Mapping the Plastic Flow in the High Strain Linear Flow Splitting ProcessThursday (29.09.2016) 12:30 - 12:45 Part of:
Due to their superior properties, ultrafine grained (UFG) microstructures have become of large interest in recent years. The new cold forming process linear flow splitting (LFS) is used to generate branched profiles from plain sheet metal. During the process, a strongly elongated pancake UFG microstructure evolves at the flange surface. Perpendicular to the flange surface there is a microstructural gradient from UFG at the upper surface to a work hardened microstructure with micron sized grains at the lower flange surface. An aspect that is not well understood so far is the material flow in the LFS forming zone leading to the described microstructure. However, due to the high plastic strains occurring in the LFS process the plastic flow is not easily accessible.
To understand the material flow in the LFS process a novel technique for mapping the material flow based on tracers was developed. This approach uses a tracer gradient that is introduced into the material by diffusion. After the deformation the gradient is mapped by EDS and TOF-SIMS to quantify the material flow. The present work shows the results of mapping a Ni gradient imposed on HSLA steel LFS profiles as well as on undeformed sheet metal. By comparing the tracer location before and after further splitting steps, the plastic flow path in the process was investigated.