Aluminum Alloys for ALS Cryogenic Tanks: Comparative Measurements of Cryogenic Mechanical Properties of Al-Li Alloys and Alloy 2219
Final rept. Aug 1989-Mar 1990
NATIONAL INST OF STANDARDS AND TECHNOLOGY BOULDER CO
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Tensile and plane-strain fracture toughness properties were obtained at cryogenic temperatures to compare the Al-Li alloys 8090, 2090, and WL049 and alloy 2219 in various tempers and specimen orientations. The strongest alloy at very low temperatures is WL049-T851, which is about 10 stronger than 2090-T81. Both alloys are considerably stronger than 2219-T87. Alloy 2090-T81 is tougher in the in-plane orientations about 50 than WL049-T851 at low temperatures the higher in-plane toughness is attributed to the presence of less constituent particles and the tendency to crack out-of-plane or delaminate at low temperatures. This delamination tends to divide the moving crack, thus separating it into smaller regions where plan stress rather than plane strain conditions are conducive to increased toughness. Thus, a dichotomy reduced toughness in the through-thickness or out-of-plane orientations leads to increased toughness in the in-plane orientations. In service, a leak in the tank is considered failure, and a leak will be caused by a crack in the panels of the tankage growing through the panel thickness. To measure the resistance to crack growth under these conditions, surface-flawed panel tests are recommended.
- Metallurgy and Metallography