Abstract: The effects of progressive solution treatment on microstructure and mechanical properties of 7A04 aluminum alloy were investigated. Results indicate that after solutionized under condition of 470℃, 5min+485℃, 9min and subsequent aging process of 140℃, 6h+150℃, 1h, σ_b， σ_0.2 and δ₅ of 7A04 alloy reach 544.6MPa， 498.8MPa and 11.1% respectively. Metallography observation indicates that the grain size after short-time progressive solution treatment（470℃, 5min+485℃, 3-9min） is smaller than that after single-stage solution at 485℃. SEM observation indicates that the progressively solutionized sample in tension test behaves as typical dimpled fracture. X-ray diffraction analysis indicates that after progressive solution under the condition of 470℃, 5min+485℃, 9min, MgZn₂ as main strengthening phase is totally dissolved except a small amount of Al₂Cu. EDAX analysis indicates that the main undissolved phases are inclusions rich in Fe and Cu. Because the grain size of the sample progressively solutionized at 470℃, 5min+485℃, 9min is smaller than that of single-step solutionized at 485℃, the supersaturation degree of the progressivly solutionized sample reaches that of the sample single-step solutionized at 500℃, 20min, and obtains the highest mechanical properties after subsequent aging, which is equal to those got by traditional solution process.

Key words: high strength aluminum alloy; progressive solution; microstructure; property