**1.2 Metals and alloys**

Metals are the class of materials characterised by their high electrical conductivity as well by thermal conductivity. Metals are crystalline solids which are closely packed and symmetric in nature. Based on the crustal abundance, metals are arranged as aluminium, iron, calcium, sodium, titanium, copper, brass, magnesium. New materials were developed from predates by intrinsic modification that is by addition of alloying elements to enhance the mechanical and wear properties of the existing materials.

## **1.3 Ceramic materials**

Any inorganic, non-metallic solid substances that has chemical inertness, high strength, hardness, high melting temperature, low thermal and electrical conductivity as their characteristics but brittle in nature may be termed as ceramics. Alumina, calcia are few examples.

## **1.4 Composite materials**

New materials are developed to meet the customer driven competitive environment by extrinsic modification. Composite materials fall under this category. Composite materials constitute two or more distinct type of materials. Reinforcements are *Experimental Investigation of Mechanical and Wear Behaviour of AZ91 Magnesium Hybrid… DOI: http://dx.doi.org/10.5772/intechopen.104703*

### **Figure 1.**

*Classification of composite materials based on reinforcement and matrix types.*

added to the parent material to improve the properties. **Figure 1** show the classification of composite materials.
