Metallurgical Mechanisms Controlling Mechanical Properties of Aluminium Alloy 2219 Produced by Electron Beam Freeform Fabrication

Abstract

The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties have been demonstrated for electron beam deposited aluminum and titanium alloys that are comparable to wrought products, although the microstructures of the deposits exhibit features more typical of cast material. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. In the current study, mechanical properties and resulting microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Material performance was evaluated based on tensile properties and results were compared with properties of Al 2219 wrought products. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains, typically with interior dendritic structures, which were described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processingmicrostructure- property correlations.

Elevated temperature characterization of electron beam freeform fabricated Ti–6Al–4V and dispersion strengthened Ti–8Al–1Er

“…Additional beads are deposited incrementally until the entire 3D shape has been created. The end product is a near-net shape part that can, with proper processing parameters, be fully dense and have mechanical properties similar or equivalent to wrought or forged material [6][7][8][9][10]. If successfully utilized, this process could decrease manufacturing costs through reduction of part count, elimination of machining steps, and reduced raw material requirements.…”

Mechanical properties of Ti-6Al-4V specimens produced by shaped metal deposition

“…Especially for complex shapes and small quantities, the fabrication of net shape components by additive layer manufacturing can reduce the costs by omitting extensive machining and production of scrap. Several techniques are considered, including direct laser fabrication [1][2][3][4][5][6][7][8][9][10], electron beam freeform fabrication [11][12][13] and tungsten inert gas welding [14][15][16]. The technique used in this paper is shaped metal deposition (SMD), which is a net shape tungsten inert gas welding process patented by Rolls-Royce.…”

Electron Beam Freeform Fabrication in the Space Environment

“…10 and 11. This is a typical microstructure observed in EBF 3 deposits 6 . Both deposits exhibit typical cast aluminum solidification microstructure, consisting of columnar grains initiating at the bottom of the molten pool and growing perpendicular to the substrate surface .…”