Texture and Microstructure Evolution at the Metal-Vapour Interface During Transformation Annealing in a Mn and Al Alloyed Ultra Low Carbon Steel

Abstract

This paper investigates the evolution of texture and microstructure at the metal-vapour interface during transformation annealing in vacuum. Interrupted annealing experiments were carried out on cold rolled Mn, Al and Si alloyed ultra low carbon steels. The textures were characterized by X-ray diffraction and SEMEBSD techniques. The results show the variation in the surface texture components obtained after BCC recrystallisation and double α−γ−α transformation annealing. The recrystallisation texture consists mainly of a //ND fibre, while the transformation texture at the surface exhibits a //ND fibre in combination with components of the //ND fibre. It was revealed that the latter specific surface texture was present in a monolayer of outer surface grains which were in direct contact with the vapour atmosphere. This observed phenomenon could be explained by considering the role of surface energy anisotropy occurring during phase transformation annealing.