Plastic Forming of AZ91 Alloy Using the KOBO Method

Abstract

The desirability of using the KOBO extrusion process for AZ91 magnesium alloy preceding its further plastic processing has been experimentally verified. Importantly, during the conducted experiments, heat treatment (e.g., homogenization) was applied either before or after direct KOBO extrusion, which if used might have affected the properties of the alloy. The products of the cold KOBO process take the form of tapes with different cross sections. They were pressed (deep drawing), or, alternatively, subjected to conventional indirect extrusion in order to acquire the desired spatial geometry of the product. Due to the need for relatively wide strips, a variant of the KOBO extrusion with lateral outflow was used, since the press structure, providing reversibly oscillating die, strongly limited the cross sections of directly extruded products. The research procedure, involving plastic deformation with cyclic changes of the deformation path, allowed to obtain results indicating new potential properties of metallic materials crucial for their applicability.