| 摘要 |
<p>This invention relates to aluminium alloys containing lithium which are particularly suitable for aerospace construction and have been found to have improved damage tolerance in regard to their fatigue crack deviation behaviour. The method of producing a damage tolerant sheet of lithium-containing aluminium alloy having reduced susceptibility to fatigue crack deviation comprising providing a sheet of the said alloy with an unaged structure, ageing the sheet at a temperature and for a time near to, at, or over the peak aged condition for that alloy based upon its proof stress properties sufficient to increase precipitation of at least one planar slip blocking phase, heating the sheet to an elevated temperature higher than its ageing temperature and holding the sheet at that temperature for a time sufficient to facilitate significant dissolution of the δ' phase precipitates therein without significant dissolution of any planar slip blocking phase, and then cooling the sheet. Preferably the alloy has a composition within that specified for one of the registered alloys 8090, 8091, 2090 and 2091. The preferred post-ageing (reversion) conditions for 8090 are 4 minutes at 230 °C.</p> |
