Characterization of wear and fatigue behavior of aluminum piston alloy using alumina

: Due to their excellent thermal conductivity, lightweight, and ease of processing, aluminum alloys are the material of choice for piston manufacture in internal combustion engines. Nanoparticles ( NPs ) of alu - mina ( Al 2 O 3 ) with a size of 25 nm were incorporated into an aluminum piston alloy to examine the e ﬀ ect of the NP addition on wear resistance and fatigue behavior. The stir casting method has been utilized to manufacture experi - mental samples of the composite material by altering the particle weight ratio of aluminum to the matrix alloy to 2, 4, and 6 wt%. The surface morphology of the samples has been examined using an electronic scanning microscope. The results of the wear and fatigue tests indicate that the addition of Al 2 O 3 to the composite enhanced its fatigue resistance and wear strength, with the exception of 6 wt% weight ratio. The best improvement in wear resistance and fatigue strength occurs at 4 wt% Al 2 O 3 particles, which are 12.13 and 67.5%, respectively, more signi ﬁ cant than the pure metal and other composites. The mechan - ical properties of the alloy samples have been enhanced by adding Al 2 O 3 NPs of 25 nm size into the piston ’ s alu - minum matrix alloy. Stir casting was employed to pro - duce the needed composites by incorporating Al 2 O 3 NPs at varied weight percentage ratios of 0, 2, 4, and 6 wt% into the master alloy. Before the composite alloy reached 6 wt%, including Al 2 O 3 NPs, the alloy ’ s hardness and tensile strength improved, according to the experiment results.


Introduction
The purpose of the piston is to transfer the force generated in the power stroke by the extension gas via a connecting rod and the crankshaft of the machine cylinders [1]. Because of this function, the piston is exposed to fatigue and wear while producing power. Wohler was the first researcher to define the concept of "fatigue" to explain material degeneracy. The failure is proportional to the number of cycles of applied load and the fatigue damage is one type of brittle fracture under cyclic loading [2,3]. Most engine combustion (IC) pistons are made of Al 2 O 3 alloys. The piston temperature must be above 66% at around 600°C [4,5]. In the mechanical characteristics of the piston material, the aluminum column alloys play an active part in various intermetallic phases, including Cu 3 Al, and Mg 2 Si morphology and their distribution. Therefore, the abovementioned material was subjected to different thermal aging treatments [6]. A research study briefly addresses the fatigue conduct of additive manufacturing (AM) with various problems influencing the actions. In contrast with conventional production processes, AM strategies have several advantages. Besides the opportunity to render components that are always difficult with complicated geometries, it ensures the economical and efficient production of parts in small numbers. Because of these factors, AM processes in different sectors have become more common, especially for aerospace, biomedical, and, more lately, automobile applications [7]. In an experimental procedure, four kinds of heat treatments carried out in four investigations assessed the fatigue performance of steel CK45. The study showed that the fatigue life of oil quenching has better lives and exhaustion than other cases [8]. A comparative study of the casting of aluminum alloys by Al-Si-Cu showed the fatigue effect of air and vacuum. The study's principal findings showed that vacuum fatigue lives are longer than in air [9]. In aluminum 2024, alloy strengthened in the presence of silicon carbide and artificial aging at 170°C have been proven to increase the strength of fatigue [10]. The mechanical properties of 2024 aluminum alloy composites with Al 2 O 3 particulate additive have been studied for the effect of cryogenic temperature. Surely, cryogenic therapy enhanced fatigue, hardness, and grain size [11]. The gray cast iron was added with micro-chromium material as a weight ratio. Enhanced micro-toughness and wear resistance of the Al 2 O 3 /TiO 2 nanoalloys dispersed hyperesthetic A390 from laboratory tests [12]. The influence of SiO 2 insertion of various nanoparticle (NP) concentrations increases the base matrix's hardness [13]. To analyze the changes in the composite's hardness, a compo-casting method was developed to manufacture A356 micro-and nano-sized Al 2 O 3 regenerated composites. The results showed that the hardness increased with increased particle weight fraction and decreased particle size [14,15]. It is concluded from the results of a comparison study between sand-cast Mg-10Gd-3Y-0.5Zr magnesium alloy with sand-cast plus T6 heat-treated magnesium alloy that the fatigue strength can be improved from 95 to 120 MPa when magnesium alloy increases by 26% after T6 heat treatment [16].
Most published articles are based on literature context data on improving the composite matrix's mechanical and tribological characteristics, including tensile strength and hardness. Nevertheless, none investigate the addition of Al 2 O 3 NPs on fatigue strength and piston materials' wear resistance [17]. Detonation happens when the compression ratio is higher than the fuel's octane rating, which is problematic. One of the principal outcomes is a break or fracture on the piston head, as depicted in Figure 1. This analysis has been provided to reduce the impact of the damage. To improve the mechanical characteristics of the piston materials produced by aluminum alloy EN AB-47100 AlSi 12 Cu 1 (Fe), Al 2 O 3 NPs were selected as one of the ceramic additions. Based on information from the literature, the obtained alloy had three distinct weight percentage ratios of Al 2 O 3 NPs of 25 m size added using the stir casting process at a given time and speed. Experimental research was carried out to determine how adding of NPs affected the mechanical characteristics of the piston's composite components. Abbas and Rasheed measured the mechanical properties of the Cu-doped TiO 2 NPs [18]. For other applications in this field, mathematical models have been used .
This research concerns the microstructure and mechanical characteristics of the Al 2 O 3 -reinforced addition to a row of aluminum alloy matrix. It is extended mainly on the processing, through the use of a stir casting technique of metal nanocomposites and explores the impact on the fatigue, hardness, tensile, and wear of the modern facilities of the 25 nm Al 2 O 3 NPs of size reinforced. The fracture piston issue that affects USA Chrysler Jeep vehicles undergoing maintenance when low gasoline octane number is utilized is what inspired the author to propose this work. The objective of the present work is to add Al 2 O 3 NPs with 25 nm grain size to the aluminum piston alloy to investigate the effect of NPs on the mehanical behavior of the Al alloy piston.

