There is a strong desire among automobile manufacturers to reduce the fuel consumption and greenhouse gas emissions of their current vehicles. Reducing the overall weight of a vehicle represents the most practical opportunity to reduce fuel consumption. Replacing the current steel sheet structures with lightweight alternatives, such as aluminum, offers an excellent solution. Much of the attention in North America has been focused on copper-containing Al-Mg-Si aluminum alloys (6xxx series), such as AA6111. These alloys offer an excellent combination of good formability and precipitation-strengthening ability.<p> In this study, the effect of solute concentration on the strength and strain aging behavior of a proprietary Al-Mg-Si-(Cu) alloy was evaluated. The experimental design used was a 26 full factorial design, with the primary factors being the solute concentrations of magnesium, silicon, and copper, as well as the effects of applied strain (cold work), and natural and artificial aging heat treatments (e.g., a simulated paint bake process). The primary investigative techniques employed included tensile testing, microhardness measurements, and optical metallography.<p> The results show that cold work and artificial aging produce the most substantial strengthening in the alloys. The occurrence of natural aging prior to forming and artificial aging reduced strengthening. The highest strength levels in the naturally aged and paint baked condition, which most closely resembles what is found in industry, were achieved at a combination of low magnesium levels (i.e., 0.5 wt.%) and high silicon and copper levels (i.e., 0.9 and 0.3 wt.%, respectively).

There is a strong desire among automobile manufacturers to reduce the fuel consumption and greenhouse gas emissions of their current vehicles. Reducing the overall weight of a vehicle represents the most practical opportunity to reduce fuel consumption. Replacing the current steel sheet structures with lightweight alternatives, such as aluminum, offers an excellent solution. Much of the attention in North America has been focused on copper-containing Al-Mg-Si aluminum alloys (6xxx series), such as AA6111. These alloys offer an excellent combination of good formability and precipitation-strengthening ability.<p> In this study, the effect of solute concentration on the strength and strain aging behavior of a proprietary Al-Mg-Si-(Cu) alloy was evaluated. The experimental design used was a 26 full factorial design, with the primary factors being the solute concentrations of magnesium, silicon, and copper, as well as the effects of applied strain (cold work), and natural and artificial aging heat treatments (e.g., a simulated paint bake process). The primary investigative techniques employed included tensile testing, microhardness measurements, and optical metallography.<p> The results show that cold work and artificial aging produce the most substantial strengthening in the alloys. The occurrence of natural aging prior to forming and artificial aging reduced strengthening. The highest strength levels in the naturally aged and paint baked condition, which most closely resembles what is found in industry, were achieved at a combination of low magnesium levels (i.e., 0.5 wt.%) and high silicon and copper levels (i.e., 0.9 and 0.3 wt.%, respectively).