Temperature and Reduction Ratio Effects on Wear Rate and Ductility of Direct Extruded Aluminium 6063: A Numerical and Experimental Investigation

Aluminium alloys, most especially 6063 grades, have gained popularity in many industrial applications owing to their distinguishing features such as lightweight, corrosion resistance, high strength, thermal and electrical conductivity. These features enable them to be suitable for transportation, aerospace, and construction applications [1]. It resembles the British aluminium alloy HE9 due to its similar properties in terms of strength and weldability [2]. One of the major practical techniques of producing and enhancing aluminium alloy qualities is extrusion, a procedure that entails the material being forced through die to produce complex shapes.

Extrusion is a method of manufacturing shapes from plastic or metallic materials by forcing them through a prefabricated series of dies. The extruded product takes the die shape [3]. The extrusion process is unique relative to other forming processes, such as forging and casting, due to its ability to produce longer shapes, such as tubes and beams, which are not realistic in forging and casting processes [4]. Extrusion also enables more accurate shape and size control of the product profile. This process conserves more materials compared to machining, which is also one of the forming processes [5]. The extrusion process is well-suited for aluminium alloys due to its low melting points, high ductility, and corrosion resistance [6]. The process enables the development of complex shapes, and it is cost-effective with high efficiency.

Aluminium extrusions have gained production popularity in many ways, examples of these are found in window frames manufacturing, aircraft components, and taking advantage of their thermal conductivity in the production of heat sinks used in electronic devices. Extrusion responses, otherwise known as process parameters like reduction ratio and temperature, are substantially enhanced by the mechanical features, performance, and micro-structural value of the extruded product [7]. Flow stress, microstructural texture, and ductility of the material have been influenced by the temperature [8]. The reduction ratio also enhanced strain hardening and fine texture development [9]. A thorough understanding of these parameters’ impacts on the extrudes is very important in optimizing the extrusion process and ensuring high-quality products. However, past research concentrated on individual temperature or reduction ratio effects without any details on their interactive effects [10]. This knowledge gap restricted the prediction and control ability of the mechanical properties and microstructure of the extrudes.

The two crucial properties that are used as a measure of extruded aluminium components' performance and lifespan are ductility and wear resistance [11]. Wear resistance is crucial for friction and abrasion applications like moving parts and surfaces [12]. Ductility is important in an application that requires deformation to be prevented so as to prevent failure [13].

To obtain superior mechanical qualities, the interactions between extrusion process parameters, particularly reduction ratio and temperature, are critical [14]. According to Laptev et al. [15], the temperature development is a bit greater in initial billet height at a given percentage area reduction, and the greater the percentage reduction in area, the higher the temperature rises during the extrusion process. This is because, when the amount of energy required to distort the material advances, it so increases the deformation work in addition to frictional work, particularly at the die land zone, which transforms into heat in the main deformation and die land zone [16]. Beyond a 90% area decrease, the dead zone temperature often rises considerably more than the die region temperature. This is attributable to the direct and greater contact area of this zone with the major deformation region, along with the substantial degree of heat flowing into and released in this zone during the transformation of the deformation work into heat [16]. Increasing the coefficient of friction causes an increase in extrusion temperature at the die land zone but no substantial increase in extrusion temperature at the dead zone. However, exceeding an extrusion speed of 4.23mm/s results in a higher dead region temperature rise than a steadier die land temperature increase. In general, increasing speed causes a temperature rise [16].

The excessive or insufficient reduction ratio and temperature effects are posing a threat to the extrusion process. Work piece may be damaged under excessive temperature, like hot tears, blisters, and incipient melting, especially at the temperature exceeds 550℃ [17]. Excessive reduction ratio can subject materials to overworking conditions that consequently result in fractures and cracks. In the reverse way, too low a reduction ratio and temperature can lead to under-pressing, resulting in inadequate mechanical properties or surface roughness defects. Based on previous studies, extruding materials under excessive temperature can hike the cost of extrusion up to 16% because of wasted energy and die wear [3].

Despite the extrusion parameter’s role on aluminium 6063 properties, there is an urgent need for a thorough review on the combined extrusion parameters, such as temperature and reduction ratio effects on its ductility and the wear rate. This research aims to bridge the gap between using combined experimental and numerical techniques in investigating temperature and reduction ratio effects on ductility and wear rate of extruded aluminium 6063.

Through the extrusion process and materials properties comprehensive analysis, this study seeks to present a significant insight into the sophisticated interactions between extrusion parameters, micro-structure and its performance. The research outcomes will contribute immensely to developing the optimized extrusion processes and enhanced materials properties, leading to improved efficiency and sustainability of industrial applications.

The study comprehensively investigated the relationships between processing parameters, microstructure, and mechanical properties of Al 6063 aluminium grade, and its application of statistical design of experiments (DOE) techniques for optimization, as a result, the following conclusions were drawn from the research.

i. Both temperature and percentage reduction rate significantly enhance ductility and wear rate.

ii. The relationships between processing parameters, microstructure, and mechanical properties of extruded Al 6063 were established and all the input factors and some of their interactions are significant in wear rate and ductility predictions through the developed model.

iii. The application of CCD for optimizing the extrusion process allows the evaluation of multiple factors and their interactions.

iv. Extrudates at higher percentage reduction has reduced wear rate and higher ductility.

v. Higher percentage reduction ratio refine grain structure of aluminium 6063.

vi. The findings of this research can be applied in various industries, such as aerospace, automotive, and construction, where extruded Al 6063 alloys are widely used to forecast its properties.

vii. The integrated experimental-simulation approach enabled the development of a more accurate simulation model, capturing the complex interactions between processing parameters and material properties.

viii. The validated experimental model and simulation that were used to optimize the extrusion process will reduce trial-and-error experimentation and improve the efficiency of the process.

ix. The integrated approach has provided a deeper understanding of the material's behavior during extrusion, enabling the development of new materials and processes.

Future studies could consider using non-linear statistical models, in deciding normality and transforming the data if necessary, increasing the sample size, and considering additional variables that may affect the relationship between extrusion parameters and material properties.