Effect of Two-stage Aging on China 7050 Aluminum Plate

China 7050 aluminum plate belongs to the Al-Zn-Mg-Cu alloy, featuring low density, high strength, good workability, spalling corrosion resistance, and good stress corrosion cracking (SCC) resistance. It is often used in aerospace and modern lightweight vehicles, tooling,etc.

The solution treatment is carried out in an air furnace, the solution temperature is controlled at (743±5) K, the solution time is 70 min. It adopts water quenching. The electric heating blast drying oven is used for drying, and the temperature accuracy is controlled at ±5 K.

Under the two-stage aging system, the primary aging is aging for 8 hours at 383 and 393 K, respectively; the secondary aging is long-term aging at 423 and 433 K, and the aging time is controlled within 0 to 140 h.

The bimodal phenomenon exists in 7050 two-stage aging. The aging hardness and strength curve first increase and then decrease with the extension of the two-stage aging time. The elongation basically showed a downward trend with the progress of aging, but it slightly increased at each peak position and showed a certain peak.

After two-stage aging treatment under different conditions, the fracture toughness of 7050 aluminum alloy is different. When the heat treatment system is 743 K×70 min+393 K×55 h (single-stage), the KIc value is 32.2 MPa·m1/2; when 743 K×70 min+393 K×8 h+423 K×17 h, KIc The value is 30.1 MPa·m1/2; when 743 K×70 min+393 K×8 h+423 K×33 h, the KIc value is 30.3 MPa·m1/2; 743 K×70 min+393 K×8 h+ At 423 K×45 h, the KIc value was 38.5 MPa·m1/2; at 723 K×70 min+393 K×8 h+423 K×57 h, the KIc value was 28.7 MPa·m1/2.

Among them, the fracture toughness of the alloy reached the maximum value of 38.5 MPa∙m1/2 at 45 h. When the single-stage aging peak is 55 h, although the strength and hardness are higher, the fracture toughness is lower.

Compared with single-stage aging, the aging time of the two-stage aging is shortened, the heat treatment efficiency is improved, and the cost is reduced. Haomei Aluminum is a professional supplier of 7050 aircraft aluminum sheet. Welcome to leave message below to inquire it.