Abstract
The present study addressed the effect of heat treatment process on microstructure of an AlSi10Mg lattice structure with a body-centered cubic unit cell manufactured via laser powder bed fusion (LPBF). The as-manufactured lattice specimen exhibited a unique cellular structure composing of primary α-Al phases bounded by α-Al/Si eutectic microstructure. A gradient microstructure (continuous microstructural changes) was found in the node and strut portions composed of the lattice specimen. The microstructure appears more equiaxed and coarser with approaching the bottom surface of both portions. The continuous microstructural changes contributed to a variation in hardness measured at different locations in the as-manufactured lattice specimen. Si particles finely precipitate in the primary α-Al phases, and eutectic Si particle coarsening occurs at an elevated temperature of 300 °C. The microstructural coarsening is more pronounced at a higher temperature. A number of significantly coarsened Si particles and a stable Fe-containing intermetallic phase (β-AlFeSi) were observed at all locations in 530 °C solution-treated specimen. The homogenous microstructure results in a constant hardness value independent of the location in the lattice specimen. These results provide new insights to control the compressive properties of the AlSi10Mg lattice structure manufactured via LPBF by subsequent heat treatment processes.
Highlights
IntroductionPorous metals exhibit various unique physical properties, including low volumetric density, low thermal conductivity, good permeability, high specific stiffness, and high impact energy absorption [1]
Porous metals exhibit various unique physical properties, including low volumetric density, low thermal conductivity, good permeability, high specific stiffness, and high impact energy absorption [1].In particular, the absorption energy of lightweight porous aluminum (Al) under compression has been studied by Koza et al [2] for potential applications in the crumple zones of automobiles
The melt pools were observed in the specimen annealed at 300 ◦ C as well (Figure 2b,e), whereas their morphologies were not observed in optical micrographs of 530 ◦ C solution treated specimen (Figure 2c,f)
Summary
Porous metals exhibit various unique physical properties, including low volumetric density, low thermal conductivity, good permeability, high specific stiffness, and high impact energy absorption [1]. The absorption energy of lightweight porous aluminum (Al) under compression has been studied by Koza et al [2] for potential applications in the crumple zones of automobiles. The stable plateau stress and large plateau-end strain are required to achieve high impact energy absorption. To improve the energy absorption capability, it is essential to control the structural factors of the porosity, pore shape, pore size, and pore distribution [3]. Additive manufacturing (AM) techniques enable to manufacture complicated shapes from computer-aided design (CAD) models [4,5]. Laser powder bed fusion (LPBF) is a class of AM techniques using a laser beam to melt and fuse layers of metal powder particles forming various metal products with complex shapes, which cannot be manufactured by conventional techniques [6]
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