Enhanced Corrosion Resistance of Recycled Aluminum Alloy 6061 Chips Using Hot Extrusion Followed by ECAP

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.

Recent Advancements in Material Waste Recycling: Conventional, Direct Conversion, and Additive Manufacturing Techniques

“…Haase et al [261] recycled machined AA6060 aluminum alloy chips using hot extrusion and subsequent cold extrusion. Taha et al [262] recycled AA6061 aluminum alloy chips using the hot extrusion process followed by equal channel angular pressing (ECAP) and observed enhancement in corrosion resistance of the material. Selmy et al [263] recycled AA6061 aluminum alloy chips using hot extrusion process followed by ECAP.…”

“…Aluminum alloys [260][261][262][263][264][265]267], bronze [266], reinforced magnesium matrix composite [275].…”

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

“…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.…”

Effect of ECAP Routes on Mechanical Properties and Microstructure of AA6061-T4 Recycled Chips

“…Surprisingly, Kadir et al [23] applied hot compact (homogenization) to AA6061 recycled aluminum alloy chip and aluminum powder samples prior to extrusion at different preheating temperature periods extending from twenty minutes to six hours. AA6061 alloy chips were recycled by Taha et al, [24]. Using a die with a 90° angle.…”