Aluminum alloy composition with improved elevated temperature mechanical properties

An aluminum alloy includes, in weight percent, 0.50-1.30% Si, 0.2-0.60% Fe, 0.15% max Cu, 0.5-0.90% Mn, 0.6-1.0% Mg, and 0.20% max Cr, the balance being aluminum and unavoidable impurities. The alloy may include excess Mg over the amount that can be occupied by Mg-Si precipitates. The alloy may be utilized as a matrix material for a composite that includes a filler material dispersed in the matrix material. One such composite may include boron carbide as a filler material, and the resultant composite may be used for neutron shielding applications.