A method of forming a heat treatable aluminum alloy, the method comprising: (a) forming a melt consisting of: 3.0 to 6.0 weight percent magnesium; 0.5 to 3.0 weight percent lithium; at least one first element selected from the group of 0.1 to 0.5 weight percent scandium, 0.1 to 6.0 weight percent erbium, 0.1 to 10.0 weight percent thulium, 0.1 to about 15.0 weight percent ytterbium, and 0.1 to 12.0 weight percent lutetium; at least one second element selected from the group of 0.1 to 4.0 weight percent gadolinium, 0.1 to 4.0 weight percent yttrium, 0.05 to 1.0 weight percent zirconium, 0.05 to 2.0 weight percent titanium, 0.1 to 2.0 weight percent hafnium, and 0.05 to 1.0 weight percent niobium; optionally further at least one of 0.001 weight percent to 0.1 weight percent sodium, 0.001 weight percent to 0.1 weight percent calcium, 0.001 weight percent to 0.1 weight percent strontium, 0.001 weight percent to 0.1 weight percent antimony, 0.001 weight percent to 0.1 weight percent barium, and 0.001 weight percent to 0.1 weight percent phosphorus; no more than 0.1 weight percent iron, 0.1 weight percent chromium, 0.1 weight percent manganese, 0.1 weight percent vanadium, 0.1 weight percent cobalt, and 0.1 weight percent nickel; and the balance being aluminum and unavoidable impurities; (b) solidifying the melt to form a solid body; and (c) heat treating the solid body; wherein the solidifying comprises a rapid solidification process in which the cooling rate is greater than about 10 3 °C/second; and wherein the heat treating comprises: solution heat treatment at 800°F (426°C) to 1100°F (593°C) for thirty minutes to four hours; quenching; and aging at 200°F (93°C) to 600°F (315°C) for two to forty-eight hours. (a) forming a melt consisting of: 3.0 to 6.0 weight percent magnesium; 0.5 to 3.0 weight percent lithium; at least one first element selected from the group of 0.1 to 0.5 weight percent scandium, 0.1 to 6.0 weight percent erbium, 0.1 to 10.0 weight percent thulium, 0.1 to about 15.0 weight percent ytterbium, and 0.1 to 12.0 weight percent lutetium; at least one second element selected from the group of 0.1 to 4.0 weight percent gadolinium, 0.1 to 4.0 weight percent yttrium, 0.05 to 1.0 weight percent zirconium, 0.05 to 2.0 weight percent titanium, 0.1 to 2.0 weight percent hafnium, and 0.05 to 1.0 weight percent niobium; optionally further at least one of 0.001 weight percent to 0.1 weight percent sodium, 0.001 weight percent to 0.1 weight percent calcium, 0.001 weight percent to 0.1 weight percent strontium, 0.001 weight percent to 0.1 weight percent antimony, 0.001 weight percent to 0.1 weight percent barium, and 0.001 weight percent to 0.1 weight percent phosphorus; no more than 0.1 weight percent iron, 0.1 weight percent chromium, 0.1 weight percent manganese, 0.1 weight percent vanadium, 0.1 weight percent cobalt, and 0.1 weight percent nickel; and the balance being aluminum and unavoidable impurities; 3.0 to 6.0 weight percent magnesium; 0.5 to 3.0 weight percent lithium; at least one first element selected from the group of 0.1 to 0.5 weight percent scandium, 0.1 to 6.0 weight percent erbium, 0.1 to 10.0 weight percent thulium, 0.1 to about 15.0 weight percent ytterbium, and 0.1 to 12.0 weight percent lutetium; at least one second element selected from the group of 0.1 to 4.0 weight percent gadolinium, 0.1 to 4.0 weight percent yttrium, 0.05 to 1.0 weight percent zirconium, 0.05 to 2.0 weight percent titanium, 0.1 to 2.0 weight percent hafnium, and 0.05 to 1.0 weight percent niobium; optionally further at least one of 0.001 weight percent to 0.1 weight percent sodium, 0.001 weight percent to 0.1 weight percent calcium, 0.001 weight percent to 0.1 weight percent strontium, 0.001 weight percent to 0.1 weight percent antimony, 0.001 weight percent to 0.1 weight percent barium, and 0.001 weight percent to 0.1 weight percent phosphorus; no more than 0.1 weight percent iron, 0.1 weight percent chromium, 0.1 weight percent manganese, 0.1 weight percent vanadium, 0.1 weight percent cobalt, and 0.1 weight percent nickel; and the balance being aluminum and unavoidable impurities; (b) solidifying the melt to form a solid body; and (c) heat treating the solid body; wherein the solidifying comprises a rapid solidification process in which the cooling rate is greater than about 10 3 °C/second; and wherein the heat treating comprises: solution heat treatment at 800°F (426°C) to 1100°F (593°C) for thirty minutes to four hours; quenching; and aging at 200°F (93°C) to 600°F (315°C) for two to forty-eight hours. solution heat treatment at 800°F (426°C) to 1100°F (593°C) for thirty minutes to four hours; quenching; and aging at 200°F (93°C) to 600°F (315°C) for two to forty-eight hours.