Structural integrity of additively manufactured aluminum alloys: Effects of build orientation on microstructure, porosity, and fatigue behavior

The use of aluminum (Al) alloys for additive manufacturing (AM) has recently gained significant attention, specifically in the aerospace industry. This has been resulting in introducing new high strength Al alloys that are more compatible with the AM processes. However, it is critical to investigate the structural integrity of these newly developed Al alloys prior to being deployed in safety-critical load-bearing applications. This study investigates and compares the microstructure, porosity, and fatigue behavior of five different contemporary Al alloys fabricated via a laser beam powder bed fusion (LB-PBF) AM process. Vertically and horizontally built specimens out of AlSi10Mg, Scalmalloy, QuesTek Al, AD1, and AlF357 are fabricated to capture any effects of build orientation on the structural integrity of these alloys. Despite the variation in micro-/defect-structure of vertical and horizontal specimens, no significant build orientation dependency is observed on fatigue behavior of AlSi10Mg, Scalmalloy, and AD1 alloys. However, AlF357 and QuesTek Al show some anisotropic behavior in the high cycle fatigue regime. Among the LB-PBF Al alloys investigated, Scalmalloy and AD1 are found to have the highest fatigue resistance ascribed to their superfine microstructure.