Fatigue test
Schenck company from Germany has been used to compute the number of cycle to failure (RPM) for the fatigue sample. The material was examined based on ASTM- E1251 for standardization and quality control (COSQC) to get the chemical configuration of the actual piston materials. The formulation of the base alloy is from fragment pistons with the trademark USA Chrysler Jeep. The initial compound configuration of the master ingredient is based on [17]. A hole furnace at 800°C temperature melts the scrap pistons in the container. The liquefied fusion was poured in iron molding warmed at a temperature of 400°C to confirm good quality fabrication. The production of the pure alloy is designed to round with (80 mm × 10 mm) diameter column. The specimen sizes are based on ASTM (E8/E8M-09) in mm; the machine used for the fatigue test is shown in Figure 2.

Wear test
Wear resistance is a terminology mainly employed to explain the wear-resistance properties of a substance. The part of the wear test has been done in the Material Department in the strength of materials lab/University of Technology, Baghdad, Iraq. Four samples were prepared to be tested in the wear device. Mass loss measurement is a function of the wear measurement. A tube-shaped specimen of 10 mm in diameter and 30 mm in length is filled alongside a flat rotational disc such that a circular wear pathway is defined by the machine rotating by an electrical motor. The device can measure material wear and friction under pure sliding conditions. The first step is to measure the weight of each sample before doing the test with a sensitive measuring device reading up to five digits, as in the figure. The wear device is manufactured locally in the material department lab. The speed used for the test was 950 rpm, and the force (load) used for the test was 25 N. When doing the test, the disc and the sample were cleaned clearly to gain the minimum error measurement. Calibration to the device was taken each time before operating the machine to keep the arm device's linearity in the correct position. The experiment was repeated four times for the four samples. The time selected for the experiment is fixed at 10 min. The slip distance between the disc's center diameter and the sample's center was 65 mm.

Hardness test
The specimens' measurements were performed using the Vickers hardness (HV) test method with a diamond indenter to determine the hardness of the samples. Three indentations were taken, and their average was calculated to achieve an accurate reading. HVS-1000 Digital Micro Hardness Tester (Laryee Technology Co., Ltd) from China was used.

Tensile strength
Tensile strength was determined using the compression testing machine from Laryee Technology Co., Ltd, China.

