Comprehensive Study for Impure and Pure Casts of Aluminum and Copper

: Impure and pure casts have collected reasonable attentions over all the world. In this paper, Aluminum (Al) and Copper (Cu) cast alloys are considered to be studied. Multiple impure and pure Al-Cu cast alloys are established under the condition of very high temperatures. Then, all of the established alloys are examined by applying mechanical tests. More specifically, tests of hardness are exploited. Moreover, different quenching conditions are employed and analyzed. These are the water, air and oil. Consistent results are separately obtained for the impure and pure materials.


Introduction
Cast alloys are essential materials that can be used in many fields. For example, manufacturing cars, trains, airplanes and trunks. A cast alloy refers to a mixed metal between two or more elements, where various ratios of elements are melted and combined to produce the certain alloy. The resulted cast alloy has different specifications that are completely different from essential characteristics of each component element. The cast alloys can be made by a combination between two or more elements of Aluminium (Al), Copper (Cu), Zinc (Zn), Magnesium (Mg), Manganese (Mn), Silicon (Si) and others [1].   [2] Al is reported as one of the most important elements. It abundant metal in the earth where it constructs about 8% of weighted solid earth surface. It generally uses in many purposes due to its weight ratio, good corrosion resistance, low density, good formability, high strength stiffness and recycling potential [3]. It has a Face Center Cubic (FCC) crystal structure and its ductility is taken at a very low temperature of approximately 660°C (or 1120° F) [4] [5]. The Cu element is the most common series element. Its importance directly comes after the elements of gold, silver and platinum. It also has the same FCC crystal structure of Al and it is melted in 1080°C [2] [6].
Combining between the Al and Cu can provide such interesting cast alloys. That is, their cast alloys may have significant mechanical properties such as hardness and high strength, and good machinability [7]. They are used in some important manufacturer such as bus bodies, beverage cans and automotive parts [1]. Al-Cu chain alloys can be utilized for the machine parts, aircraft materials and structural materials. Significant characteristics of high damage tolerance, high strength to weight ratio, cutting properties and good fatigue resistance are resulted [6].
The aim of this paper is preparing cast alloys of impure and pure Al-Cu. Then, testing some important mechanical properties such as hardness. The advantages of this work can be exploited in very critical industries, for instance, manufacturing ships and airplanes.
The remaining sections after the introduction are organized as follows: Section 2 provides the related literature review, Section 3 illustrates the theoretical part of this study, Section 4 demonstrates the practical results and Section 5 clarifies the conclusion.

Related Literature Review
Many studies were presented for the Al-Cu cast alloys.  Non-Isothermal Ageing (NIA) treatment was adopted [7]. In 2020, Soni and Mandloi explained tribological and mechanical properties of artificial age. The Al-Zn-Mg-Cu alloy was concentrated. Various aging temperatures were examined with the precipitation kinetics to enhance the tribological and mechanical characteristics. That is, over aging, optimum aging, under aging and pre aging were used [20]. Also in the same year, Puga illustrated forming and casting of advanced Al alloys. It has been highlighted that the competitiveness and quality of a casting are strongly based on the technique that is used to generate it and quality of the molten alloy. Furthermore, it has been cited that casting the Al alloy is a difficult process as it is prone to heterogeneous and dendritic structures, in addition to the hydrogen absorption during melting [21].
From the literature it can be noticed that many work were applied for Al alloys, as well as, for Cu alloys. However, they are still requiring more investigations. In this paper, comprehensive study is provided for impure and pure Al-Cu cast alloys by establishing many samples and applying effective treatments.

Theoretical Part
In this work, extensive processes are considered, each of which has reasonable theory.  Table 1 shows the prepared weights and ratios for the 6 impure Al and Cu. Whereas, Table 2 provides the employed weights and ratios for the pure Al and Cu.
where: is the HV measurement for N number, P is the load in (Kg), ∅=136º, ∅ =0.927 and is the squared average between the length and width of pressured diamond head.
Furthermore, additional hardness measurements are computed. These are the Hardness Brunel (HB) and Tensile Strength (TS). HB measurement has been collected from the Hardness Conversion Table (HCT) [22]. TS measurement can simply be calculated as follows [22]: where: is the TS measurement for N number and is the H.B measurement for N number.
It is worth mentioning that the eutectic point, two nearest points around it and two far points of hypoeutectoid and hypereutectoid have been considered in this study. The eutectic point is defined as a smallest measured point that refers to easy melt of casted elements. Furthermore, the hypoeutectoid and hypereutectoid points are denoted as the measured points which positioned in locations less and high than the eutectic point, respectively [22].
Finally, outcomes of the employed measurements for established cast alloys are recorded and compared.

