Enhanced mechanical properties of magnesium alloy seamless tube by three-roll rotary piercing with severe plastic deformation

•Mg alloy seamless tubes were successfully fabricated by three-roll rotary piercing process.•The grains of MASTs were refined to 12.5% of the original grain size by TRPP.•The UTS and elongation were all improved significantly after TRPP.•The enhanced elongation was attributed to GBS and the easier activation of non-basal slips. Three-roll rotary piercing process (TRPP) with severe plastic deformation was conducted to fabricate magnesium alloy seamless tubes with high mechanical properties. After TRPP, the grains are refined to 12.5% of the original grain size and microstructure became more homogeneous due to accumulated strains. The tensile strength was improved due to grain refinement, a large number of spherical nanoparticles dispersed in the matrix and generation of new mixed texture. The elongation increased from 11% for the as-extruded billet to about 20% for tube. The enhanced elongation was attributed to grain boundary sliding and the easier activation of non-basal slips contributed by remarkable grain refinement.