Al7129 Metal matrix enhanced with Titanium carbide (TiC) and Boron carbide(B 4 C) optimized machining parameters utilizing Taguchi method for Surface roughness

The influence of spindle speed, feed rate, and depth of cut of alumina particle on lowering surface roughness during turning of Al7129/TiC/B 4 C hybrid composite is investigated in this study. The composite is turned using a TiN coated solid carbide tool. Taguchi's experimental design concept is utilized to optimize three tiers of design parameters for improved for better surface finish. The results of the experiments and the microstructure of the machined surface demonstrate that the samples with the lowest feed rate perform better in terms of surface roughness. Surface roughness is also influenced by the wt% of alumina, which is followed by spindle speed when spinning the produced samples.


Introduction
Aluminum matrix composite (AMC) is a relatively new material that has a wide range of uses due to its quantifiable benefits. In many engineering domains, they are employed in a variety of structural, non-structural, and functional applications. In recent years, the particulate reinforced AMCs are replacing the conventional materials that are used in aircraft and automotive components. The most common applications are aircraft's engine cowlings, landing gear doors, automotive pistons, bearings, etc. In those major applications, the manufactured components are expected to be with good surface finish and accuracy. Particulate reinforced Aluminium (Al) based composite are found very difficult in machining due to the presence of hard ceramic oxide reinforcement. Turning is one of the most prevalent machining operations related with the manufacturing process. In practise, producing machined with a decent surface quality has proven to be extremely challenging. As a result, minimising surface roughness in turning parts is difficult and must be managed.The hard ceramic particles in the matrix, such as Al2O3/SiC, make it difficult to machine, which affects the surface finish by increasing the composite's surface roughness. In such circumstances, adding graphite to the matrices minimises tool wear during milling and improves the composite's surface polish. [1]. Most of the studies on Metal matrix composite (MMC) are focused on the study of tool wear characteristics during machining of aluminium alloy composite. The surface finish of the component can be varied along the process parameters such as spindle speed, feed etc.The present work is focused on minimizing surface roughness in turning of Al7129/TiC/B4C hybrid composite. From the various literatures available, it has been observed that feed rate, cutting speed and wt % of the reinforcements are key factors influencing surface roughness. Palanikumar and Karthikeyan [2] made an attempt on assessing the factors influencing surface roughness on machining of Al/SiC particulate composite. They have used K 10 tungsten carbide tool inserts for machining. The machining parameters considered were % vol fraction of SiC, cutting speed, depth of cut and feed rate. They employed ANOVA technique to optimize the machining parameters. Saravanakumar and Sasikumar [3] made a study on prediction of surface roughness in turning using design of experiments. They concluded that selection of reinforcements plays an important role in improving the material properties and machinability of the composite. Considering two levels of factors, they had developed a mathematical model for the proposed cutting parametersIt contributes to the product's durability. The Taguchi method is used in a very short period of time and with minimal effort. As a result, Taguchi's method is being used in a variety of industries to improve process quality in the manufacturing sector.Surface roughness and cutting force are both critical parameters in the machining process. [4][5][6][7][8]. Cutting force is required for power machining calculations. Cutting forces have an impact on dimensional accuracy, workpiece deformation, and chip formation.In industries, components with a specific surface roughness are always required based on the needs of the customer. This can be accomplished through the optimization process.d that the quality of the drilled holes can be improved by proper selection of cutting parameters.In the present study, an attempt has been made to optimize the machining parameters for better surface roughness in turning of Al7129/TiC/B4C hybrid composite. [9][10][11][12][13][14].

Experimental methods 2.1. Materials and methods
For the present work, Turning of Aluminium 7129 (Al7129) has been used as matrix phase and Titanium carbide (TiC) and Boran carbide (B4C) powder as reinforcement phase. Al 7129 has been chosen as the matrix material due to its lower strength and better machinability performance. In order to increase the strength of the matrix Al2O3 particles are added as the reinforcements where as particlesTiC& B4C addition improves the machiniablity. The chemical composition of the base metal and its physical properties are shown in Tables 1 & 2 respectively While the chemical  compositions  and  physical  properties  reinforcement are shown in Tables 3 & 4 respectively. Al2O3 provides good wettability between the matrix and reinforcements particles acts as a solid lubricator which helps in easy machining of the composite.The composite have been fabricated using stir casting technique at an optimal speed to ensure even distribution of the reinforcements along the matrix. The composite is fabricated at three different compositions taking as 3-9 wt% in steps of 3 wt% to the matrix material. The machined composite are tested for surface roughness using Handy Surf surface roughness measuring device of E-DT5706 which consists of a probe connected to it. Figure 1 shows used and the surface roughness measuring device.

Taguchi method
Taguchi's experimental design is used to reduce quality loss by using the three possibilities provided in Taguchi's design analysis, according to a lot of research. The terms "the-nominal-the-best," "the-larger-the-better," and "the-smaller-the-better" are used to describe them. The concept of taguchi method is to find out the best combination of design parameters by conducting minimum number of experiments. As a result, it provides main effects and interaction effects which uses S/N ratio to quantify the data variation. For the present analysis, the machining parameters have to be optimized for minimum surface roughness. Therefore, "thesmaller-the-better" concept is chosen using the equation, Where, "n" is the number of replications of experiment and "y" is the quality score with smaller-the-bettervalueofexperimentaldata"i". Statistical software Minitab18 is used for the analysis and the results arrived are "main effects" and responsetable for the variables. The impacts of the design parameters and levels on the response variables are depicted in the main graphs for S/N ratio. The optimal factor levels are those that optimise the proper S/N ratio. At the greatest spindle speed (250 rpm), lowest feed rate (25 mm/min), and wt of alumina, a superior surface finish. The surface roughness of the composite increases with increasing feed rate and decreases with spindle speed, according to the findings. When the feed rate is increased, the tool's load is increased, which increases cutting force, resulting in a poor surface finish. At all situations, a similar effect was observed in reduced spindle speed. It shows for S/N ratio in which it is clearly visible that feed is the most influencing factor since it is ranked first followed by alumina and spindle speed in minimizing the surface roughness.

Analysis of variance (ANOVA)
Analysis of variance can be used to investigate and model the relationship between a response variable and independent variables. The link between a response variable and independent factors can be investigated and modelled using analysis of variance. With the help of the P-value, it was also possible to check the elements that are statistically significant at a 95% confidence level. The higher level of significance is indicated by a P-value of less than or equal to 0.05.

Confirmation tests
A confirmation tests has to be carried out at the optimal level of parameters. The parametric combinations obtained for minimum surface roughness was obtained as 250 rpm (spindle speed), 25 mm/min (feed rate), 6% (wt of alumina).

Conclusions
Using Taguchi's experimental design, the process parameter that has an impact on surface roughness during machining Al7129/TiC/B4C hybrid composite is optimized in this study. The experimental out comes drawn are: i.As the speed and feed rate are raised, the surface roughness of the rotating work piece reduces. ii. ii. It is visible from the major impacts plot for S/N ratio that 6 wt% alumina has a superior surface finish than other alumina compositions.
iii. According to the S/N ratio response table, feed rate is the most important element in lowering surface roughness during machining of Al7129/TiC/B4C hybrid composite, followed by wt% alumina and spindle speed. iv. The optimal parametric conditions obtained for minimizing surface roughness are at highest spindle speed of 250 rpm, lowest feed rate 25 mm/min, 6wt % of Al2O3. v. The microstructure of the machined samples clearly reveals that the 6% Al2O3 composition shows less deformation during machining when compared to other samples.

95% CI for the Mean
The pooled standard deviation is used to calculate the intervals.