With the growing environmental concerns surrounding transportation machines, magnesium alloy, which has an excellent specific strength, good vibration damping and a high electromagnetic shielding capability, is increasingly being used in automobile body parts in order to reduce the carbon emissions and to increase the energy efficiency through a reduction in the mass. However, forming techniques with magnesium alloy at room temperature pose considerable difficulty owing to its strong plastic anisotropy of tension and compression. In this study, a control arm, which is a complex-shaped part in the suspension system of a vehicle, was warm forged with Mg–8 mass % Al–0.5 mass % Zn (AZ80) alloy to reduce the mass. To validate the applicability of the magnesium alloy control arm in the automobile, its microstructure and its mechanical properties were analysed.

This paper demonstrates the effect of the extrusion ratio on the mechanical properties of the as-forged Mg-8Al-0.5Zn alloy. Three extruded Mg bars with the extrusion ratio of 9:1, 16:1, and 25:1 are prepared in the same extrusion condition, which are applied to the warm forging test to obtain the different microstructure with respect to the degree of extrusion effect in Mg alloys. The extrusion ratio over 16:1 has little effect on the mechanical properties of the as-extruded bars since the average grain size and amount of precipitates hardly change. The forgeability of the highly extruded bar is improved around flange area while the mechanical properties are slightly enhanced. The rod-type and particle-type precipitates tend to be favored in the as-forged microstructure with the extrusion ratio over 16:1.