Structure and Properties of Rapidly Solidified 2000 Series Al-Li Alloys

摘要

The literature appears convincing that of the Al-Li alloys, Al-Cu-Li provides stronger alloys than does Al-Mg-Li. Yet, such earlier studies were based on ingot technology where segregation problems could conceivably have worsened actual comparisons. Further, the phase diagrams for these two ternary systems are poorly known, especially if significant additions of Mn, Cd, Cr, Ti, Zr and other elements are made. In fact the Al-Cu-Mg-Li quaternary based on the 2024 alloy gave some rather excellent combinations of strength and toughness when the alloys were made from rapidly solidified (RS) particulates. Continuing alloy development, structure refinement, and property assessments, based on RS technology, are the basis of this study. Both 2020 and 2024 base alloys are being prepared by RS powder technology (ultrasonic gas atomization with quench rates of ten to the 4th power to ten to the 5th power K/s); lithium contents from about 1 to 3 weight percent are being studied at several different ratios of Cu to Li. Phase identification studies are being planned but only preliminary data are available. Mechanical properties (smooth bar tension tests) appear excellent for the Al-Cu-Li alloys, significantly better than for the 2024 base alloy. Notch toughness tests are still a problem even though improvements are being made. (Author)