Densification, Microstructure, and Mechanical Properties of Additively Manufactured 2124 Al–Cu Alloy by Selective Laser Melting

Abstract

Owing to its high specific strength and low density, Al–Cu alloys have been extensively used in aerospace for lightweight components. Additive manufacturing techniques such as selective laser melting, which offers geometric freedom, is suitable for topology-optimized designs. In this study, the effect of processing parameters on the densification, microstructure, and mechanical properties of additively manufactured Al–Cu alloy 2124 by selective laser melting was investigated. Parameters such as laser power, scanning speed, hatch spacing, and use of a support were studied. The results revealed that a grille support with a hollow structure played a resistant role in the transfer of heat to the base plate, thus reducing the temperature gradient and lessening cracks in the building part. Smaller hatch spacing was beneficial for the achievement of a higher relative density and strength due to track re-melting and liquid phase backflow, which could fill cracks and pores during the building process. An ultimate tensile strength as high as 300 MPa of the vertically built sample was obtained at optimized processing parameters, while the elongation was relatively limited. Moreover, columnar grains were found to be responsible for the anisotropy of the mechanical properties of the as-printed 2124 alloy.

Ongoing Challenges of Laser-Based Powder Bed Fusion Processing of Al Alloys and Potential Solutions from the Literature—A Review

“…According to the Kruth et al’s simulations [ 99 ], the chessboard scanning strategy with a 90° rotation could be an optimal solution to induce an isotropic stress tensor advantageous for residual stresses in the component, avoiding long scan vector lengths and uniformly oriented scan vectors. An important role in reducing residual stress and avoiding delamination formation is played by the VED [ 100 ]. For example, reducing scan speed values, Levkulich et al [ 101 ] achieved an enhanced densification behaviour during the PBF-LB\M process and a reduced level of residual stresses.…”

Towards an alloy design strategy by tuning liquid local ordering: What solidification of an Al-alloy designed for laser powder bed fusion teaches us

“…Thermodynamic solidification calculations were conducted using Thermo-Calc with the database dedicated to Al-alloys (TCAL6 version 6.0). Calculations were run using the Scheil-Gulliver model by considering only phases that have been identified experimentally in a previous study: Al 9 , the characteristic size of tortuous pores is about 500 nm, which is very small compared to the ten-micron-sized spherical ones. According to the 3D nano-imaging experiment (see 2D cross-sections), which allows the revealing of the microstructure and defects, the tortuous pores are exclusively found in the interdendritic regions.…”

Additive Manufacturing of Aluminum‐Based Metal Matrix Composites—A Review

“…There are plenty of PBF-L alloys having a cellular structure where the dislocations are accumulated along the cellular structure boundary, such as PBF-L 306L, PBF-L Al12Si, PBF-L AlMg10Si, PBF-L CCM alloys, and PBF-L AgCu alloys. [125][126][127][128][129][130][131][132] In such cases, the length scale of the cellular structures (s) controls the overall strengthening level. Then the dislocation strengthening due to dislocation cell walls can be given as [133] Δσ…”