Crystallography of Maraging Steel: Influence of Variant Selection

Abstract

Abstract-In this work a study of the influence of variant selection on the crystallography after martensitic transformation in Maraging was studied.The study covered both the transformation under elastic deformation and also during plastic deformation. In Maraging steel, austenite becomes martensite at a temperature around 200 o C regardless of the cooling speed. To simulate the transformation during elastic deformation, a tensile test was performed in a furnace attached to a universal testing machine with an applied stress below the yield strength of the material. The specimen was heated to 850 o C, the furnace was opened and the sample cooled in air under a constant stress. To study the influence of plastic deformation before transformation, samples were plastically deformed in a temperature above Ms (martensite start temperature), the external force acting on the sample was removed and the material was allowed to transform into martensite by cooling in air. Pole figures were measured by EBSD (Electron Back-Scatter Diffraction) in both conditions and compared with calculated pole figures assuming Patel-Cohen model and Taylor-Bishop-Hill model. The orientation of the parent austenite was obtained either by reversing the austenite by heating at 650 ° C and by using the mathematically reconstructed austenite grains. Results showed that Patel-Cohen model were more suitable to elastic deformation while TaylorBishop-Hill model was more appropriated to plastic deformation.