Decisive influence of critical process parameters on the microstructure and tensile properties of friction stir back extruded magnesium alloy tubes

Friction Stir Back Extrusion (FSBE) is evolving as a novel extrusion process for producing high strength ultrafine-grained tubes from a range of metallic alloys. This investigation focuses on developing a high-fidelity experimental methodology to control the critical process parameters of the FSBE process for manufacturing high strength ZE41 magnesium alloy tubes. The crucial parameters of FSBE required to manufacture highly reliable ZE41 tubes were determined with solid evidence obtained through a wide range of thorough experimental trials on ZE41 magnesium round rods. The metallurgical characterisation was performed at key regions across the tubes obtained using the ideal process conditions to understand the influence of FSBE process parameters on the microstructural formation. Mechanical properties of the tubes were evaluated and found that the tubes produced at optimum conditions have achieved high tensile and hoop strengths. The microstructure-mechanical property correlation confirmed that the FSBE process driven with the controlled process parameters enable to produce defect-free high strength ZE41 magnesium tubes with a significant enhancement in grain refinement.