圧縮ねじり加工したAZ61マグネシウム合金の微視組織に及ぼす回転回数の影響

Abstract

Grain refinement and texture control in magnesium alloys are an effective way of improving mechanical properties. We have investigated the possibility of microstructure control of metal materials by compressive torsion processing. This process can apply a large strain to a cylindrical work piece by simultaneous compressive and torsional loadings without changing the shape of the work piece. It is expected that not only grain refinement but also texture control can be achieved. In the present work, we applied this process to the microstructure improvement of extruded AZ61 magnesium alloy. The effect of rotation number on microstructure control was investigated. The microstructure of each specimen after processing was analyzed quantitatively and the distribution of grain size was determined. In addition, texture was measured by X-ray diffraction analysis. Grains of several micrometers were observed in the specimens under all conditions. The grains in the specimen processed with a large rotation number were refined homogeneously over the cylindrical work piece. Most basal planes, which were initially oriented parallel to the cylindrical axis, were distributed nearly perpendicular to the axis, the compressive direction, after processing.