Grain Refinement Efficiency of Multi-Axial Incremental Forging and Shearing: A Crystal Plasticity Analysis

Severe plastic deformation is a technical method to produce functional material with special properties such as high strength and specific physical properties. Selection of an efficient severe plastic deformation for grain refinement is a challenging field of study and using a modeling technique to predict the refinement efficiency has gained a lot of attentions. A comparative study was carried out on the grain refinement ability of two severe plastic deformation techniques. Accordingly, beta-tin samples were processed for almost the same strain level by the equal channel angular extrusion (ECAE) and the newly developed multi-axial incremental forging and shearing (MAIFS). Optical microscope and tensile tests were used to investigate the microstructure and mechanical properties. It was found that the MAIFS process is more efficient in grain refinement than ECAE by help of crystal plasticity analysis and experimental observation. This was ascribed to the more activated slip systems in MAIFS than ECAE and activation of secondary modes of deformation in MAIFS. The conclusion was supported by the finer grains that was observed in the sample processed by MAIFS and compared with grain size of the sample processed by ECAE. Finally, these observations were related to materials flow for beta-Tin during tensile test.