Evolution of Microstructure, Texture and Corrosion Properties of Additively Manufactured AlSi10Mg Alloy Subjected to Equal Channel Angular Pressing (ECAP)

Abstract

In the selective laser melting process (SLM), the region irradiated by the laser beam is melted and quickly solidified, forming solidification lines (laser scan tracks) with symmetrical shapes. Because of the unique (rapid) crystallization conditions, the subgrain structures, typically observed inside these solidification lines, could also have variable geometric symmetrical patterns, e.g., cellular, pentagonal, or hexagonal cellular. The existence of such distinctive microstructures in SLM-made alloys has a significant impact on their superior mechanical and corrosion properties. Thus, any modification of this symmetrical microstructure (due to post-processing) can degrade or improve the properties of SLM-fabricated alloys. This study presents the experimental results on the effects of heat treatment and ECAP on microstructure modification and corrosion behavior of SLM-fabricated AlSi10Mg alloy. Light microscopy, scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and X-ray diffraction (XRD) were used for microstructural analysis. The corrosion properties of the given samples were determined using open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. EBSD observations showed that the imposed strain resulted in an obvious reduction in grain size to ~1.42 µm and ~0.24 µm after the first and second ECAP passes, respectively. Electrochemical tests revealed that the corrosion resistance of the ECAP-processed AlSi10Mg alloy improved significantly, which was confirmed by a nobler Ecorr and lower Icorr values, and higher polarization resistance. The final results indicated that the strain-induced crystalline defects provided more nucleation sites for the formation of a denser and thicker oxide film, thus enhancing the corrosion resistance of the AlSi10Mg alloy.

Effects of Built Direction and Deformation Temperature on the Grain Refinement of 3D Printed AlSi10Mg Alloy Processed by Equal Channel Angular Pressing (ECAP)

“…These grains originate at the lower boundary of the molten pool (see black dotted lines) and grow predominantly in the Z-direction when the solidification boundary moves opposite to the direction of heat transfer. A similar observation has already been made by many researchers [ 27 , 28 , 29 ].…”

Dilation Characteristics of 3D PBF-LB/M AlSi10Mg Alloy

“…shows a similar microstructure to that reported in the literature [48], where the laser scanning made the trace boundaries appear more etched, with smaller crystals of different crystallographic orientations also visible. With regard to the microstructural characteristics, the evaluation data are shown in Table 4.…”

Mechanical characteristics and crystallographic texture of AA5083 during Equal Channel Angular Pressing Technique

“…In the simulation, the ECAP die and plunger were visualized by extracting them from the transverse section in Figure 6. illustrates the stress distributions at the center and periphery under identical conditions, plotted as functions of the plunger stroke [23]. These stress distributions provide insights into the variations in strain experienced by the AA5083 billets processed using the 90 0 and 120 0 dies.…”