**5.4 Scanning electron microscopy (SEM)**

The scanning electron microscopy (SEM) characterization shows the development of grains and grain limits of grid and building up materials, and there are no arrangement of voids, breaks, and surface flaws [10]. This process is done as per ASTM E986, which clearly shows how the bonding of constituents and blunt interfaces with good

*Experimentation and Optimization of Multilayered Aluminum-Based Functionally Graded… DOI: http://dx.doi.org/10.5772/intechopen.107284*

#### **Figure 8.**

*Compression strength vs. composition.*

#### **Figure 9.**

*Microhardness vs. composition.*


#### **Table 3.**

*Depiction of compressive strength of FGM composites with composition.*

amount of contact between them. The observation of bonding is not only done at the bonding region of the matrix and the reinforcement's level but also we have observed at the intermolecular level, that is, at the middle region where the matrix and the reinforcements bond together with the equal weight percentages (50%) as depicted in **Figures 10**–**12**.


#### **Table 4.**

*Microhardness results by Vickers hardness tester.*

#### **Figure 10.**

*SEM micrographs of Al356/0.6SiCnp/0.6Ni FGM. (a) Al356/0.05Ninp/0.05CrnpHybrid nano metal matrix composite (HNMMC). (b) Al356/0.1Ninp/0.1CrnpHybrid nano metal matrix composite (HNMMC).*

#### **Figure 11.**

*EDAX micrographs of Al356/0.6SiCnp/0.6Ni FGM.*

*Experimentation and Optimization of Multilayered Aluminum-Based Functionally Graded… DOI: http://dx.doi.org/10.5772/intechopen.107284*

#### **Figure 12.**

*SEM micrographs, quantitative results, and mapping of Al6061/0.6SiCnp/0.4Crnp.*

**Figure 13.**

*EDAX Analysis of Al-SiC-Ni FGM bottom most layer.*

#### **5.5 Energy-dispersive X-ray analysis (EDAX)**

The energy-dispersive X-ray analysis (EDAX) shows that there is no presence of any foreign material in the microstructure of the final developed material and also there are no traces of chemical reaction within the elements and nonexistence of carbides and oxides [11, 12] as shown in **Figures 13** and **14**.

#### **5.6 X-ray diffraction analysis (XRD)**

The X-ray diffraction analysis (XRD) analysis is exclusively done to determine the grain size, and it is found to be 6.28 Å and the calculated maximum interplanar spacing of the atoms is 3.13 Å [13, 14]. **Table 5** clearly visualizes the effect of the diffraction angle and the full width at half maximum (FWHM) parameter on the crystalline size,

#### **Figure 14.**

*EDAX test results for bottom layer of Al-SiC-Ni FGM.*


#### **Table 5.**

*XRD values of the dry compacted FGM specimens.*

thereby emphasizing the bonding strength between the matrix and the reinforcement constituents and also the size of the ultimate molecules formed after powder metallurgical process [15–17](**Figure 15**).

#### **5.7 Optimization of the process parameters**

Taguchi optimization is used to discover the best fabrication conditions for achieving the best microhardness and compressive strength. We employed the larger is better condition (1) of Taguchi optimization, since the material required great hardness and compacting strength in 95% of the applications [18–21]:

$$\text{Larger is } Better = -10\log\_{10}\left[\left(\frac{1}{n}\right)\*\Sigma\left(\frac{1}{\mathcal{Y}\_i^2}\right)\right] \tag{1}$$

The SN (signal-to-noise) ratios for compressive strength measurements are generated based on the aforesaid equation, and the values are utilized to plot

*Experimentation and Optimization of Multilayered Aluminum-Based Functionally Graded… DOI: http://dx.doi.org/10.5772/intechopen.107284*

#### **Figure 15.** *XRD graph of Al-Sic-Ni FGM.*

the curves, which are shown in **Figure 16**. **Figure 16** shows the SN ratio plots for compressive strength, which shows the effect of each parameter utilized in manufacturing and blend production of the dry-compacted specimens [22–24]. High compressive strength was achieved by using parameters such as compacting pressure, sintering pressure, and sintering duration. When compared with compacting pressure and sintering time, sintering temperature causes high deviations in compressive strength, but sintering duration improves compressive strength as depicted in **Tables 6** and 7 and **Figure 17** [25–27].
