Twist channel multi-angular pressing (TCMAP) as a new SPD process: numerical and experimental study

Abstract

The paper proposes a new variation for the application of SPD methods. Suggested twisted channel multi-angular pressing (TCMAP) technology obtains the larger imposed strain more effectively while increasing homogeneity of the material. The number of passes needed to obtain the ultra-fine to nano-scale grains in bulk materials can be significantly reduced. Commercially pure Al (99.97%) was used for the experimental verification of the suggested process. The deformation behavior of the material during the process was also described using the numerical simulation based on FE analysis. It was proved that the geometric parameters of the die, as well as the used individual deformation sections sequence, can significantly affect the size and homogeneity of the imposed strain or stability of the plastic flow of material. Predicted value of imposed strain, after a single pass, reached approximately 2.8. It is obvious that during the TCMAP process no dead zones occurred in any of the channel deformation sections. Due to designed shape of channel are both ends of processed sample defined by higher imposed strain and only negligible shape changes. A comparison between the FEM and experimental results of the required loads and the homogeneity of the imposed strain distribution showed good agreement. The high homogeneity of the distribution of the deformation was confirmed by micro-hardness testing, whereas a relative growth of 97% was documented after the first pass. The grain size, determined after TCMAP pass, averaged out to be 2.4 μm.