Microstructural Compatibility of an Al-Li-Cu-Mg-Zr Alloy Exposed to Corrosive Environments
Abstract
This investigation evaluated the influence of microstructure on fracture characteristics and general corrosion resistance of a quaternary Al-2. 8Li-1.3Cu-0.7Mg alloy 8090 in the peak-aged condition in environments of wide range of aggressiveness. In the aging condition studied, fracture was predominantly low energy intergranular and intersubgranular separation. The fracture process was observed to be governed by a complex interplay of several concurrent and mutually competitive factors involving intrinsic microstructural features, the matrix deformation characteristics and grain boundary failure. Corrosion rate was established through weight loss measurements using ASTM G31 coupons. Immersion test results indicate that weight loss occurred in both acidic and basic solutions. Corrosion rates decreased with time of immersion in solution. Solution pH changed during the test period. Weight loss measurements, and optical and scanning electron microscopy observations indicate that coupons of the quaternary alloy begin to corrode rapidly during the initial hours of immersion in the solution followed by a period of uniform corrosion in which pitting dominates. In highly hostile environments (aqueous solutions) the alloy appears to undergo enhanced corrosion along grain boundaries. This is also evident after prolonged immersion in less hostile environments. Pitting occurred at the second-phase particles dispersed in the matrix, and at the grain boundary precipitate particles. (edc)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1987
- Accession Number
- ADA215540
Entities
People
- T. S. Srivatsan