The Role of Hydrogen in the Stress Corrosion Failure of High Strength Al-Zn-Mg Alloys.
Abstract
Previous studies have been shown that high strength A1-Zn-Mg based alloys suffer environment assisted cracking. In the present work, room temperature constant strain rate (.0001/s - .000001/s) and constant load tensile tests on A1 6% Zn 3% Mg and copper and chromium containing variants were extended to specimens pre-exposed to a steam environment at 120 C and to specimens tested in air, distilled water and salt solution. The embrittlement increased at lower strain rates, higher water content, and in the presence of chloride ions. In all cases, atomic hydrogen absorbed into the grain boundaries and the grain matrix causes grain boundary decohesion and cleavage. The ability to trap atomic hydrogen as H2 bubbles improves the embrittlement resistance. It is believed that the addition of copper to the alloy increases the hydrogen trapping efficiency, hence embrittlement resistance whereas in the chromium containing alloy, the oxide is probably modified to inhibit hydrogen entry. Originator supplied keywords include: Aqueous environments, cleavage, constant strain rate test, corrosion wedging effect, crack arrest, crack branching, dead load test, discontinuous crack growth (microscopic and macroscopic), dissolution, ductility ratio, grain hydrogen embrittlement, hydrogen permeation, life time ratio, pre-exposure steam environment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 06, 1984
- Accession Number
- ADA150891
Entities
People
- H. M. Flower
- M. L. Yuen
Organizations
- Imperial College London