Abstract
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A large-scaled 2219 aluminum alloy ingot with size of ��1380 mm��3700 mm was manufactured by ultrasonic assisted casting technology. And multidirectional hot forging, horse frame reaming, ring rolling and thermo-mechanical treatment were used to manufacture the ignot into a transition ring with diameter of ��5000 mm for rocket tank. It is found from the investigation of the microstructure of Al2Cu and mechanical properties of the ingot and ring that the eutectic microstructure near the center of the ingot is bridged to form a network morphology with an area fraction of 8.25%. The content of these eutectic microstructure decreases gradually from the center to the edge of the ingot, and the continuity is decreased. Then the coarse-dense Al2Cu phase is broken and dissolved after the ring forming process, the content of Al2Cu phase in the matrix is significantly reduced. Al2Cu phase aggregates near the inner diameter of the ring with average size of 5-12 ��m and area fraction of 1.02%. Dense Al2Cu phase tends to cause stress concentration and act as preferential nucleation sites for micro-cracks. Consequently, the strength and elongation near the inner diameter of the ring are lower, but both meet the design requirements. Besides, the Al2Cu phase is dispersed near the outer diameter of the ring with area fraction of 0.49%. A large number of ��' strengthening phases are precipitated evenly in the matrix, and the strength and elongation of the material meet the design requirements.