Suppression of Macroscopic Defects through the Control of Friction between Workpiece and Dies in a Forged Magnesium Alloy Part with Ribs

Abstract

Superplastic magnesium alloy sheets were closed-die forged into an experimental part with ribs, which are asymmetrical elements to the plane of the forging. A macroscopic surface defect, which was formed by extrusion-type flow, was observed opposite to the rib during forging under improper lubrication conditions. However, the formation of the defect could be successfully suppressed by changing the frictional conditions of the workpiece/dies interface. Analysis of the rib forging using a finite controlled volume method simulation suggested that the suppression of the extrusion-type defect is associated with a change in velocity field distribution of the deforming material.