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摘要
The relationships between electrical conductivity, hardness and microstructure of 7050 alloy during isothermal quenching at 180~250℃following solid-solution treatment were investigated. Results show that in the initial stage of isothermal quenching at 180℃and 200℃, the electrical conductivity of isothermal specimens is lower than that of the specimen directly water quenched after solid-solution treatment, and with the increase of isothermal time, the hardness of isothermal specimens in natural aging temper increases first and then decreases. When isothermally quenching at 180℃for 7680 s, GPΙzones and η'phases form in matrix. When isothermally quenching at 200℃for 1920 s, GPΙand GPΙΙzones form in matrix. And when isothermally quenching at 250℃for 1920 s, η'and S phases form in matrix. The formation of strengthening phases during isothermal quenching is the main reason for the increase in the hardness of specimens under natural aging temper. When 7050 alloy plate is isothermally quenched at 200℃for 960 s after solid-solution treatment, its T6 temper hardness is only 3.4% lower than that of the directly water quenched plates and its conductivity increases by 9.2%, which is close to the properties of RRA treated plates with a regression regime of 180℃for 1920 s. Therefore, after solid-solution treatment, isothermal quenching at 200℃for 960 s as a pre-treatment process will give 7050 alloy plates excellent comprehensive properties.
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