Four-step thermal aging method for improving environmentally assisted cracking resistance of 7xxx series aluminium alloys

Abstract

Four-step thermal aging method for improving environmentally assisted cracking resistance of 7xxx series aluminium alloys. The thermal aging is carried out by treating the alloys at a temperature of 120 to 130 oC for 0.3 to 0.5 h, water quenching the alloys to a temperature of 25 to 27 oC and further treating the alloys at a temperature of 80 to 95 oC for 100 to 120 h and at a temperature of 120 to 130 oC for 20 to 24 h and at a temperature of 155 to 160 oC for 1 to 5 h and air cooling the alloys to room temperature, sequentially.

1 - 3 . (canceled) 
     
     
         4 . A thermal aging method for improving environmentally assisted cracking resistance of 7xxx series aluminum alloys, comprising, sequentially:
 solutionizing and thermally aging a 7xxx series aluminum alloy, the thermal aging comprising:   treating the alloy at a temperature of 120 to 130 oC for 0.3 to 0.5 hours;   water quenching the alloy to a temperature of 25 to 27 oC;   treating the alloy at a temperature of 80 to 95 oC for 100 to 120 hours;   treating the alloy at a temperature of 120 to 130 oC for 20 to 24 hours;   treating the alloy at a temperature of 155 to 160 oC for 1 to 5 hours; and   air cooling the alloy to room temperature.   
     
     
         5 . The method of  claim 4 , the thermal aging steps comprising:
 treating said alloy at a temperature of 130 oC for 0.5 hours;   water quenching said alloy to 27° C.; and   further treating said alloy at a temperature of 85 oC for 120 hours, at a temperature of 130 oC for 24 hours, and at a temperature of 157 oC for 2.5 hours.   
     
     
         6 . The method as claimed in  claim 4 , said alloy comprising any of AA 7010, AA 7050, or AA 7085. 
     
     
         7 . The method as claimed in  claim 5 , said alloy comprising any of AA 7010, AA 7050, or AA 7085.