Effect Of Zinc Addition on The Microstructure and Mechanical Properties of AA6063 Aluminium Alloy

*Corresponding author: Oluwaseyi Adedeji Adeniyan Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution License 4.0. Effect Of Zinc Addition on The Microstructure and Mechanical Properties of AA6063 Aluminium Alloy Oluwaseyi Adedeji Adeniyan * Department of Metallurgical and Materials Engineering, Faculty of Engineering, University of Lagos, Nigeria. Global Journal of Engineering and Technology Advances, 2025, 24(03), 360-372 Publication history: Received on 16 August 2025; revised on 21 September 2025; accepted on 24 September 2025 Article DOI: https://doi.org/10.30574/gjeta.2025.24.3.0287 Abstract This research work entails addition of Zinc metal to the 6063 aluminium alloy series. The Zinc addition ranged from a percentage of 1% - 5% at an interval of 0.5%. Charge calculations were made and the aluminium alloy and Zinc were melted in a crucible furnace. Permanent mold casting was utilized with dimension of 150mm * 15mm. The 6063 aluminium – Zinc alloy were machined to standard tensile dimensions of G.D 5mm, G.L 40mm, external diameter 8mm, two opposite external length of 30mm; hardness dimensions of 20mm * 20mm * 20mm;and impact dimensions of length 60mm, diameter 10mm, notch at 30mm with 3mm depth. The aluminiumzinc alloys were heat treated to 300oC and 400oC; and held at a soaking time of 2 hours, allowed to cool in the furnace and another series of aluminium - zinc alloy were not heat treated. The specimens were destructively tested and the homogenized 400oC aluminium-zinc alloy possessed the greatest strength of 237MPa, a hardness value of 113HV, a maximum percentage elongation of 22.5% and a maximum impact energy of 70.5J. Thus, the alloy can be used for applications requiring high strength and hardness coupled with low ductility. Keywords: Aluminium – zinc alloy; Hardness; Impact energy; Strength 1. Introduction One of the key challenges of the 21st century will be the creation of materials with the ability to operate under different services or loading applications in different media such as space, air, or sea. The materials-community is uniquely positioned to play a central role in addressing these problems by fundamentally changing the materials process used by the society [1]. For this to happen, materials experts must begin to consider the environmental impacts of their design choice and will require additional analytical tools to quantify those broader implications [2]. This paper addresses the need to show that a material can withstand service/loading application under different environmental conditions using Aluminium 6063 alloy as a case study. Materials Engineers must integrate the tetrahedron of properties, processing, structure and performance of materials to create reliable manufactured or fabricated goods of great performance [3]. Of importance to their individual natures, however, is the synergistic manner in which they interact and influence one another. Clearly, the performance of an aluminium structured passenger car reflects the processing or way it was manufactured, which in turn influences the atomic and electronic structure of the constituent materials and the properties each exhibit [4]. The first important structural applications of aluminium were found in passenger hydrofoils. These were highly sophisticated vessels and the know-how developed during this technological experience formed a precious base for subsequent developments [5]. The use of aluminium combined with the use of water-jet propulsion made it possible to create a new category of vessels, the so-called high-speed ferries, single-hulled boats or more often catamarans, made Global Journal of Engineering and Technology Advances, 2025, 24(03), 360-372 361 entirely of aluminium [6]. In structural load-bearing components, 82% of a Boeing 747 aircraft and 70% of a Boeing 777 aircraft is aluminium. Aluminium usage in automobiles and in light trucks has been increasing steadily. As early as 1990, there were no aluminium-structured passenger cars in production anywhere in the world, but in 1997, Audi A8 and Plymouth Prowler amongst others came into existence, with weight savings of up to 47% over steel vehicles, such cars use less fuel, create less pollution, and are recyclable. As a result new alloys and new design and manufacturing methodologies had to be developed [7]. For example, welding and adhesive bonding procedures had to be refined, structural frame work had to be remolded and new tooling designs for the formation of aluminium was made. Because of these new technologies, the desired environmental savings were realized without any drop in performance or safety [8]. The scope of this work is limited to the following: Casting of 6063 aluminium alloy with varying percentage of zinc metal from 1% - 5% followed by heat treatment. Also included in this study is the determination of mechanical properties like ultimate