Evaluation of the effects of variations in chemical composition on the quality of Al-Si-Mg, Al-Cu, and Al-Zn-Mg cast aluminum alloys

The effect of slight variations in chemical composition on the quality of cast aluminum alloys from three different major alloy systems was evaluated. For the evaluation of the alloy quality, an index Q_D adjusted to damage tolerance requirements that are currently involved for the design of advanced lightweight structures is used. The quality index Q_D accounts for tensile strength and ductility as well as for material failure through yielding or fracture. For this investigation, experimental results obtained for variations in chemical composition of the alloy systems Al-Si-Mg, Al-Cu, and Al-Zn-Mg were exploited. In total, castings from 37 different batches from 10 aluminum alloys, varying in chemical composition, were evaluated. Quality characterization and alloy quality ranking were made by evaluating results of 512 tensile tests using the index Q_D as well as, for comparison, the quality index Q, which is currently used by the industry. The results obtained involving the index Q_D seem to be more realistic, from the viewpoint of damage tolerance design requirements.