The effects of the two-step solution treatment on the microstructure of aluminum alloy 7050 hot rolled sheet were investigated.The results show that

after two-stage solution treatment

a large number of coarse phases in hot-rolled sheets are redissolved.When the first-step solution temperature is increased from 450 ℃ to 470℃

the content change of coarse Sphase in the alloy can be ignored.With the secondary solution temperature increase

the Sphase content is decreased and the recrystallization fraction is increased.The effect of secondary solution temperature on recrystallization fraction of microstructures is the greater than that of holding time.The microstructures of thick plates at different thicknesses are vaned to some extent after solution treatment.Under different two-stage solid solution processes

the coarse S phase in the surface and at H/2 of the thick plate is completely dissolved

however the recrystallization fraction at H/2 of the thick plate is the higher than that of ones at surface and H/4.