# Wire Electrical Discharge Machining Characteristics of Al-4.4 Mg-0.7 Mn-0.15 Cr-12 wt.% MoO3 Composites Using Taguchi Technique

Authors: M. Meignanamoorthy; T. Anandaraj; M. Ravichandran; V. Mohanavel; S. Sathish; S.M. Sivagami; Wadi B Alonazi; Sami Al Obaid; Saleh Alfarraj; Kaliannan Durairaj; Manikandan Ganesan
Journal: Advances in Materials Science and Engineering
 (2022)

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## Abstract

This research put forth an effort to produce AA5083 (Al-4.4 Mg-0.7 Mn-0.15 Cr)-12 wt.% MoO3 composite via the stir casting (SC) process, and the effects of process parameters such as pulse on time (TON), pulse off time (TOFF), and current (I) on the wire electrical discharge machining (WEDM) characteristics such as metal removal rate (MRR) and surface roughness (SR) were investigated using the Taguchi method. Numerous unconventional machining methods are accessible to machine MMCs; among that, WEDM is a significant method. ANOVA was utilized to identify the suitable parameters to obtain maximum MRR and least SR. From the analysis, it is clear that TON 120 (μs), TOFF 50 (μs), and I 3 (A) are the noteworthy parameters to acquire maximum MRR and TON 100 (μs), TOFF 40 (μs), and I 3 (A) are the noteworthy parameters to acquire least SR. ANOVA results for MRR showed that TOFF is the extreme inducing factor with the percentage contribution of 27.92% tracked by TON and I with the percentage contribution of 12.09% and 5.07%, respectively. ANOVA results for SR showed that TOFF is the extreme inducing factor with the percentage contribution of 60.33% tracked by TOFF and I with the percentage contribution of 12.31% and 0.33%, respectively.


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## Body

## 1. Introduction

Composite materials exhibit better strength, good toughness, less weight, wear opposition resistance, and less cost. It has already proven its worth as a lighter-weight material for a few years, but the current challenge is to construct it in the cheapest way possible [1]. Metal matrix composites (MMCs) are a collection of materials with perception for a wide range of usages in the structural field. The properties such as lightweight, excellent strength, and opposition to wear are needed for aeronautics and automotive sectors. MMCs are widely utilized in automotive usages such as brake parts, cylinder liners, pistons, bearing surfaces, and camshafts and aeronautics usages such as aircraft structure (major body), exhaust systems, wing and fuselage, and inner aerospace engine parts [2]. MMCs consist of a matrix as metals with some particulates as reinforcements. Despite its excellent strength, stiffness, and wear opposition, MMCs have gained rising notice in numerous engineering fields [3]. Traditional MMCs strengthened with particulates could attain good strength and improved elastic modulus with higher reinforcement content, when the ductility and toughness fall radically with the rise in the range of reinforcements because of the usual transaction amid strength and ductility [4]. Nowadays, aluminum alloy found numerous applications in Space Shuttle and automotive and aeronautics structures due to its effortlessness of operation and sensibly better mechanical properties. The untainted aluminum alloy properties may be improved by combining the utmost generally utilized particulate reinforcements [5]. Aluminum matrix composites (AMCs) are widely used in the engineering field despite their extraordinary mechanical and tribological behaviour. This leads to the growth of AMCs with each probable aluminum alloy as matrix strengthened with numerous reinforcements to attain the explicitly needed properties [6]. AMCs are lightweight materials accompanied by better electrical and thermal conductivity and good stiffness, hardness, strength, and wear opposition. Because of high fabrication costs, AMCs are deployed solitarily for armour weapons and aeronautics applications. AMCs have additional usages in automotive parts such as engine cylinder liners, disk brakes, drum brakes, and pistons [7]. Molybdenum trioxide (MoO3) strengthens AMCs which has higher mechanical properties [8]. Concurrently due to bigger self-lubricating contact, MoO3 improves the composite wear opposition [9]. MoO3 has arriving widespread deliberation as a potential reinforcement for MMCs to enhance the properties [10]. Stir casting (SC) is an inexpensive method for the production of AMCs [11]. Through the SC process, fine dispersal of reinforcement with matrix could be possible [12]. SC method was extremely concerned to improve the mechanical behaviour and reinforcement of various alloy materials for strengthening of harder particles [13]. Traditional machining methods such as turning and milling are not appropriate for machining composite materials. The presence of hard abrasive and ceramic materials causes tool wear and breakage [14]. Therefore, nontraditional machining process such as WEDM is utilized to machine the composite material [15]. Machining of the smallest hole is not possible in all the nontraditional machining, but it is possible in WEDM [16]. WEDM is a feasible choice for cutting all kinds of materials, which are impossible to cut and somewhat their proposed usages need the shape of complicated profiles [17]. Furthermore, fewer burr arrangements and no residual stresses amid WEDM are the additional merits that extra emphasize its pre-eminence. With reverence to the machine utilized for performing WEDM, two variants are accessible: (i) less speed and (ii) rapid cutting machine [18]. In WEDM, the outside layer of the work material is eradicated by means of a series of sparks created amid the workpiece and electrode. The workpiece and electrode are set aside individually and are completely engrossed in dielectric fluid [19]. When machining via WEDM, electrical conductivity is the main issue for machining materials [20]. Titus et al. [21] studied the influence of WEDM process parameter on Cu-BN composites, found the optimal parameters by Taguchi grey relational analysis, and concluded that pulse ON and BN volume fraction were the major noteworthy parameters to acquire maximum MRR and pulse ON and pulse OFF were the major noteworthy parameters to acquire least SR. Padhi et al. [22] studied the suitable parameters for WEDM of EN-31 using a weighted sum genetic algorithm process to achieve optimum results. Agarwal et al. [23] explored the WEDM characteristics of Ni-27 Cu-3.15 Al-2 Fe-1.5 Mn super alloy and stated that pulse on time has a direct influence on CR while the pulse off time has an opposite influence. Rakesh et al. [24] analyzed the WEDM behavior of MWCNTs and concluded that the inclusion of MWCNTs significantly enhances the machining performance by increasing MRR and concurrently reducing the SR.From the detailed literature, it has been understood that very few research work has been done by using MoO3 as reinforcement with aluminum matrix. Hence, this research work made an effort to develop and study the WEDM behavior of Al-4.4 Mg-0.7 Mn-0.15 Cr-12 wt.% MoO3.


