Effect of microstructure on outer surface roughening of magnesium alloy tubes in die-less mandrel drawing

The crystal orientation and outer surface roughening of magnesium alloy tubes were evaluated to clarify the effect of the mandrel on the microstructure and outer surface roughness in die-less mandrel drawing. Locally heated ZM21 tubes with an outer diameter of 6.0 mm and an inner diameter of 3.8 mm were drawn with and without a mandrel. The outer surface roughness and crystal orientation were evaluated in the same measurement area. The results indicated that the outer surface becomes rougher in the die-less mandrel drawing than in die-less drawing for a given outer circumferential strain. The outer surface roughness developed when there was large difference in the pyramidal slip system Schmid factor. Therefore, the slip deformation of the pyramidal slip system seems to be mainly responsible for the outer surface roughening in the die-less mandrel drawing. Furthermore, the crystal grain with the {2 1 over bar 1 over bar 0} crystal plane vertical to the normal direction of outer surface had a larger Schmid factor than the other crystal grains. The large number of crystal grains with the {2 1 over bar 1 over bar 0} crystal plane in the die-less mandrel drawing is one of the reasons that the outer surface roughness develops more in the die-less mandrel drawing than in die-less drawing for a given outer circumferential strain. These results will contribute significantly to the development of fabrication process of the microtube with high surface quality, which prevents rapid corrosion of biomedical applications. (c) 2022 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University

Automated summary

The crystal orientation and outer surface roughness of magnesium alloy tubes were evaluated to investigate the effect of the mandrel in die-less mandrel drawing. The results showed that the outer surface became rougher in the die-less mandrel drawing compared to die-less drawing. The roughness development was attributed to the difference in the pyramidal slip system Schmid factor. Furthermore, crystal grains with the {2 1 over bar 1 over bar 0} crystal plane had a larger Schmid factor and contributed to the increased roughness in the die-less mandrel drawing. These findings are significant for the development of fabrication processes that produce microtubes with high surface quality.