**5. Fabrications methods**

The development of fabrication processes for the production of high-performance composites has been reported in many research studies [22]. **Figure 5** illustrates various fabrication techniques that were in use for the last few years. The following methods are most common for fabrication of the MMCs at large-scale industrial level.

**Figure 5.** *Different fabrication method of composite cutting tool.*

In the past decade, there has been a research done on the fabrication of MMCs with the different proportions of reinforcement for obtaining the required properties.

Liquid-state processing is defined as the incorporation of reinforcement in the matrix in molten form to prepare metal matrix composite. The various advantages of liquid-state processing are:

• Faster processing rate, especially when dealing with low melting point alloys of aluminum and magnesium. It can also produce near net shape of the final component in a single step.

Liquid-state processing of metal matrix composites involves incorporating or combining a liquid metal matrix with the reinforcement. The most common liquidphase processing techniques can be subdivided into four major categories:


Solid-state processing is preferred because of the following drawbacks in the liquid-state processing:


The most common solid-phase processes are based on powder metallurgy techniques, which generally use discontinuous reinforcements such as flakes/particulates/ short fibers, since it is easy to do the mixing and blend with it and much more effective to reduce the porosity [23]. During the process, the ceramic and metal powders are mixed, are statically cold compacted, sintered, and hot pressed to get higher densification or it may be mixed and blended followed by direct hot isostatic pressing to achieve the full density. Further secondary processing such as extrusion, forging etc., might be required to achieve the final shape of the component.

In-situ processing involves chemical reactions that result in the creation of a reinforcing phase within a metal matrix. The reinforcements can be formed from the precipitation in liquid or solid. This method provides thermodynamic compatibility at the matrix reinforcement interface. The reinforcement surfaces are also likely to be free of contamination and, therefore, a stronger matrix-dispersion bond can be achieved. Different researchers reported the benefits of using these techniques such as lower processing time, temperature as well as the capabilities of producing near net shape, high densification rate and less energy required.
