Crystallography of Martensite in Friction-Stir-Welded 12Cr Heat-Resistant Steel

Abstract

In this work, electron backscatter diffraction (EBSD) was applied for examination of the crystallography of the martensitic structure produced during friction-stir welding (FSW) of 12Cr heat-resistant steel. The martensitic transformation was found to be governed by the Kurdjumov–Sachs (K-S) relation, viz. {111}γ || {110}α′ and 〈110〉γ || 〈111〉α′, was characterized by substantial variant selection and led to considerable orientation spread within the martensite variants. Due to the latter effect, the K-S model was found to be ineffective for the reconstruction of prior-austenite grain structure. Instead, the mixed orientation relation, viz. {111}γ || {110}α′, 〈110〉γ || 〈111〉α′, and 〈112〉γ || 〈110〉α′, was shown to be more suitable for this purpose.