Effect of truncated cone billet on single-step back extrusion forming process of magnesium alloy wheel

Magnesium (Mg) alloy wheels formed by single-step back extrusion currently faced with the phenomenon of coarse grains at the spokes, insufficient recrystallization, and easy cracking at the upper rim, which seriously affects the service performance and yield of the wheel. Based on the actual production process conditions of Mg alloy wheels, this paper simplifies the numerical model of the wheel back extrusion and proposes a truncated cone billet for wheel back extrusion by analyzing the streamline in the current wheel forming process. Research indicates that during the forming process of the cylindrical billet, the upper edge material of the billet fills the rim, the lower edge material fills the lower rim, and the lower core material forms the wheel spokes. Compared with cylindrical billets, truncated cone billets can increase the effective strain, dynamic recrystallize volume fraction and refine grains at the spokes and the lower rim. Simultaneously, the truncated cone billets can improve the fluidity at the rim, making the rim filling easier and reducing the cracking tendency at the upper rim. The truncated cone billet is of great significance to the back extrusion forming of Mg alloy wheels. (c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This study simplifies the numerical model of back extrusion and proposes a truncated cone billet to improve the issues faced by magnesium alloy wheels formed by single-step back extrusion. The truncated cone billet increases effective strain, dynamic recrystallization volume fraction, and refines grains at the spokes and lower rim. It also improves the fluidity at the rim, making rim filling easier and reducing cracking at the upper rim. The use of truncated cone billets is of great significance for the back extrusion forming of magnesium alloy wheels.