Effects of heat treatment on microstructures and properties of 7B04 aluminum alloy thick plates have been investigated by optical microscope and transmission electron microscope

tensile testing and electrical conductivity testing.The results show that the optimal solid solution is treated at 470 ℃ for 240 min.Maximum tensile strength of 621 MPa can be observed with lower electric conductivity only 18.3 MS/m

after aged at 120 ℃ for 22 h.Although the tensile strength of the alloy is decreased by 10%

1

2%

compared with that of T6 treated alloy

the electric conductivity is evidently improved by 21.3 MS/m after two-step T74 aging treatment.The high strength and high electric conductivity can be observed by RPA treatment

equivalent to T6 alloys in strength and to T4 alloy in electric conductivity.Amounts of fine disperoids are distributed into the RPA alloy with coarse and fully discontinuously distributed precipitation phase from the boundary.