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

Physical and mechanical properties of aluminum alloy 2024 containing lithiu m additions were investigated. Lithim (2, 3, and 4 wt%) was added to the al loy of 2024. Melting was carried out in an induction furnace under argon ga s 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 qu enched in water at room temperature. They were then aged. For the purposes of comparison, some of the specimens were melted under argon gases, but cas ting was done without vacuum. All the specimens were subjected to tension a nd hardness tests. In this study, an increase of 6% in the modulus of elast icity 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 f ound to be better than those cast without vacuum. Whatever the lithium perc ent in the alloys, all the mechanical properties reached their maximum leve l in 1 week of natural aging; for artificial aging, maximum levels were rea ched at 120 degreesC in 24 h, at 160 degreesC in 16 h, at 190 degreesC in 1 2 h, and 200 degreesC in 2 h. By increasing the lithium percent, the specif ic 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 re served.