Physical and mechanical properties of cast under vacuum aluminum alloy 2024 containing lithium additions

Physical and mechanical properties of aluminum alloy 2024 containing lithium additions were investigated. Lithim (2, 3, and 4 wt%) was added to the alloy of 2024. Melting was carried out in an induction furnace under argon gas protection; casting was performed under vacuum. The cast material was hot extruded to produce tension test rods. To obtain the maximum strength and hardness, the specimens were solution heat treated at 495 degreesC, then quenched in water at room temperature. They were then aged. For the purposes of comparison, some of the specimens were melted under argon gases, but casting was done without vacuum. All the specimens were subjected to tension and hardness tests. In this study, an increase of 6% in the modulus of elasticity and 3% decrease in the density were obtained for 1% lithium added to the alloy. The mechanical properties of the alloys cast under vacuum were found to be better than those cast without vacuum. Whatever the lithium percent in the alloys, all the mechanical properties reached their maximum level in 1 week of natural aging; for artificial aging, maximum levels were reached at 120 degreesC in 24 h, at 160 degreesC in 16 h, at 190 degreesC in 12 h, and 200 degreesC in 2 h. By increasing the lithium percent, the specific elastic modulus (E/rho) of the alloy increased rapidly but the specific strength (sigma/rho) remained constant. Thus, aluminum lithium alloys that are difficult to manufacture by known methods can be manufactured safely by the vacuum metallurgy method. (C) 2000 Elsevier Science Ltd. All rights reserved.