## 2. Materials and Method

The matrix material utilized was AA5083 and MoO3 was used as reinforcement. The percentage of alloying elements in AA5083 is Si: 0.4, Fe: 0.4, Cu: 0.1 wt, Mn: 1.0, Mg: 4.9, Zn: 0.25, Ti: 0.15, Cr: 0.25, and Al balance. The essential amount of AA5083 and MoO3 powders was dignified by an automatic weigh measurement device. By utilizing a crucible furnace, AA5083 was liquefied at 800°C [25]. MoO3 powders were heated at 400°C. Then, to attain the liquid stage, 12 wt.%, MoO3 powder was included in the AA5083 matrix. The mixing was done at 30,000 rps speed for 300 seconds [26]. Amid mixing, least amount of Mg was included to increase wettability. In the end, the liquid metal was bestowed into a die to attain required sizes. The dimensions of the workpiece are 8 × 8 × 30 mm. The WEDM procedure was conducted on AA5083-12 wt.% MoO3 composite via ECOCUT WEDM. Figure 1 displays the machined sample image. The three-level process parameters, namely, TON, TOFF, and I were selected as variables to investigate their influences on MRR and SR. The dimension of samples to carry out the WEDM process was 8 × 8 × 30 mm. The WEDM performance standards chosen for this investigation were MRR and SR. MRR was calculated via weight difference of workpiece before and after the WEDM process by using the following formula: MRR=Wa−Wb/t, where Wa and Wb are the weights of the workpiece before and after the WEDM process and “t” is the machining time in minutes. The SR measurement on the machined surface was done via Mitutoyo surftest SJ-210.Figure 1
Wire electrical discharge machined AA5083-MoO3 sample.


## 3. Results and Discussion

The effect of EDM parameters on SR and MRR was studied via the Taguchi method. The TON, TOFF, and I were selected as parameters, and MRR and SR were considered as output. The parameters and levels are enumerated in Table 1 and experimental trials performed via L9 orthogonal array are enumerated in Table 2. Table 3 displays the responses and the calculated SN ratio of designed experiments. More ANOVA tests were utilized to predict the appropriate parameters.Table 1
Parameters and levels.
S. noTON (μs)TOFF (μs)I (A)110040321205063140609Table 2
L16 orthogonal array experimental results.
Trial no.TON (μs)TOFF (μs)I (A)MRR (g/min)SR (μm)11004030.0431.36421005060.1693.62131006090.0753.373410070120.1043.8151204060.0282.44761205030.1943.614712060120.1783.46881207090.1352.26891404090.1621.9081014050120.0692.669111406030.1293.224121407060.0191.9161316040120.0421.853141605090.1073.831151606060.1263.434161607030.0553.518Table 3
Mean of SN ratios for the MRR and SR.
MRRLevelTON (μs)TOFF (μs)I (A)1−21.23−25.43−21.142−19.42−18.08−24.733−22.81−18.32−18.784−22.53−24.17−21.35Delta3.397.355.95Rank312SRLevelTON (μs)TOFF (μs)I (A)1−9.013−5.360−8.7372−9.212−10.632−8.8283−7.489−10.561−8.7384−9.666−8.826−9.076Delta2.1785.2730.339Rank213


