Exrusion of magnesium-nickel alloys

Gravity cast billets in AZ91 alloy and two experimental alloys containing Nickel (AZ91+Ni), were directly extruded. Chemical composition of the Nickel containing alloys was designed such that it corresponded to a potential recycling quality of the AZ91 alloy. Extrusion trials were performed at 370⁰C, applying extrusion speed of 2.6 mmin-1 and reduction ratios 4:1 and 6:1. Effective strain distribution in the extruded rod as a function of the distance from the rod center was in the range 1.6 to 7, depending on the applied reduction ratio. These values were determined by FEM-analyze. Extrusion of the experimental alloys was not challenged by rather large, cubic shaped Nickel-based particles present in the microstructure of the experimental alloys. The extrusion process of these led to extruded rods with smooth surface without extruded failures of type hot cracks. No effect of Nickel on mechanical properties of AZ91 alloy was noticed either. Tensile test showed that echanical properties, Yield strength, Tensile strength and Elongation, were mainly driven by strain hardening and volume fraction of the brittle, precipitated betha-phase.