Abstract A method is described of thermally treating the 7,000 series aluminum alloys that have been subjected to a solution heat treatment at a high temperature and then to an ageing treatment at a lower temperature, thereby hardening the alloy but likewise producing therein a susceptibility to stress-corrosion cracking. The novel method comprises the steps of (1) subjecting the alloy to a retrogression heat treatment for a short period of time at a temperature above the age-hardening temperature of the alloy but below the solution heat treatment temperature, and (2) subsequently subjecting the alloy to a re-ageing heat treatment for a substantially longer period of time at the age-hardening temperature of the alloy. This method substantially reduces the susceptibility of the alloy to stress-corrosion cracking while retaining its original strength.
Inventors
👤 B Cina
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-31 15:26
CPC Classifications
C; C22; C22F; C22F1/00; C22F1/04; C22F1/053
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
145 words
A METHOD OF SUBSTANTIALLY REDUCING THE SUSCEPTIBILITY TO STRESS-CORROSION CRACKING OF THE 7,000 SERIES ALUMINUM ALLOYS CONTAINING ZINC, MAGNESIUM, AND COPPER, WHILE STILL RETAINING THEIR ORIGINAL MECHANICAL STRENGTH, WHILE ALLOYS HAVE BEEN SUBJECTED TO A SOLUTION HEAT TREATMENT AT A HIGH TEMPERATURE AND THEN TO AN AGING TREATMENT AT A LOWER TEMPERATURE THEREBY HARDENING THE ALLOY BUT LIKEWISE PRODUCING THEREIN A SUSCEPTIBILITY TO STRESS-CORROSION CRACKING, COMPRISING THE STEPS OF: A. SUBJECTING THE ALLOY TO A RETROGRESSION HEAT TREATMENT FOR A FEW SECONDS TO A FEW MINUTES AT A TEMPERATURE OF FROM 200*C TO 260*C, WHICH TEMPERATURE IS ABOVE THE AGEHARDENING TEMPERATURE OF THE ALLOY BUT BELOW THE SOLUTION HEAT TREATMENT TEMPERATURE; AND B. SUBSEQUENTLY SUBJECTING THE ALLOY OT A RE-AGING HEAT TREATMENT AT A TEMPERATURE FROM 115*C TO 125*C FOR A SUBSTANTIALLY LONGER PERIOD OF TIME THAN IN STEP (A) UP TO A SEVERAL DAYS.
Claim 2
Independent Claim
145 words
A METHOD OF SUBSTANTIALLY REDUCING THE SUSCEPTIBILITY TO STRESS-CORROSION CRACKING OF THE 7,000 SERIES ALUMINUM ALLOYS CONTAINING ZINC, MAGNESIUM, AND COPPER, WHILE STILL RETAINING THEIR ORIGINAL MECHANICAL STRENGTH, WHILE ALLOYS HAVE BEEN SUBJECTED TO A SOLUTION HEAT TREATMENT AT A HIGH TEMPERATURE AND THEN TO AN AGING TREATMENT AT A LOWER TEMPERATURE THEREBY HARDENING THE ALLOY BUT LIKEWISE PRODUCING THEREIN A SUSCEPTIBILITY TO STRESS-CORROSION CRACKING, COMPRISING THE STEPS OF: A. SUBJECTING THE ALLOY TO A RETROGRESSION HEAT TREATMENT FOR A FEW SECONDS TO A FEW MINUTES AT A TEMPERATURE OF FROM 200*C TO 260*C, WHICH TEMPERATURE IS ABOVE THE AGEHARDENING TEMPERATURE OF THE ALLOY BUT BELOW THE SOLUTION HEAT TREATMENT TEMPERATURE; AND B. SUBSEQUENTLY SUBJECTING THE ALLOY OT A RE-AGING HEAT TREATMENT AT A TEMPERATURE FROM 115*C TO 125*C FOR A SUBSTANTIALLY LONGER PERIOD OF TIME THAN IN STEP (A) UP TO A SEVERAL DAYS.
Claim 3
Dependent Claim
14 words
The method as defined in claim 1, wherein said alloy is aluminum alloy 7075.