Microstructural Evaluation and Corrosion Resistance of Semisolid Cast A356 Alloy Processed by Equal Channel Angular Pressing

Gebril, Mohamed A.; Omar, Mohd Zaidi; Mohamed, Intan Fadhlina; Othman, Norinsan Kamil

doi:10.3390/met9030303

Cited by 13 publications

(9 citation statements)

References 60 publications

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“…During the formation of DHES, the RS machining chips undergo a series of deformations (mechanical cutting, compaction, extrusion at elevated temperature with dimensional changes), during which the eutectic Si and intermetallic phases are significantly refined and uniformly redistributed into the fine-grained α-Al matrix so that the resulting DHES microstructure is homogeneous and refined (Figure 3). In this way, a larger number of galvanic microcells are formed between ultrafine Si particles (or IMCs) and α-Al grains, resulting in a favourable small cathode/large anode combination and reducing the susceptibility to pitting corrosion [28]. It should not be forgotten that this process generates a larger number of grain boundaries, a greater proportion of unbalanced grain boundaries, dislocations, and residual stresses in the machined sample.…”

Section: Surface Analysis After Corrosion Measurementsmentioning

confidence: 99%

“…Solid recycled specimens exhibited an excellent combination of high strength and high elongation to failure at room temperature, which was attributed to the refined microstructure, but lower corrosion properties, attributed to the excessive iron contamination that promoted galvanic corrosion [25]. Several researchers have investigated the influence of ECAP on the corrosion properties of aluminium alloys [26][27][28][29][30][31]. They found that the ECAP processing facilitated passivation, increased the thickness of the oxide layer, and the decreased corrosion rate, which was attributed to the significantly reduced grain size in solid recycled specimens.…”

Section: Introductionmentioning

confidence: 99%

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Corrosion Behaviour of Recycled Aluminium AlSi9Cu3(Fe) Machining Chips by Hot Extrusion and Thixoforming

Gudić,

Vrsalović,

Krolo

et al. 2024

Sustainability

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The corrosion properties of an EN AC AlSi9Cu3(Fe) alloy (reference sample (RS)) and samples produced by recycling chips of RS by direct hot extrusion (DHES) and subsequent thixoforming (TFS) were tested in 0.5 M NaCl solution. The plastic deformation changes the microstructure of RS, and brittle, coarse Si particles and intermetallic compounds (IMCs) were effectively broken into ultrafine-grained particles and redistributed homogeneously into the α-Al matrix in DHES. TFS exhibits a globular structure, and polyhedral clusters rich in Si and IMCs were observed along the grain boundary. Electrochemical measurements combined with surface characterisation show that the microstructure significantly influences the tested samples’ corrosive properties. It was confirmed that corrosion resistance increased in the following order: RS < TFS < DHES. Similarly, the corrosion potential becomes nobler, the corrosion current decreases, the passive area increases, and the oxide layer becomes more stable (higher resistance and thickness). Also, the percentage of the surface affected by corrosion and the volume of pits reduce. The effect of microstructure is particularly pronounced in the level of the corrosion current and the volume of pits formed. The corrosion current of DHES and TFS decreases by 4–5 times, while the pit volume of DHES and TFS decreases by several orders of magnitude compared to RS. The corrosion stability of DHES and TFS in relation to RS is a consequence of the comminution of the Si particles and the IMC. The refined and homogeneous microstructure contributes positively to forming a stable oxide film on DHES and TFS and increases their corrosion resistance in an aggressive environment. The applied recycling method represents an innovative and sustainable process for the recycling of semisolid materials, with lower energy consumption and less greenhouse gas emissions compared to conventional recycling. The fact that the products obtained through recycling have a significantly higher corrosion resistance further increases the economic and environmental impact of the process.

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Section: Surface Analysis After Corrosion Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Corrosion Behaviour of Recycled Aluminium AlSi9Cu3(Fe) Machining Chips by Hot Extrusion and Thixoforming

Gudić,

Vrsalović,

Krolo

et al. 2024

Sustainability

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“…In this study, it was reported that the forced convection induced by TMF break the dendrites, refine the grain size, and promote liquid feeding, leading to a decrease in the volume fraction of the porosity and improved mechanical property. The microstructural evaluation and corrosion resistance of a semisolid Cast A356 alloy were studied by Gebril et al [2]. For that, a combination of as-cast and semisolid casting using a cooling slope processed by equal channel angular pressing (ECAP) was used.…”

Section: Casting Aluminum Alloymentioning

confidence: 99%

Casting and Forming of Advanced Aluminum Alloys

Puga

2020

Metals

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“…Furthermore, these techniques are expected to serve as alternatives to traditional casting processes because they offer the possibility of constructing defect-free, heat treatable and near-net shape components at low cost [ 8 , 9 ]. This approach produces materials that possess homogeneous globular microstructures that are characterised by decreased segregation and porosity [ 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Semisolid and Heat Treatment Process on Microstructural Refinement of Al–7Si Alloy

et al. 2023

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Improving the engineering properties of Al–7Si cast alloys (300 series) provides an attractive alternative to automotive and aircraft engine industries. The solubility limit of silicon (Si) in Al contributes to the precipitation of flake-shaped Si particles with sharp edges, which function as a stress riser and promote crack propagation during the eutectic phase while also weakening the protective layer’s durability. In this study, the impact of microstructure refinement of Al–7Si alloys by using cooling slope, thixoforming and the T6 heat treatment process on hardness and corrosion resistance behavior was investigated. Results showed that the microstructures of the as-cast alloy had a very coarse dendritic shape, whereas the dendritic transferred to the globular α-Al phase, and the Si particles were replaced into a lamellar- or acicular-like shape after the cooling slope and thixoforming process, respectively. The as-cast, cooling slope and thixoformed samples were subjected to the T6 heat treatment process, which enhanced the hardness to 79, 99 and 104 HV, respectively, due to Si particle refinement. The potentiodynamic test revealed that the corrosion rate dropped to 0.00790 and 0.00736 mmpy−1 in the heat-treated cooling slope and thixoforming samples. This finding can be attributed to the substantially refined Si particles and reduced eutectic phase area due to the smaller cathodic to anodic area ratio.

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Microstructural Evaluation and Corrosion Resistance of Semisolid Cast A356 Alloy Processed by Equal Channel Angular Pressing

Cited by 13 publications

References 60 publications

Corrosion Behaviour of Recycled Aluminium AlSi9Cu3(Fe) Machining Chips by Hot Extrusion and Thixoforming

Corrosion Behaviour of Recycled Aluminium AlSi9Cu3(Fe) Machining Chips by Hot Extrusion and Thixoforming

Casting and Forming of Advanced Aluminum Alloys

Effect of Semisolid and Heat Treatment Process on Microstructural Refinement of Al–7Si Alloy

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