A3004-H112合金の機械的性質に及ぼす長時間加熱および焼なましの影響

抄録

The effects of aging and annealing conditions on the 0.2% proof stress of A3004-H112 aluminum alloy were investigated, in order to develop a method for evaluation of design strength taking account of the strength change caused by long-term service periods at elevated temperatures, in particular at approximately 200°C. It was confirmed that a decrease of 0.2% proof stress of the alloy during the aging and annealing was attributed largely to recovery of strain hardening initially existed in the as-extrusion state. It was also found that while content of supersaturated Mn varied depending on heat treatment conditions, its effect on strength was not dominant. It is suggested that in the case of aging treatment, holding at 250°C or 300°C for over 10³ h is necessary to obtain strength low enough at each holding temperature. Annealing treatments at 520°C for 10 h followed by a cooling rate of 0.5°C/h or smaller is also effective to reach sufficiently decreased 0.2% proof stress, by removing non-equilibrium strengthening factors such as strain hardening and supersaturated Mn solid solution. The aged and annealed A3004-H112 alloy specimens exhibited a similar 0.2% proof stress value when the conditions are selected as above.