Metallurgical Gradients in Structural Materials: Potential and Challenges in Creating Artificial Segregations in Medium Manganese Steel via Roll-Bonding

Abstract

Segregation of alloying elements in metallic structural materials is often considered detrimental, as it results in local inhomogeneities of microstructure and properties. However, controlled levels of segregation may be utilized to adapt and improve the bulk property profile as a composite structure of metallurgical gradients. Roll-bonding appears as an attractive technique to study and optimize the effects of segregations in a systematic manner. Here, the feasibility of creating artificial manganese segregation bands of ±5 wt%, in a medium manganese steel of the base composition Fe–0.1C–7Mn (wt%) in an alternating sequence, is demonstrated. After intercritical annealing at 650 °C for 6 h, the Fe–0.1C–7Mn layer consists of ≈17 vol% ultrafine-grained austenite in a ferritic matrix. The Fe–0.1C–12Mn layer contains a higher amount of austenite, while the Fe–0.1C–2Mn layer shows a fully ferritic microstructure. The differences in mechanical behavior between the roll-bonded and reference material emphasize the role of manganese segregations in controlling the local stability of austenite under different stress states. Moreover, the corrosion investigations in 0.1 m H2SO4 reveal the preferential dissolution of adjacent high manganese containing layers. Challenges regarding the roll-bonding methodology for creating model materials, especially the role of layer interfaces, are outlined and discussed.