Practical Part with Discussions
First of all, multiple Al-Cu cast alloys have been established. In each alloy a Cu was firstly melted under very high temperatures by using a gas furnace. Consequently, the Al was secondly added to the melted Cu in the same gas furnace. So, the Al was gradually melted too. Both were carefully mixed by using a rod of Carbon (C). Then, the mixed liquid was spilled into a mold of steel and concreted. These processes were repeated many times where 13 samples of Al-Cu cast alloys have been created.
The established samples are divided into two main groups (impure and pure). The impure group consists of 7 samples for various Al and Cu percentages of weights (1) . On the other hand, the pure group consists of 6 samples for various Al and Cu percentages of weights too. The prepared weights and ratios for the impure Al and Cu are given in Table 1.
Whilst, the prepared weights and ratios for the pure Al and Cu are given in Table 2.
The created cast alloys have been treated by heating for the 1 st time in order to operate recrystallization, where an electric furnace was used. The established cast alloys were spent an 1 hour at high temperature of 500°C. Subsequently, the electric furnace was turned off and the cast alloys were left inside for around 24 hours. Then, the established cast alloys have been chopped with a R of rubbing that approximately equal to 0.5. Each sample has been carefully covered and labeled. Fig. 3 shows examples of these samples.
Heat treating has been applied for the 2 nd time in order to examine different quenching conditions, where the same electric furnace was utilized. Similar time and temperature treatments (1 hour at 500°C) were employed. The difference between the 1 st and 2 nd times of heat treating is that the 2 nd time did not consider leaving the created cast alloys inside the electric furnace for about 24 hours. However, they are quenched by oil, water or air.
Hence, the hardness has been measured for all the established cast alloys. More specifically, the hardness measurements of HV, HB and TS have been applied. For evaluating the HV, the WOLPERT device of type (V-Testor 2) with P=1Kg and Equation (1) have been exploited. For assessing the HB, the HCT [22] has been utilized. For computing the TS, Equation (2) has been employed. Tables 3 and 4 show the details and measurements of the Al-Cu cast alloys for both impure and pure groups, respectively.
(1) Weight Percentage (wt%) can be converted to Atomic weight Percentage (At%).  First of all, the measured HV, HB and TS values for the impure cast alloys are more fluctuated than the pure cast alloys. This is due to the effects of other embedded elements in the impure cast alloys.
Reasonable outcomes can be observed from Table 3 and Fig. 4. That is, in all samples of the Al-Cu cast alloys impure group for the HV measurements to all quenched conditions, the eutectic point is located in the value when Cu weight is equal to 33%. The hardness Labels Prepared Alloys in this point can be considered as very low in all the measured cases. For the point that is positioned near from the eutectic in the value when Cu weight is equal to 30%, the hardness in this point has attained the highest HV in all the measured cases. Likewise, these results are consistent with other employed measurements of HB and TS as shown in Table 3.
Interested outcomes can be investigated from Table 4 Table 4.
The main difference between the impure and pure performance is that in the impure measurements the eutectic points have achieved low HV, HB and TS evaluations, whilst, in the pure measurements the eutectic points have achieved high HV, HB and TS evaluations. This is reasonable as the performances of impure cast alloys are affected by other embedded elements. The results of pure measurements can be used as standards because no other embedded elements could influence the performances.    Another main issue that is worth to be highlighted is that the impure cast alloys are less affected by the quenched conditions of air, oil and water than the pure cast alloys. This is also expectable because the pure cast alloys are sensible to the quenched conditions. However, the influences of different quenched conditions to the pure cast alloys are slight not significant. With more explanation, the highest measurement value is when Cu weight equal to 33% after quenching by air and it is when Cu weight equal to 35% after quenching by the other conditions (oil and water). This is due to the sensitivity of pure cast alloys to the different quenched conditions, where using air provides slow quenching time than oil and water.
The suggested processing steps in this paper can be considered to be worthy as other suggested processing steps in .

Conclusions
This paper offered a comprehensive study for impure and pure casts of Al and Cu. It consisted of multiple steps, these are: collecting Al and Cu materials, grouping them into impure and pure, changing percentages of mixed Al and Cu weights, establishing multiple Al-Cu cast alloys, treating them by heating inside an electric furnace, chopping the cast alloys, repeating the heat treatments followed by quenching with various conditions (oil, water or air), applying effective measurements (HV, HB and TS) and considering multiple essential points (eutectic point, two nearest points around it and two far points of hypoeutectoid and hypereutectoid), and extensively discussing and comparing the essential outcomes.
First of all, the measured HV, HB and ST values for the pure cast alloys are more smoother than the impure cast alloys. This is because of the influencing of other embedded elements in the impure cast alloys.
The results were attained such promises, reasonable and interesting outcomes. The HV, The contradictory between the performances of impure and pure cast alloys can be explained. The impure cast alloys are influenced by other embedded elements, whereas, the pure cast alloys are not affected by such elements. Moreover, the pure cast alloys are more sensible to the quenched conditions of air, oil and water than the impure cast alloys.