Hydrogen Assisted Fatigue Cracking of High Strength Aluminum Alloys.
Abstract
High cycle tension-tension fatigue tests have been performed on a 7075-T6 alloy in air, in 0.5N NaCl, pre-corroded in 0.5N NaCl, re-heat-treated and tested in air. Additionally fatigue tests were performed on a high purity analogue alloy, (Al-5.5Zn 2.5Mg-1.5Cu) in air, in 0.5N NaCl and in NaCl with applied cathodic currents (hydrogen charged). Corrosion fatigue of the high-purity alloy resulted in intergranular crack initiation with a shift to transgranular cracking as the crack propagated. High charging currents and high cyclic stresses tended to reduce the relative amount of intergranular cracking. Transgranular fatigue fracture surfaces differing from those observed in air tests in that they were highly faceted (crystallographic) and exhibited cleavage-type markings. These results indicate that corrosion fatigue of high-strength aluminum alloys is a hydrogen embrittlement process with hydrogen being produced by corrosion of the alloy. Transgranular cracking occurs when high cyclic stresses induce mobile dislocations which cause hydrogen migration into the grains in fatigue-generated slip bands.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1975
- Accession Number
- ADA014477
Entities
People
- D. J. Duquette
- E. F. Smith Iii
- R. Jacko
Organizations
- Rensselaer Polytechnic Institute