in different ferritic steel model microstructures are investigated according to grain sizes, precipitates and solute atoms in the matrix. For each case, one of these parameters is varied. Estimation of the critical stress for cleavage was investigated and discussed: it is shown to be determined from a simple Griffith inspired analysis or by employing the Smith's description. The description to adopt depends on careful analysis of the involved mechanisms. This aims at better understanding the governing parameters of the Ductile to Brittle Transition Temperature (DBTT) and to suggest routes for alloys processing to reduce the DBTT in ferritic steels.