**1. Introduction**

Functionally graded materials (FGMs) are a distinct and varied class of materials with a wide range of uses, from home to commercial. The introduction of these materials in the field of mechanical and materials engineering aims to provide a novel and resilient material that satisfies mechanical, microstructural, and tribological requirements. In order to provide solutions with this kind of materials, these types of materials are designed and developed. Materials with continuous material properties in all

directions and some modifications to their microstructure are unable to withstand all temperature variations and gradients within a short period of the material thickness.

Even if they are successful, researchers with their creativity and knowledge are working hard to produce these materials to a greater level, but the production and characterization processes have flaws and limitations. This is frequently accomplished by progressively shifting the volume fraction of two components with various thermomechanical properties in a certain direction, resulting in a compound with various volume ratios [1]. For spacecraft with one side exposed to extremely high temperatures and the other exposed to extremely low temperatures, FGMs are the best choice because they distribute material functions throughout the material body for best heat resistance and mechanical qualities. FGM is used in the development of most industrial sectors' products today, including those in the automotive, information technology, computer science, and other related fields [2].

### **1.1 Development and progression of FGM**

Most of the research investigations are progressed with the development of functionally graded aluminum composites by the aid of centrifugal casting analyzed the influence of mechanical and wear properties of pure aluminum, boron carbide, silicon carbide, alumina, and titanium boride. Radhika et al. [3] in her research experimentations with FGM stated that the outer peripheries of the FGM exhibit higher hardness except in AlB4C and the outer zone exhibits tensile strength at its maximum. Chandrappa et al. [4] have synthesized with the aid of conventional powder metallurgy method at 436<sup>o</sup> C sintering temperature and depicted that high volume fraction of SiC caused clustering of carbide phase at grain boundaries, which restricts interparticle contacts and further becomes a wall for densification in their study titled, "manufacturing and characterization of Al-SiC FGM developed through powder metallurgy." For preparation of Al/Si functionally graded materials using ultrasonic separation method, Zhang Zhong tao et al. [5, 6] have successfully synthesized the standardized Al-SiC FGM and also depicted that increasing the composition of SiC makes the FGM harder and at a limiting value, it becomes brittle and crack formation is observed, with the highest compressive strength obtained at 7.5% of SiC insertion.

A research article designated as synthesis of hydroxyapatite in combination with titanium alloy to prepare FGM composites by powder methodology ultimately used as implant materials depicted that microhardness is increased by 28% when compared with steel alloys. Amir Arifin et al. [7] successfully processed HA/Ti FGMs and depicted that increasing the titanium percentage increases the hardness and compaction capability of the synthesized FGM. He has also illustrated the elements' flawless cohesion and excellent microstructural characteristics. Madhusudan et al. [8] successfully formulated a procedure to determine the optimal thickness of the mold material in the production of FGM in centrifugal casting, as well as inferred various parameters affecting FGM production, starting with preheating, molten metal heating, and solidification rate.
