マグネシウム -重希土類元素合金の鍛造性および鍛造材の時効特性と引張特性 Forgeability of Mg-heavy rare earth metal alloys and aging characteristics and tensile properties of their forged materials
The forgeability into a cup shape, a basic shape for a engine piston, was evaluated on the heat and corrosion resistant Mg-heavy rare earth metal alloys. Furthermore, aging characteristics and tensile properties of the die-forged specimens were also investigated. Mg–10%Gd–3%Nd–Zr (GN103K), Mg–10%Dy–3%Nd–Zr (DN103K) and Mg–10%Gd–3%Y–Zr (GY103K) alloys are formed into a cup shape by die-forging under conditions of the specimen temperature of 500°C, mold temperature higher than 300°C and forging rate lower than 0.3 m/s. Coarse equilibrium precipitates are observed to be already existing in GN103K and DN103K alloys after die-forging. Hardness increase by aging is, therefore, small in GN103K alloy and little in DN103K alloy. On the other hand, GY103K alloy exhibits only fine recrystalized grains without coarse precipitates, resulting in marked hardness increase by aging. The age hardening of the alloy is caused by both the fine β''–phase with the D0<sub>19</sub> structure and fine/β'–phase with the bco structure. At temperatures between 200 and 250°C, the proof stress and tensile strength of the specimens prepared from the bottom and side of the forged GY103K alloy in a cup shape are higher than those of the conventional WE54A heat resistant magnesium alloy.
軽金属 47(5), 261-266, 1997-05-30
The Japan Institute of Light Metals