Directed energy deposition of Al 5xxx alloy using Laser Engineered Net Shaping (LENS®)

TLDR

Porosity origins in the deposited material are discussed. The study presents directed energy deposition of wrought‑like Al 5xxx AlMg alloy using Laser Engineered Net Shaping (LENS®). Density was quantified by μ‑CT and Archimedes methods, while mechanical properties were assessed through tensile tests with DIC, fractography, and pulse‑echo ultrasonic NDT. The DED process produced Al 5754‑like material with 99.26 % relative density, equiaxed and columnar grains averaging 36 μm, and mechanical properties meeting international standards for wrought Al 5754 in its annealed condition.

Abstract

Here, we present directed energy deposition (DED) of wrought-like Al 5xxx AlMg alloy by Laser Engineered Net Shaping (LENS®). A transition from an Al 5083 gas atomized powder feedstock to Al 5754 characteristics of the as-deposited material due to selective evaporation of Mg was observed. Density values obtained by X-ray micro-computed tomography (μ-CT) were compared to those obtained by the Archimedes method. The latter indicated a relative density as high as 99.26%. Possible origins of porosity are discussed. The as-deposited material was comprised of both equiaxed and columnar grains with no preferred crystallographic orientation and mean grain size of 36 μm. The Young's modulus, yield stress, ultimate tensile strength, fracture strain, Poisson's ratio, and total ultimate strain energy (toughness) were determined by uniaxial tensile tests combined with digital image correlation (DIC). Fractography complemented the mechanical testing. A pulse-echo ultrasonic non-destructive test was used to obtain more accurate values of the Young's and shear moduli and to adjust the value of the yield strength accordingly. The measured mechanical properties meet the requirements of international standards for wrought Al 5754 in its annealed condition.