### 3.1. SN Ratio Analysis for MRR and SR

The appropriate process parameter is needed to attain maximum MRR and SR. SN ratio was designed for enlargement quality characteristics of output responses. The mean SN ratios for MRR and SR are displayed in Table3. Figures 2 and 3 display the main effect plot for SN ratios for MRR and SR. The higher MRR is achieved at TON 120 μs, TOFF 50 μs, and I 3 A. From the results, it is clear that TOFF is the noteworthy parameter to attain maximum MRR. The least SR is achieved at TON 100 μs, TOFF 50 μs, and I 3 A. From the results, it is clear that TOFF is the noteworthy parameter to attain the least SR. Current is the most influencing parameter for MRR, and for SR, it does not have much impact.Figure 2
Means of SN ratio for MRR.Figure 3
Means of SN ratio for SR.


### 3.2. Contour Plot Analysis for MRR

Figure4 displays the contour plots for the MRR with respect to (a) pulse off time vs. pulse on time, (b) current vs. pulse on time, and (c) current vs. pulse off time. Contour plots were generated to analyze the influence of process parameters. These contour plots can also provide more evaluation of the association amid the process parameters and response. The contour plots for MRR with respect to selected input machining parameters are displayed in Figures 4 and 5. In Figure 4(a), the dotted zone displays the MRR rate while the pulse off time and pulse on time interrelate each other. It can be understood that the pulse off time is higher for entire values of pulse on time and the higher MRR could be attained. Figure 4(b) displays the contact of current with pulse on time for the MRR. It can be clear that the current is less and the pulse on time is in maximum. Unless current is maximum, least pulse on time is adequate to attain maximum MRR. Figure 4(c) displays the contact of current and pulse off time for the MRR. Although considering the pulse off time and current, the maximum pulse off time is vital to obtain higher MRR.Figure 4
(a). Contour plot for MRR TOFF vs. TON. (b) Contour plot for MRR I vs. TON. (c) Contour plot for MRR I vs. TOFF.
(a)(b)(c)Figure 5
(a) Contour plot for SRI vs. TOFF. (b) Contour plot for SR I vs. TON. (c) Contour plot for SR TOFF vs. TON.
(a)(b)(c)The contour plot for the SR is displayed in Figure5 with respect to (a) I vs. TOFF, (b) I vs. TON, and (c) TOFF vs. TON. Figure 5(a) displays the least SR while the current is in low level. Figure 5(b) displays the interface of current with pulse on time for the SR. It can be clear that if the pulse on time is less, the least SR could be attained. Figure 5(c) displays the contact of pulse off time and pulse on time for the SR. The least pulse off time and pulse on time resulted in the least SR.


### 3.3. ANOVA for MRR and SR

In this investigation, ANOVA was utilized to find the percentage contribution of parameters TON, TOFF, and I on MRR of AA5083-MoO3 composites. Table 4 displays the ANOVA result of MRR. It could be clearly understood that TOFF is the utmost impelling factor with the percentage contribution of 27.92% tracked by TON and I with the percentage contribution of 12.09% and 5.07%, respectively. I is the insignificant parameter with the percentage contribution of 5.07%. The R2 value for the material removal rate is 45.10%. Figure 6(a) displays the normal probability plot of MRR and it was obvious that all the residuals were found to be normally distributed beside the straight line at 95% confidence level.Table 4
Results of ANOVA for MRR.
SourceDFAdj SSAdj MSF-valueP valuePercentage contributionTON (μs)20.0058350.0019450.440.73212.09TOFF (μs)20.0134680.0044891.020.44827.92I (A)20.0024470.0008160.180.9035.07Error20.0264740.004412Total80.048224S = 0.0664252; R-Sq = 45.10%; R-Sq(adj) = 0.00%.Figure 6
(a) Probability plot for MRR. (b) Probability plot for SR.
(a)(b)In this investigation, ANOVA was utilized to find the percentage contribution of parameters TON, TOFF, and I on SR of AA5083-MoO3 composites. Table 5 displays the ANOVA result of SR. It could be clearly understood that TOFF is the utmost impelling factor with the percentage contribution of 60.33% tracked by TOFF and I with the percentage contribution of 12.31% and 0.33%, respectively. I is the insignificant parameter with the percentage contribution of 0.33%. The R2 value for the material removal rate is 72.98%. Figure 6(b) displays the normal probability plot of SR and it was obvious that all the residuals were found to be normally distributed beside the straight line at 95% confidence level.Table 5
Results of ANOVA for SR.
SourceDFAdj SSAdj MSF-valueP valuePercentage contributionTON (μs)31.24470.41490.910.48912.31TOFF (μs)36.09882.03294.470.05760.33I (A)30.03360.01120.020.9940.33Error62.73120.4552Total1510.1083S = 0.674690; R-Sq = 72.98%; R-Sq(adj) = 32.45%.


