Simultaneous Enhancement of Strength and Ductility in AM60 Tubes Using a Novel Approach of Modified Tube Cyclic Expansion Extrusion

The current study uses a modified tube cyclic expansion extrusion (M-TCEE) as a novel severe plastic deformation method to improve the microstructure and properties of AM60 magnesium alloy tubes. Employing a bulk rod-shaped punch in the M-TCEE process makes it feasible to apply greater pressing forces without worrying about the buckle of the punch, which is a problem encountered when using the traditional TCEE method that involves a hollow tubular punch. Consequently, this advancement allows for the manufacturing of tubes with increased length-to-diameter ratios. By undergoing the process, the initial large grains are refined and utilized to generate a bimodal grain structure that includes coarse cores encompassed by fine grains. The findings demonstrate that by performing the M-TCEE process, the yield strength increases by 78% compared to its initial value of 79 MPa, the ultimate tensile strength increases ~ 56% compared to its initial value of 147 MPa, and the ductility almost doubled (from ~ 2.7% to ~ 5.3%). Additionally, the microhardness rose from 56 HV to 82 HV. Also, the corrosion behavior of AM60 tubes is improved by the M-TCEE process, as indicated by the hydrogen evolution curves. Overall, the M-TCEE method has the potential to improve the microstructural, mechanical, and corrosion characteristics of AM60 tubular samples.