Improvement of formability of Mg-2.2Gd-0.4Zr alloy by forming multi-type textures through the transverse gradient extrusion process

Abstract

Mg-2.2Gd-0.4Zr sheets were prepared using transverse gradient extrusion (TGE) technology to improve their formability. The effects of different TGE processes (inclination angles of the die are 15°, 30°, 37°, 45° and 49°) on the microstructure, texture, mechanical properties, and formability of extruded sheets were researched. Furthermore, the flow behaviors of Mg-2.2Gd-0.4Zr sheets during extrusion were analyzed by the finite element simulation method. For comparison, Mg-2.2Gd-0.4Zr sheets were processed by conventional extrusion (CE) process. Results showed that the texture of TGE sheets was effectively altered. With the increase of the TGE dies tilt angle, the deviation of the basal pole in the center region of the extruded sheet towards the extrusion direction (ED) increased, while in the 1/4 edge region the basal pole deviated towards the transverse direction (TD) along the ED. The multi-type textures formed in TGE sheets are mainly attributed to the extra flow velocity along the TD and the flow gradient along the ED during extrusion. High elongation of 45.6% and low yield stress of 98.9 MPa are obtained for TGE-45 sheets. In addition, the Erichsen value (IE) of the TGE-45 sheet is 5.46 mm, which is about 47% higher than the 3.72 mm of the CE Mg-2.2Gd-0.4Zr sheet. The improved formability is due to the effective coordination of multi-directional strains during the Erichsen test for the TGE sheets.

Keywords

• Transverse gradient extrusion
• Microstructure
• Multi-type textures
• Mechanical properties
• Formability