Abstract
The oxidation of aluminum machining chips retards the successful recycling through the conventional remelting route. A promising approach to overthrow this problem is the utilization of solid state recycling in converting aluminum machining chips directly into semifinished products to eliminate the cost of the remelting process and reduce CO2 emissions. Therefore, in recent work, chips of aluminum alloy (AA6061) were recycled by compaction and then extrusion conducted at 500°C, followed by equal channel pressing (ECAP) to study the resultant material properties and its microstructure. Moreover, the present investigation explores the influence of ECAP after hot extrusion on the corrosive behaviour of the recycled samples in saline solution (NaCl) by electrochemical impedance spectroscopy (EIS) and linear polarization (LP). The results demonstrated a remarkable enhancement of the recycled chips’ properties subjected to hot extrusion followed by the ECAP process. Furthermore, the successive ECAP passes leads to increased film thickness and decreased corrosion rate.
Highlights
Conventional recycling of aluminum scrap through remelting is always accompanied with high energy consumption and material losses up to 20% due to the intensive oxidation of the molten metal [1]
The microstructure of the extruded specimen at 500°C consists of smaller grain sizes of about 15.9 μm grain size, as shown in Figure 3. e finer grained microstructure can be explained by the intense plastic deformation executed during the machining, hot extrusion, and equal channel pressing (ECAP) processes, as well as chip boundaries that act as obstacles between grains to constrain grain growth [5, 7, 24]. e grain size reduction is in concordance with the previous work presented by Haase et al [5], and the grain size of AA-6060 recycled samples extruded at 450 and 550°C was smaller than the as-received alloy
linear polarization (LP) is the last technique in the testing protocol, it will be treated first to allow for a broad overview of the process under study
Summary
Conventional recycling of aluminum scrap through remelting is always accompanied with high energy consumption and material losses up to 20% due to the intensive oxidation of the molten metal [1]. In the reported state of the art, two main lacks are observed: (a) ECAP at room temperature is more efficient in producing high strength materials due to the finer microstructure and lower energy consumption as compared to the same process at a higher temperature; almost no one, according to the authors knowledge, has considered the combination of hot extrusion followed by ECAP at room temperature. Us, the present work aims at investigating the feasibility of solid state recycling through cold compaction and hot extrusion followed by ECAP at room temperature and, exploring the influence of the hot extrusion process and ECAP number of passes on the microstructure development, mechanical properties, and corrosion performance of the as-recycled samples. An Autolab PGSTAT 30 with FRA module was employed. e EIS measurements were performed in the 10 kHz to 1 Hz
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