Microstructure and Fatigue Properties of Al2024-RAM2 Aluminum Alloy Obtained by Laser Powder Bed Fusion

Abstract

The wrought 2024 aluminum alloy is an established aluminum alloy with copper as the primary alloying element. Due to its high strength and fatigue resistance, it is widely used for aircraft primary structures. Development of the AM counterpart of this high-strength alloy starting from gas atomized powder has been challenged by its tendency to hot tearing during solidification thus compromising mechanical properties. Recently, the innovation by Elementum 3D made the 2024 alloy compatible with the Laser Powder Bed Fusion technology (L-PBF). The key is a patented production process of reactive additive manufacturing (RAM), which utilizes exothermic chemical reactions to synthesize product materials during the additive process to improve printability while achieving mechanical properties comparable to those of a conventionally produced alloy.This contribution examines the Al2024-RAM2 alloy recently qualified for industrial production by the service company BEAM IT (Fornovo Taro, Italy). The powder was processed in a SLM 280 HL Twin system (SLM Solutions GmbH, DE) to fabricate specimens for fatigue testing which then underwent a solution-plus-aging heat treatment (T6). Specimens oriented in three different directions with respect to the build direction were left in the as-built surface state and used for the characterization of microstructure and surface quality. Fatigue data obtained under high cycle fatigue loading conditions are presented and discussed in terms of directional effect and surface integrity (as-built vs. polished surfaces).