ADC12合金ダイカストの機械的特性に及ぼす組織構造の影響

抄録

In recent years, weight saving of car body is required in automobile industry to solve the issue of global warming. Aluminum alloy is one of the light materials to replace steel. ADC12, which is Al-Si_10.4-Cu_1.74 alloy (mass%), is widely used for the die casting alloy. However, ADC12 alloy has a problem due to the low strength compared to that for the steel. In this research, the microstructure of ADC12 alloy die casting was controlled by two new methods to increase the mechanical properties: (i) Precipitation strengthening because of CuAl2. In this process, aging treatment at low temperature (175 °C) was applied to the die casting samples; (ii) Microstructure refinement and spheroidizing by the addition of appropriate amount of Na. In general, it is difficult and dangerous to use Na caused by active material. In this study, an attempt was made to employ NaHCO3. From the examination of microstructural characteristics on the mechanical properties, high hardness was obtained for ADC12 alloy die casting after heating at 175 °C for 3 h. Furthermore, the α-Al + Si eutectic structure of ADC12 alloy die casting became fine and spherical with 0.1% Na. With these microstructure control, the Vickers hardness improved by about 15% and the tensile strength increased by about 40%.