tensile strength, hardness, impact strength and microstructural analysis. The significance of this study is the need for aluminium to be used in various applications where strength and hardness is required. Aluminium 6063 which when alloyed with zinc by the casting process and further heat treated improves the strength of the composite as would be proved by the results obtained in the experiment. The aim of the present work is to improve the mechanical properties of the aluminium 6063 alloy by alloying with zinc from a composition of 1% -5%. Aluminium - zinc alloys has been proven to be useful industrially in such areas which include: component parts of automobiles (in engines or carburetors) internal casement of airplanes [9]. Aluminium 6063 alloy is well known to be used in the architectural design of windows, doors and zinc is known to be used in galvanizing, coating and surface finish [10]. The alloying of zinc with aluminium 6063 alloy would find application in architecture, automobile, airspace, engines, research and can be used in any other application where necessary. The results obtained after the experimentation would determine the usage of this composite alloy in different environmental conditions. 2. Material and method The 6063 aluminium alloy material used was obtained from Nigerian Aluminium Extrusion Company (NIGALEX) at Apapa, Oshodi, Lagos. The chemical composition of the alloy was analyzed at Aluminium Rolling Mill, Ota-Ogun State and is given in the table (1) below. Table 1 Chemical composition of 6063 Aluminium Alloy Element Si Fe Cu Mn Mg Na % composition 0.66665 <0.24315 0.01643 0.02103 0.45346 0.00614 Element Ti B Sn Pb Zn Al % composition 0.00895 0.00064 0.00390 -0.00380 0.01415 98.52 The Zinc metal was purchased from a metal merchant at Iyana Ipaja, Lagos. The Chemical analysis of the zinc metal was analyzed at the Chemistry Department, Faculty of Science, University of Lagos and given in the table (2) below. Table 2 Compositional Analysis of Zinc metal Element Zn Fe Cu Cr Mn Pb Ni % composition 89.331 4.040 0.015 0.468 0.371 0.010 0.045 The Crucible furnace used in the experiment was heated to a temperature of 800oC in which the 6063 aluminium alloy were charged into the furnace and melted. This was done in order to reduce the weighed quantity of 6063 aluminium alloy in kilograms (Kg) to small size ranges ready to be casted with the zinc metal. The melted 6063 aluminium alloy were weighed to the required size together with the zinc metal and charged into the crucible furnace. A permanent mold was obtained from the metallurgical workshop and this was used for the casting operation. The melted 6063 aluminium and zinc metal were heated and obtained in molten form after heating in the crucible furnace. The molten alloy is then removed from the furnace and stirred to remove any form of impurities such as slag before being poured rapidly into the permanent mold and allowed to solidify. After solidification of the molten metal composite, cooling occurs and the cast is removed from the permanent mold. Global Journal of Engineering and Technology Advances, 2025, 24(03), 360-372 362 Table 3 Percentage Alloy And Weight Composition Of Specimens S/ N ALUMINIUM 6063 ALLOY (%) ZINC (%) ALUMINIUM 6063 ALLOY (g) ZINC METAL (g) X 100 0.0 200 0 IX 99.0 1.0 194 6 VIII 98.5 1.5 191 9 VII 98.0 2.0 188 12 VI 97.5 2.5 185 15 V 97.0 3.0 182 18 IV 96.5 3.5 179 21 III 96.0 4.0 176 24 II 95.5 4.5 173 27 I 95.0 5.0 170 30 The as-cast materials after fettling were machined to standard tensile test piece, impact test piece and hardness test piece. The larger diameter end of the impact test piece was cut off for spectrometer analysis. As the specimens were being machined, the tendency of the cutting tool to damage due to overheating was reduced by the use of cutting fluids. The heat treatment used for this project is homogenization heat treatment. This involves setting the furnace temperature to 300oC, 400oC. Therein the samples are held at a soaking time of 2 hours. They were cooled in the furnace till the next day and then removed for determining their mechanical properties. The heat treatment process was carried out at Metallurgy laboratory, University of Lagos. The use of a file was utilized to provide an initial flat surface and subsequent grinding took place on the rotary grinding wheel using silicon carbide abrasive papers of various grades. Water was used to avoid overheating and grinding on each paper progressed until the scratches produced by previous grinding operations were completely removed. The purpose of polishing was to remove the surface scratches in order to obtain a mirror surface. A polishing powder was utilized as well as water to reduce heat generated from the rotating wheel. In order to reveal the structure, the specimens were etched in a solution containing Sodium Hydroxide NaOH for 30seconds and then washed with water and allowed to dry. The etched surface was viewed under the metallurgical