Additive Manufacturing of AlSi10Mg Alloy Using Direct Energy Deposition: Microstructure and Hardness Characterization

Abstract

This paper aims to study the manufacturing of the AlSi10Mg alloy with direct energy deposition (DED) process. Following fabrication, the macro-and microstructural evolution of the as-processed specimens was initially investigated using optical microscopy and scanning electron microscopy. Columnar dendritic structure was the dominant solidification feature of the deposit; nevertheless, detailed microstructural analysis revealed cellular morphology near the substrate and equiaxed dendrites at the top end of the deposit. Moreover, the microstructural morphology in the melt pool boundary of the deposit differed from the one in the core of the layers. The remaining porosity of the deposit was evaluated by Archimedes' principle and by image analysis of the polished surface. Crystallographic texture in the deposit was also assessed using electron backscatter diffraction and x-ray diffraction analysis. The dendrites were unidirectionally oriented at an angle of *80°to the substrate. EPMA line scans were performed to evaluate the compositional variation and elemental segregation in different locations. Eventually, microhardness (HV) tests were conducted in order to study the hardness gradient in the as-DED-processed specimen along the deposition direction. The presented results, which exhibited a deposit with an almost defect free structure, indicate that the DED process can suitable for the deposition of Al-Si-based alloys with a highly consolidated structure.

The Effect of Stress Relief on the Mechanical and Fatigue Properties of Additively Manufactured AlSi10Mg Parts

“…Figure 2a showed cellular and dendritic growth, which was also observed in the optical microstructure. Wu et al [22] attributed these cellular growths as long cells that are formed as a result of cooling conditions in place of dendrites. The dark region seen in Figure 2b,c was drastically eradicated in Figure 2e,f, where more silicon and aluminum were visible.…”

“…The dark region seen in Figure 2b,c was drastically eradicated in Figure 2e,f, where more silicon and aluminum were visible. These dark regions, according to Wu et al [22] and Mathe et al [6], are aluminum grains that also contain Al-Si eutectic, which is difficult to distinguish from cell boundaries because of the disappearance of diffraction data. Figure 2d has developed roughness on its surface that looks "pimple" like as compared to Figure 2a before stress relief.…”

“…In these samples, the columnar and equiaxed grains were observed before stress relief. These have been proposed to be formed directly by solidification that takes places as cellular dendrites as a consequence of rapid cooling with little information for the mechanism of formation [22,24]. In the optical microstructure, it was stated as silicon segregation to the grain boundaries as a result of rapid cooling [19].…”

“…Wu et al [22] stated that the reason SLM processed AlSi10Mg is optimum in strength is because the larger aluminum regions contains silicon particles, which are surrounded by the thick eutectic boundaries that prevents dislocation movement inside the aluminum grains. In these pictures, it is observed that the dark lines seen before stress relieved are removed.…”

Influence of Process Parameters and Deposition Strategy on Laser Metal Deposition of 316L Powder

“…Some approaches are based on modelling and measuring the melt pool dimensions, and on the understanding of their overlapping, others select the process parameters based on bulk components' porosity, geometrical accuracy, or microstructure and mechanical properties [5,[11][12][13][14]. Recently LMD 2 of 11 has been successfully used to process different alloys such as AlSi10Mg, Ti6Al4V, IN625 and 316L SS, showing several promising results [15][16][17][18]. In particular, some studies focused on the mechanical and microstructural characterisation of steel samples built by LMD and on the influence of process parameters on its mechanical behaviour.…”