AUXILIARY HEAT TREATMENT FOR ALUMINIUM-LITHIUM ALLOYS

摘要

Artificially aged aluminium-lithium alloys are given an auxiliary heat treatment at or after completion of ageing to improve short-transverse properties, particularly fracture toughness. The auxiliary heat treatment comprises heating the material steadily to a reversion temperature above the ageing temperature by at least 20 DEG C but not higher than 250 DEG C, retaining the material briefly at temperature then cooling to room temperature. Typically the treatment involves heating to a reversion temperature in the range 190-230 DEG C with a hold at this temperature of around 5 minutes. Boosted properties decay with extended exposure to temperatures of 60 DEG C and above but may be restored by reimposition of the auxiliary heat treatment.