Effect of hydrogen in molten aluminum on the growth of micro-porosity and mechanical properties of squeeze cast material

For automobile or other machine parts, the squeeze cast aluminum alloys have been used because of its lower defects compared to the conventional die cast aluminum alloys. The effect of the hydrogen in molten aluminum alloys on the growth of the micro-porosity and mechanical properties of the squeeze cast aluminum alloys were investigated. After controlling the hydrogen content, the molten alloy was cast into a cavity with 90 MPa. In the case of hydrogen-added material, the number density of the micro-porosities increased during solid-solution treatment regardless of the type of the alloys, AC4CH, AC8A or ADC 12. On the other hand, porosity was scarcely found in the degased materials. Therefore, the formation of porosity is likely to be caused by the release of the supersaturated hydrogen to the α-aluminum phase during heat treatment. As to the as-cast AC4CH material, the fracture elongation was increased with addition of hydrogen. However the tensile strength of the as-cast or T6 material was little affected by the hydrogen content.