Computational and Experimental Studies on the Effect Back Pressure on Twist Extrusion Process

Abstract

In the current study, aluminium 6063 alloy (AA6063) was successfully gain refined by twist extrusion (TE) technique. TE is a representative severe plastic deformation process to fabricate ultrafine-grained in bulk materials by repetitive passes. In order to investigate the influence of back pressure, a direct extrusion (DE) channel was embedded after the twist zone and the behavior of AA6063 was investigated and compared with and without this channel. Analyzing microstructural evolutions by scanning electron microscope and Vickers microhardness evaluations showed that, adding the DE channel increased the hardness distribution and a more homogenous structure was obtained. Finite element analysis was utilized to study the distribution of the equivalent plastic strain (PEEQ) numerically. According to the obtained results, with applying the TE process, strain increase was observed all over the sample surface, whereas modeling the DE channel after the twist zone caused a better homogeneity in the PEEQ distribution of the transverse cross-section. The PEEQ distribution during TE process can be correlated to the extent of grain refinement and the uniformity of ultrafine grains. This method seems to be very interesting and very promising for the future industrial application.