1. Introduction
The aerospace and automotive industries seek materials that are low in weight, have high specific strength, and can withstand wear, corrosion, cracking, fatigue, and heat, among other things [
1,
2]. Though conventional ferrous metals and alloys are abundant, affordable and mainly used in aerospace and automotive, they lack the properties mentioned earlier [
3,
4]. Thus, researchers and engineers prefer nonferrous metals like Aluminum, Magnesium and Titanium compared to ferrous metals for practical purposes. Despite its lightweight, Magnesium has a high proclivity for catching fire, making it unsuitable for use in the aerospace industry [
4]. Due to its high cost, titanium is rarely used in industries [
5]. As a result, Aluminium is the metal of choice in many sectors. Aluminium and its alloys are widely used in aerospace, automotive, defence, and other industries due to their lightness, strength, wear resistance, and corrosion resistance [
2,
6,
7,
8].
Aluminium-based composites are frequently fabricated with micro-sized ceramic powders and fibres as reinforcement. Composite materials have significantly improved strength and stiffness compared to unreinforced aluminium alloy materials. Particulates and fibres (short and long) are usually chosen as the reinforcing particles during the preparation of the Aluminum matrix composites. The Aluminum-based metal matrix composites can be reinforced with particulates like Ti, B
2, B
4C, SiO
2, TiC, WC, BN, and ZrO
2. However, the composites made with Al
2O
3 and SiC particles have recently been investigated for various industrial applications due to their higher stability [
9,
10].
The composite production methods can be divided into three categories: Solid-state, Semi-solid state, and Liquid state. Powder metallurgy, mechanical alloying, and diffusion bonding are the three types of Solid-state processes [
8,
11]. The approach entails a series of procedures that culminate in producing particulate-reinforced Metal Matrix Composites (MMCs) from blended elemental powders before final consolidation. It enables the use of a wide variety of materials as the matrix and reinforcement. Separation effects and the production of intermetallic phases are also less common in these processes. However, this scenario’s manufacturing process is relatively complex, time-consuming, costly, and energy-intensive [
8,
12]. The semi-solid process (SSP), which involves mixing ceramic with a matrix with solid and liquid phases, can be accomplished by various techniques, namely compocasting and thixoforging. The SSP facilitates the production of huge components while sustaining high productivity rates. The most cost-effective process for preparing MMC is liquid metallurgy. Liquid metallurgy can be divided into four categories: Pressure infiltration, Stiri casting, Spray deposition, and In situ processing. Among these, the Stir casting or Melt stirring method has several advantages over other methods. It includes a broader range of materials, improved matrix–particle bonding, easier matrix structure control, and near-net-shaped components that can be processed efficiently and cheaply, adaptable to large-scale production, and highly productive [
8,
13].
Naseem Ahamad et al. [
7] investigated the mechanical characteristics of Al-Al
2O
3-TiO
2 composite material developed using the stir casting technique. The addition of the reinforcing particles to prepare the composite material decreased the density of the composite and increased the hardness and overall strength making it more suitable for aircraft rivets. K. Kanthavel et al. [
14] studied the effects of alumina and MoS2 on the wear properties of the produced composite. The authors observed that the addition of the MoS2 acts as a solid lubricant, reducing the wear of the produced composites at high load and speed conditions. A similar trend in the results was also noticed in work done by D. Simsek et al. [
15], where the Aluminium was reinforced with Al
2O
3 and graphite and in work done by Necat Altinkok [
16], where the Al- alloy was mixed with α-aluminium oxide particles.
However, most of the articles in the literature followed the trial and error method in fixing and optimising the composition of the composite material components. Some researchers have recently used the Mixture Design for composite mixture optimisation [
9,
11,
17]. This approach is based on the statistical methodology, which provides optimal mixture components and the predictive model. Further, the Mixture design facilitates multi-response optimisation, which is highly useful for engineers in the industry and ensures Design for Manufacturability (DFM) [
18].
Based on the above discussion, the study’s objective is to determine the optimal mixture components and predictive model of Al-Si alloy with Al2O3 for different mechanical properties using the Mixture design method. More specifically, research intended to study composite material’s Hardness (BHN), Density (g/cm3), Tensile (MPa) and Impact strength (J) with an optimal combination of component mixture that facilitates DFM in the industry.
4. Conclusions
The research established a well-defined multidisciplinary methodology based on mechanical engineering, material engineering, and statistical methodologies. This methodology helped to develop composite materials and validate the mechanical properties of the materials with the optimal utilisation of available resources. Furthermore, the research shows that the Mixture Design technique enables precise optimisation of mixture components in multi-response scenarios and aids in developing better predictive models.
The results obtained through the statistical analysis showed that both Al alloy and the reinforced Al2O3 particles significantly influence the composite material. Moreover, a positive correlation was observed in the mechanical properties such as hardness, tensile strength and density. In contrast, the impact strength of the composite material was negatively correlated and vice versa.
The microstructural analysis of the produced composite materials suggested that though the reinforcing particles were mixed uniformly by creating a centre vortex while stirring, there existed a non-uniform settlement of the particles among the matrix material. The existence of the primary silicon particles, eutectic silicon particles in the form of needles and the Al2O3 particles were noticed in the images.
The reinforcing particles’ inclusion in the composite material preparation proved beneficial. Most mechanical properties, such as density, hardness, and tensile strength, have shown a positive increase in the values. With the predictive model, the mechanical properties obtained were almost in line with the values obtained through the regression equations, thus rendering the equations obtained as accurate. Thus, the study finds that the composite material produced with Al-Alloy = 94.65 wt% and Al2O3 = 5.35 wt% leads to the best results.
From a DFM and industrial standpoint, the current research delved in depth to create a multidisciplinary technique to develop, forecast, and optimise the composition of the produced material. Although multi-responses are acclimated into the study, the researchers firmly believe that to enhance the knowledge base and get a better insight into the behaviour of the newly developed composite material, the study needs to be extended to other properties like tribological, vibration as well as thermal. These studies will help industry and academia achieve these composite materials’ potential for societal benefit.