不連続繊維強化アルミニウム合金複合材料ビレットの押出し性

抄録

The extrudability of β-SiC whisker or Al₂O₃ discontinuous fiber reinforced aluminum alloy composite billets was investigated in terms of the extrusion shear stress, the whisker or fiber length in extruded bars and the extrusion speed. The extrusion shear stress of composite billets increased with the amounts of whisker or fiber and the shear stress of the matrix alloys. The extrusion shear stress of the composite billets exceeded the limit for the normal extrusion of aluminum alloy billets. The increased extrusion temperature resulted in the decreased extrusion shear stress, but this caused the defect of tearing on the extrusions. Thus, the extrusion condition for composite billets was found to be limited. The break down of whisker or fiber in extruded bars was not improved by decreasing the shearing force during extrusion using conical dies or increased extrusion temperatures. The extrusion speed for composite billets increased up-to more than double of the maximum extrusion speed attained with steel dies by using Si₃N₄ ceramic die or capping thin matrix alloy layer on the leading top of composite billet. These methods were also effective to reduce the extrusion force for composite billets. Thus, these unique methods improved the extrudability of discontinuous fiber reinforced aluminum alloy composite billets.