High Cycle Fatigue Property of Al–Mg–Sc–Zr Alloy Fabricated by Laser Powder Bed Fusion

Abstract

Laser powder bed fusion (LPBF) of high‐strength Al–Mg–Sc–Zr alloy possesses great potential application in the aerospace industry. However, fatigue performance has become a very important issue in the safety and durability design of engineering structures. Herein, the high cycle fatigue property of LPBF‐fabricated Al–Mg–Sc–Zr alloy and its correlation with defects, microstructure, and precipitated phases are studied. The LPBF‐manufactured Al–Mg–Sc–Zr alloy appears heterogeneous structure composed of equiaxed grains at the molten pool boundary and columnar grains at the inner of the molten pool. After aging treatment (325 °C/4 h), the nanosized Al3Sc intragranular particles and Mn‐rich intergranular particles are precipitated, leading to more difficult movement of dislocations that favors the fatigue strength. The ultimate tensile strength of the samples after aging treatment is 507.05 MPa and corresponding 107 cycle fatigue strength (R = −1) is 106 MPa. The fracture morphology of the fatigue specimens shows that the fatigue cracks start from the surface defects with strong stress concentration, especially the lack of fusions, and then expand through the surplus part.