Inhomogeneity and fatigue properties of ultra-wide 7B50-T7751 aluminum alloy thick plate

Abstract

The microstructure and performance homogeneity of 80 mm thick ultra-wide 7B50-T7751 plate with different widths and thicknesses were studied by means of mechanical testing machine and scanning electron microscope, and the fatigue properties were compared and discussed with 7050-T7451 plate. The results show that the ultra-wide 7B50-T7751 plate has excellent mechanical properties. In L and LT directions, the tensile yield strength of 1/2 thickness reaches up to 568 MPa and 545 MPa, and the tensile strength reaches up to 612 MPa and 591 MPa, the compressive yield strength reaches up to 575 MPa and 587 MPa, the fracture toughness in L-T direction and T-L direction reaches 30.16 MPa·m1/2 and 26.47 MPa·m1/2, respectively. The ultra-wide thick plate exhibits certain anisotropy at different width positions, the performance homogeneity in LT direction tends to be better than in L direction. Performance at different width positions with 1/4 thickness shows little difference, while the performance at the edge of 1/2 thickness is better than that of the center. No obvious texture exhibits at 1/4 thickness, however, the main textures at the center of 1/2 thickness are S texture and Brass texture, and the main textures at the edge are R texture, S texture and Brass texture. When the stress ratio is 0.06, the T-L anti-fatigue crack growth rate performance of ultra-wide 7B50-T7751 thick plate is better than 7050-T7451 plate with the same thickness. The fatigue limit of LT smooth sample (Kt=1) is about 7.6% inferior than that of 7050-T7451 plate, while the fatigue limit of notch sample (Kt=3) is about 3.7% higher.

Keywords

• 7b50-t7751
• ultra-wide thick plate
• inhomogeneity
• microstructure
• fatigue property