Tube Cyclic Extrusion-Compression (TCEC) as a novel severe plastic deformation method for cylindrical tubes

A severe plastic deformation (SPD) method entitled Tube Cyclic Extrusion-Compression (TCEC) is proposed. Cylindrical tubes are deformed through TCEC to large strains without dimensional and geometrical changes. In the TCEC method, tubular specimen is constrained in a space with constant volume and is deformed between mandrel and chamber in which a neck zone was devised. TCEC was applied to commercial AZ91 magnesium alloy leading to substantial grain refinement even after single cycle of TCEC. Mean grain size of 800 nm was achieved after two cycles of TCEC. Microhardness of the initial tube increased from 65 Hv to 92 Hv after two processing cycles of TCEC. Moreover, hardness assessment along tube thickness demonstrates good homogeneity of hardness distribution. After two processing cycles of TCEC, yield and ultimate strengths were increased by 3 and 2.7 times compared to those in as-cast condition. The elongation to failure was also increased from initial value of 1.6% to about 9%. In order to further investigate the accumulated strains, the TCEC process was also numerically modeled by FE code of ABAQUS/Explicit. The TCEC method seems a promising SPD process for industrial applications.