### 3.4. Interaction Plot Analysis for MRR and SR

Figures7(a) and 7(b) display the interaction plots for the MRR and SR. The interaction amid TON, TOFF, and I with MRR is displayed in Figure 7(a). From the graph, it could be understood that when TOFF enhances, MRR also increases. The maximum MRR was observed for TOFF. The maximum MRR was obtained for the parameters TON 120 (μs), TOFF 50 (μs), and I 3 (A). When TON and I interact, the increase of these parameters enhances the MRR, and TOFF plays a major role in influencing the MRR. The interaction of TON with I obviously shows this. TON does not have significance in MRR. The interaction amid TON, TOFF, and I reveals that TON is an unimportant factor for MRR.Figure 7
(a) Interaction plot for MRR. (b) Interaction plot for SR.
(a)(b)The interaction amid TON, TOFF, and I with SR is displayed in Figure 7(b). From the graph, it could be understood that when TOFF increases, SR reduces. The least SR was observed for TOFF. TON 100 (μs), TOFF 40 (μs), and I 3 (A) are the noteworthy parameters to acquire the least SR. When TON and I interact, the increase of these parameters reduces the SR, and TOFF plays a major role in influencing the SR. The interaction of TON with I obviously shows this. I does not have significance in SR. The interaction amid TON, TOFF, and I reveals that I is an unimportant factor for SR.


## 3.1. SN Ratio Analysis for MRR and SR

The appropriate process parameter is needed to attain maximum MRR and SR. SN ratio was designed for enlargement quality characteristics of output responses. The mean SN ratios for MRR and SR are displayed in Table3. Figures 2 and 3 display the main effect plot for SN ratios for MRR and SR. The higher MRR is achieved at TON 120 μs, TOFF 50 μs, and I 3 A. From the results, it is clear that TOFF is the noteworthy parameter to attain maximum MRR. The least SR is achieved at TON 100 μs, TOFF 50 μs, and I 3 A. From the results, it is clear that TOFF is the noteworthy parameter to attain the least SR. Current is the most influencing parameter for MRR, and for SR, it does not have much impact.Figure 2
Means of SN ratio for MRR.Figure 3
Means of SN ratio for SR.


## 3.2. Contour Plot Analysis for MRR

Figure4 displays the contour plots for the MRR with respect to (a) pulse off time vs. pulse on time, (b) current vs. pulse on time, and (c) current vs. pulse off time. Contour plots were generated to analyze the influence of process parameters. These contour plots can also provide more evaluation of the association amid the process parameters and response. The contour plots for MRR with respect to selected input machining parameters are displayed in Figures 4 and 5. In Figure 4(a), the dotted zone displays the MRR rate while the pulse off time and pulse on time interrelate each other. It can be understood that the pulse off time is higher for entire values of pulse on time and the higher MRR could be attained. Figure 4(b) displays the contact of current with pulse on time for the MRR. It can be clear that the current is less and the pulse on time is in maximum. Unless current is maximum, least pulse on time is adequate to attain maximum MRR. Figure 4(c) displays the contact of current and pulse off time for the MRR. Although considering the pulse off time and current, the maximum pulse off time is vital to obtain higher MRR.Figure 4
(a). Contour plot for MRR TOFF vs. TON. (b) Contour plot for MRR I vs. TON. (c) Contour plot for MRR I vs. TOFF.
(a)(b)(c)Figure 5
(a) Contour plot for SRI vs. TOFF. (b) Contour plot for SR I vs. TON. (c) Contour plot for SR TOFF vs. TON.
(a)(b)(c)The contour plot for the SR is displayed in Figure5 with respect to (a) I vs. TOFF, (b) I vs. TON, and (c) TOFF vs. TON. Figure 5(a) displays the least SR while the current is in low level. Figure 5(b) displays the interface of current with pulse on time for the SR. It can be clear that if the pulse on time is less, the least SR could be attained. Figure 5(c) displays the contact of pulse off time and pulse on time for the SR. The least pulse off time and pulse on time resulted in the least SR.