Results and discussion
3.1 SEM images Figure 3 illustrates the surface morphology of samples with 0, 2, 4, and 6 wt% ratio addition of Al 2 O 3 NPs for the pistons matrix alloy. All depicted images are with the specification of HV 5 kV, Mag. 50k×, and SEM images at 200 nm particle size. It indicates the aggregation of Al 2 O 3 particles to the shape of the non-regular allocation causing non-homogeneity of the composite. This may be due to parameters such as stirring speed and stirring time.

Fatigue test
The obtained result of the fatigue test is recorded in Table 1 and Figure 4. In general, the fatigue life (number of cycle to failure) increases as the ratio of Al 2 O 3 particles increases. The best result is obtained when the NPs are 4 wt% weight

Wear test
The results of the wear test for each experiment are listed in Table 2. The weight for samples was taken before and after wear testing, and the difference in the weight was obtained. The weight difference before and after the test indicates the weight loss in (g) units as a function of wear. Figures 5 and 6 show that the machine for wear  testing has been used, and the weight lost materials decrease as the Al 2 O 3 particles' weight ratio increases up to 4 wt% by 20.3% from the received one. However, at a 6 wt% particle ratio, the weight loss increased. The increase in the weight is due to the increase in the generated heat in the friction processing, besides the non-homogenous distribution of the NP additive in the matrix.

Hardness test
HV testing was done to see how the primary alloy would be affected by the Al 2 O 3 particle extension. Each sample was subjected to an average of three measurements. The measurements of particle hardness concerning their extension are shown in Figure 7. The graph shows that the hardness typically rises as the ratio of nano-Al 2 O 3 particle weight increases since Al 2 O 3 is a complex ceramic particle combined with a soft aluminum matrix. Nevertheless, compared to the hardness with 2 wt% Al 2 O 3 NPs, the hardness with 4 wt% Al 2 O 3 NPs is lower. This reduction is a result of the matrix alloy's non-homogeneous particle distribution. The dispersion of particles in the specimen test altered the measurement readings of the Vickers testing.

Tensile strength
The primary alloys' and composites' tensile strength values are shown in Figure 8 as a function of the number of Al 2 O 3 NPs added. As shown in this figure, composite materials with less than 6 wt% Al 2 O 3 particles have greater tensile strength than the base alloy. In contrast, those with 0 and 6 wt% Al 2 O 3 particles have lower tensile strength than the base alloy. Furthermore, this figure demonstrates that the maximum tensile stress was 212 MPa of the composite containing 4% Al 2 O 3 is 35% higher than that of the matrix alloy. The tensile strength falls as the percentage, including ceramic particles, increases with 4 wt% Al 2 O 3 particles. The matrix of the alloy's non-uniformly distributed particle structure is the reason for the loss in tensile strength; this makes the composite more porous. Porosity    is the leading cause of poor adhesion at the ceramic-matrix contact.

Conclusion
The matrix aluminum-established NPs in nano-compounds are effectively supplied by the stir casting method and are assessed. The fatigue power of the iron matrix is related to the nano-particle enhancement percentage. The nanocomposite metal matrix containing scrap piston materials plus Al 2 O 3 of 4 wt% has a wear resistance of 12.13% higher than the building metal and other composites. The strengthening, grain allocation, and grain size of NPs are responsible for the nanocomposite's high-level and enhanced fatigue performance. The impact of strengthening on fatigue lifetime (the number of cycles to failure) increases with the increase in the weight percentage of reinforcement. The hardness value of the samples indicates that it increases after adding the Al 2 O 3 NPs. In general, it is concluded that adding Al 2 O 3 particles in a predetermined quantity improves the mechanical qualities. Except for the composite with 6 wt% Al 2 O 3 NPs, all experimentally tested composite materials exhibit better excellent tensile strength values than the received aluminum alloy. Because of an increase in porosity caused by the inclusion of Al 2 O 3 NPs over 4 wt%, the tensile strength drops. As the weight percentage of Al 2 O 3 NPs is added, the hardness rises. If we achieve excellent NP dispersion in the matrix alloy, the range of mechanical characteristics improvement may be expanded. The time spent stirring the composite materials in the experimental task and the speed at which the stir motor rotates determine the distribution control.