**7.2 Density measurement**

The results of density test are illustrated in the **Table 4**. The results showed that denser hybrid composites produced among them was AZ91 + 2%Ti +0.5% Gr. The theoretical density was found to be higher than actual density of the hybrid composites.

It was noted from the result that the densities of each hybrid composites were higher than the base matrix clearly signifying that porosity will be reduced by increase *Experimental Investigation of Mechanical and Wear Behaviour of AZ91 Magnesium Hybrid… DOI: http://dx.doi.org/10.5772/intechopen.104703*

### **Figure 6.**

*AZ91/1% TiO2/0.5% Gr (a) optical micrograph (b) SEM image (c).*

the weight percentage of the reinforcement as shown in **Figures 8** and **9**. The increase in density attributes to increase in hardness and decrease in porosity.

## **7.3 Tensile test**

The tensile tests are carried out at room temperature and results of all the hybrid composites are depicted in **Table 5** and **Figure 9**. It revealed that the addition of reinforcement titanium and graphene have gradually increased the strength of the material than the monolithic AZ91. The addition of titanium shows improved ductility than the base matrix. The diffused magnesium and aluminium with titanium yielded higher tensile strength due to the addition of reinforcement graphene, inspite of its high thermal conductivity yet has no chemical reaction with the matrix [25].

The titanium dioxide and graphene hybrid composites exhibited higher strength but probably low ductility. It was noticed that the decrease in ductility may be due to the increase in weight percentage of the reinforcement creating a strained lattice and also void nucleation. The strength of hybrid composites depended on the bonding between the AZ91 magnesium matrix and reinforcements. In both the cases, the graphene acts diffusion barrier for aluminium and magnesium forming intermetallic bond which have poor stability.

### **Figure 7.**

*AZ91/2% TiO2/0.5% Gr (a) optical micrograph (b) SEM image (c) EDS spectrum.*


### **Table 4.**

*Density of hybrid composite material.*
