Enhanced fracture toughness in an annealed Al-Cu-Mg alloy by increasing Goss/Brass texture ratio

• Goss-grains are still able to facilitate crack deflection in the toughness testing.
• Brass-, S- and Copper-grains show little resistance to crack propagation in the toughness testing.
• The high Goss/Brass ratio is responsible for the enhanced fracture toughness.
• A new method to accurately evaluate the twist and tilt angle has been proposed.

The effect of grain orientation on fracture toughness of an annealed Al-Cu-Mg alloy has been investigated by using XRD, SEM, OM and EBSD in the present work. A new method has been presented to accurately evaluate the twist and tilt angle of grain boundaries. EBSD detection results indicate Goss-grains in the annealed Al-Cu-Mg alloy, having a great twist angle or tilt angle component boundary with the neighboring grains, are still able to facilitate crack deflection under the condition of uniaxial tensile stress creating no crack closure, as compared with cyclic loading condition with crack closure in fatigue testing. Goss-grains, thereby effectively retard fracture crack propagation. In contrast, the fast-propagating crack is easy to penetrate through Brass-, S- and Copper-grains. Apparently, the high Goss/Brass volume fraction ratio is responsible for the enhanced fracture toughness in the Al-Cu-Mg alloy plate annealed at 385 °C for 4 h.

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