## 3.3. ANOVA for MRR and SR

In this investigation, ANOVA was utilized to find the percentage contribution of parameters TON, TOFF, and I on MRR of AA5083-MoO3 composites. Table 4 displays the ANOVA result of MRR. It could be clearly understood that TOFF is the utmost impelling factor with the percentage contribution of 27.92% tracked by TON and I with the percentage contribution of 12.09% and 5.07%, respectively. I is the insignificant parameter with the percentage contribution of 5.07%. The R2 value for the material removal rate is 45.10%. Figure 6(a) displays the normal probability plot of MRR and it was obvious that all the residuals were found to be normally distributed beside the straight line at 95% confidence level.Table 4
Results of ANOVA for MRR.
SourceDFAdj SSAdj MSF-valueP valuePercentage contributionTON (μs)20.0058350.0019450.440.73212.09TOFF (μs)20.0134680.0044891.020.44827.92I (A)20.0024470.0008160.180.9035.07Error20.0264740.004412Total80.048224S = 0.0664252; R-Sq = 45.10%; R-Sq(adj) = 0.00%.Figure 6
(a) Probability plot for MRR. (b) Probability plot for SR.
(a)(b)In this investigation, ANOVA was utilized to find the percentage contribution of parameters TON, TOFF, and I on SR of AA5083-MoO3 composites. Table 5 displays the ANOVA result of SR. It could be clearly understood that TOFF is the utmost impelling factor with the percentage contribution of 60.33% tracked by TOFF and I with the percentage contribution of 12.31% and 0.33%, respectively. I is the insignificant parameter with the percentage contribution of 0.33%. The R2 value for the material removal rate is 72.98%. Figure 6(b) displays the normal probability plot of SR and it was obvious that all the residuals were found to be normally distributed beside the straight line at 95% confidence level.Table 5
Results of ANOVA for SR.
SourceDFAdj SSAdj MSF-valueP valuePercentage contributionTON (μs)31.24470.41490.910.48912.31TOFF (μs)36.09882.03294.470.05760.33I (A)30.03360.01120.020.9940.33Error62.73120.4552Total1510.1083S = 0.674690; R-Sq = 72.98%; R-Sq(adj) = 32.45%.


## 3.4. Interaction Plot Analysis for MRR and SR

Figures7(a) and 7(b) display the interaction plots for the MRR and SR. The interaction amid TON, TOFF, and I with MRR is displayed in Figure 7(a). From the graph, it could be understood that when TOFF enhances, MRR also increases. The maximum MRR was observed for TOFF. The maximum MRR was obtained for the parameters TON 120 (μs), TOFF 50 (μs), and I 3 (A). When TON and I interact, the increase of these parameters enhances the MRR, and TOFF plays a major role in influencing the MRR. The interaction of TON with I obviously shows this. TON does not have significance in MRR. The interaction amid TON, TOFF, and I reveals that TON is an unimportant factor for MRR.Figure 7
(a) Interaction plot for MRR. (b) Interaction plot for SR.
(a)(b)The interaction amid TON, TOFF, and I with SR is displayed in Figure 7(b). From the graph, it could be understood that when TOFF increases, SR reduces. The least SR was observed for TOFF. TON 100 (μs), TOFF 40 (μs), and I 3 (A) are the noteworthy parameters to acquire the least SR. When TON and I interact, the increase of these parameters reduces the SR, and TOFF plays a major role in influencing the SR. The interaction of TON with I obviously shows this. I does not have significance in SR. The interaction amid TON, TOFF, and I reveals that I is an unimportant factor for SR.


## 4. Conclusion

(i)
AA5083-12 wt.% MoO3 composites were produced via SC process and the influence of process parameters on WEDM characteristics was investigated using the Taguchi method(ii)
Taguchi method is a suitable tool to identify the optimal process parameters to attain maximum MRR and SR in the WEDM process(iii)
The higher MRR was acquired for the parameters TON 120 (μs), TOFF 50 (μs), and I 3 (A)(iv)
The least SR was acquired for the parameters TON 100 (μs), TOFF 40 (μs), and I 3 (A)(v)
For MRR, the ANOVA results exposed that TOFF is the utmost impelling factor with the percentage contribution of 27.92% tracked by TON and I with the percentage contribution of 12.09% and 5.07%, respectively(vi)
For SR, the TOFF is the utmost impelling factor with the percentage contribution of 60.33% tracked by TOFF and I with the percentage contribution of 12.31% and 0.33%, respectively(vii)
From the obtained results, it is clearly understood that the developed AA5083-12 wt.% MoO3 composites can replace the existing material in the field of aerospace and automobile sectors



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