**3.1 Heat treatment**

The processes of heat treatments are performed to dissolve some phases and to generate some new phases. There are different processes and methods to perform heat treatments, which are explained in **Table 1**. The heat treatment processes increase the corrosion resistance and strength of the composites. The heat treatments are classified into the following categories


In solution heat treatments, the casted alloys/composites are heated to a specific temperature for a particular period of time to develop the desired constituent in the matrix. The billets are then quenched suddenly to sustain the phases develop.

Homogenization heat treatments are performed to enhance the workability of cast billets. The brittle nonequilibrium phases are dissolved, and a homogenous microstructure is developed. The homogenization of the billets is performed at the recrystallization temperature of the materials.

Aging is referred to as the process of heat treatment in which precipitates developed during homogenization are decomposed at some elevated temperature. The aging leads


#### **Table 1.**

*Types of heat treatment employed to MMC for microstructure modification.*

#### **Figure 2.**

*Types of plastic deformation used for MMCs.*

to an increase in yield strength and hardness of the alloy/composite. The aging process may be natural (at room temperature) or artificial aging (at elevated temperature).

Some terms have been introduced by the aluminum association for aluminum and its alloys and are explained in **Table 1**.

#### **3.2 Plastic deformation**

The metal matrix composites are deformed into different shapes, and the microstructure is changed to increase the strength of the composites. The

plastic deformation can be categorized into traditional deformation and severe plastic deformation. The deformation could be hot or cold deformation. The shape of the composite is changed, and mechanical properties are moderately enhanced in traditional deformation, but severe plastic deformation alters the microstructure, and mechanical properties are exceptionally increased. The composition of the microstructure is changed, but the shape of the composite remains the same. The type of plastic deformation is given in the following flow chart **Figure 2**.