microscope and the photographs were taken. The samples were machined according to standard for tensile and impact specimens for mechanical analysis of tensile strength, impact strength and hardness. TENSILE TESTThis was carried out on an Instron Universal tester,3369 model at the Engineering Materials Development Centre, Km 4 Ondo Road, Akure, Nigeria. IMPACT V-NOTCHED TEST – The cast samples were tested using the Avery impact testing machine. This was carried out at the stress-strain analysis laboratory, Mechanical Department, University of Lagos. HARDNESS TEST – The hardness test was done using a Leco Micro hardness tester model at the Engineering Materials Development Centre, Km 4 Ondo Road Akure, Nigeria. Global Journal of Engineering and Technology Advances, 2025, 24(03), 360-372 363 3. Results and Discussion 3.1. Tensile Test Results Figure 1 True Stress Vs True Strain for 5% Zinc Addition From Figure 1; the true stress vs. true strain shows that the homogenized 300oC alloy undergoes sufficient plastic deformation before fracture indicating the largest ductility with maximum UTS of 125.08MPa. From Figure 2; the unhomogenized alloy possesses the highest UTS of 164.16MPa while that of the Homogenized 300oC alloy possesses the largest plastic deformation before fracture thereby making it more ductile. From Figure 3; the homogenized 400oC alloy has the maximum UTS of 275.39MPa while the homogenized 300oC alloy undergoes sufficient plastic deformation. Figure 2 True Stress Vs True strain for 4.5% Zinc Addition Global Journal of Engineering and Technology Advances, 2025, 24(03), 360-372 364 Figure 3 True Stress Vs True strain for 4% Zinc Addition Figure 4 True Stress Vs True strain for 3.5% Zinc Addition From Figure 4; the unhomogenized alloy has the greatest UTS of 144.84MPa and undergoes sufficient deformation while the homogenized 400oC alloy has the largest deformation. From Figure 5; the homogenized 400oC alloy has the least deformation and the highest UTS of 172.82MPa while the homogenized 400oC alloy undergoes sufficient plastic deformation. From Figure 6; the unhomogenized alloy has the maximum UTS of 143.51MPa and undergoes sufficient plastic deformation. From Figure 7; the homogenized 400oC alloy undergoes the least deformation with a UTS of 124.76MPa while the homogenized 300oC alloy undergoes sufficient plastic deformation. From Figure 8; the homogenized 300oC alloy has the maximum UTS of 122.72MPa and undergoes sufficient plastic deformation as shown. Global Journal of Engineering and Technology Advances, 2025, 24(03), 360-372 365 Figure 5 True Stress Vs True strain for 3% Zinc Addition Figure 6 True Stress Vs True strain for 2.5% Zinc Addition Figure 7 True Stress Vs True strain for 2% Zinc Addition Global Journal of Engineering and Technology Advances, 2025, 24(03), 360-372 366 Figure 8 True Stress Vs True strain for 1.5% Zinc Addition Figure 9 True Stress Vs True strain for 1% Zinc Addition From Figure 9; the unhomogenized alloy has the maximum UTS of 106.4MPa while the homogenized 400oC alloy undergoes sufficient plastic deformation. From Figure 10; the homogenized 300oC alloy has the maximum UTS of 134.52MPa and undergoes the highest plastic deformation. Figure 1.10 True Stress Vs True strain for control sample - 100% Al alloy Global Journal of Engineering and Technology Advances, 2025, 24(03), 360-372 367 3.2. Ultimate Tensile Strength Graph Figure 11 Comparison of UTS for Homogenised and Non-Homogenised Alloys UTS: From Figure 11; the homogenized 400oC alloy possesses the highest UTS of 237MPa from an increasing percentage zinc addition of 4% while that of unhomogenized alloy shows an increasing UTS from a corresponding percentage increase in zinc addition with a maximum UTS of 148MPa and homogenized 300oC shows a fluctuating increase in strength from a corresponding percentage increase in zinc at a maximum UTS of 135MPa. Hardness Test Graph Figure 12 Comparison of Hardness for Homogenised and Non-Homogenised Alloys Hardness: From Figure 12; four readings were taken for each specimen and the average found and plotted against percentage zinc addition as shown. The Homogenised 400oC alloy possess the highest hardness value of 113HV (Vickers HardnessHV) followed by the homogenized 300oC alloy with a hardness value of 66.8HV and the Unhomogenized alloy with a maximum hardness value of 66.3HV all with an increasing percentage of zinc addition. Global Journal of Engineering and Technology Advances, 2025, 24(03), 360-372 368 3.3. Impact Strength Graph Figure 13 Comparison of Impact Strength for Homogenised and Non-Homogenised alloys Impact: From Figure 13; the Homogenized 300oC alloy shows maximum impact energy of 81.35J with an increasing zinc addition also the Unhomogenized alloy shows a maximum impact energy of 73.21J while that of Homogenized 400oC alloy shows a maximum impact energy of 70.5J 3.4. Ductility Graph Figure 14 Comparison of % Elongation for Homogenised and Non-Homogenised alloys