Abstract
A new process of producing airplane frames was designed to reduce the costs. In this new process, 7475–W aluminum alloy sheets followed by reversion heat treatment (RHT) were used before roll formings instead of 7475–O ones. In this process, the hardness of the sheets after RHT should be below HV120, which was the limit hardness of roll forming. The most suitable condition of RHT, 453 K–40 s was recommended in this study. But the hardness after RHT wasn't reduced to the as-quenched condition. Furthermore, the hardness of the as-quenched specimen followed by RHT was raised to HV110 level. It was confirmed that copper addition reduces the precipitating temperature of η′ and η phase in the Al–Zn–Mg alloy. Then it was suggested that the dissolution of GP Zones and precipitation of η′ and η phase occurred simultaneously in 7475–W aluminum alloy sheet at the reversion heat treatment of 453 K–40 s.
