Thermodynamic Investigation of Alkali-Metal-Induced High Temperature Embrittlement in Al-Li Alloys

✍ Scribed by S. Zhang; Q. Han; Z.-K. Liu

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 186 KB
• Volume: 9
• Category: Article
• ISSN: 1438-1656
• DOI: 10.1002/adem.200700183

✦ Synopsis

Aluminum-lithium alloys are very important structural materials and widely used in aircraft and aerospace industries due to their contributions to higher fuel efficiency through weight reduction. Compared with other Al alloys, Al-Li alloys have a lower density at the equivalent strength levels. The addition of 1 wt. % Li to an Al alloy results in a 6 % increase in the elastic modulus and a 3 % decrease in density. However, they have a variable short-transverse fracture toughness in rolled, extruded and forged forms due to trace amounts of alkali-metal impurities like Na and K. Alkali-metal impurities are introduced into Al-Li alloys through feedback and pickup from refractories. Commercial grades Al-Li alloys usually contain 3-10 wt. ppm alkali-metal impurities inevitably.

Payne and Eynon first mentioned Na-induced embrittlement in Al-Li alloys for the Na content over 50 ppm. Vaynblat et al. found that the fracture toughness drops 16 % in COMMUNICATIONS