Processability and characterization of A20X aluminum alloy fabricated by laser powder bed fusion

The processing window for laser powder bed fusion (LPBF) of A20X aluminum alloy was determined to increase the build rate and reduce the fabrication cost for this material. The influence of hatch spacing, laser scan speed, and powder layer thickness on the microstructure and mechanical properties were also systematically investigated. Over a wide processing window (40-115 J/mm3 energy density), near fully dense and crack-free components were achieved. In all cases, the as-built microstructure consisted of an aluminum matrix with TiB2 particles and Al2Cu precipitates, where volume fraction and size of both TiB2 and Al2Cu phases were found to be independent of the LPBF process parameters. A fine equiaxed grain structure with a random crystallographic orientation was observed in the vertical section (XZ-plane) of the as-built samples. This led to an isotropic elastic modulus, ultimate tensile strength, and total elongation. The yield strength, however, was found to be anisotropic, exhibiting a 16 % difference for different orientations. The average grain size decreased 54 % due to increased scan speed and reduced powder layer thickness. This resulted in a remarkable improvement in the alloy micro-hardness value from 108 HV to 124 HV, where the experimental data obeyed the Hall-Petch relationship.

Automated summary

The LPBF processing window for A20X aluminum alloy was determined to optimize build rate and reduce fabrication cost. The influence of hatch spacing, laser scan speed, and powder layer thickness on microstructure and mechanical properties were investigated. Near fully dense and crack-free components were achieved within a wide energy density range. The as-built microstructure consisted of an aluminum matrix with TiB2 particles and Al2Cu precipitates, and the volume fraction and size of these phases were independent of process parameters. The grain structure in the vertical section showed isotropic properties, while the yield strength exhibited anisotropy.