**7.5 Hardness**

**Table 7** shows the test result of micro hardness of hybrid composites and monolithic AZ91 magnesium alloy.


### **Table 5.**

*Tensile strength of AZ91 magnesium hybrid composite material.*


### **Table 6.**

*Compressive strength of hybrid composites.*

**Figure 10.** *Ultimate compressive strength.*

The results revealed that increase in micro hardness of the reference alloy AZ91 magnesium had increased due to the addition of reinforcements of titanium/graphene and titanium dioxide/graphene. Among the two reinforcement's combinations, it was evident that the hybrid composites titanium/graphene combination exhibited better hardness than the other combination of reinforcement.

The increase in hardness of hybrid composites was due to presence of harder titanium and graphene particles in the reference which assist in load bearing capacity


*Experimental Investigation of Mechanical and Wear Behaviour of AZ91 Magnesium Hybrid… DOI: http://dx.doi.org/10.5772/intechopen.104703*

**Table 7.** *Hardness.*

### **Figure 11.** *Hardness.*

of matrix [26]. Addition of graphene to AZ91 significantly improved the hardness of the materials. Within the hybrid composites samples, increase in hardness was very significant as the attribute to uniform distribution of reinforcements. The AZ91/2% Ti/0.5% Gr hybrid composite showed the highest hardness and compressive strength among the entire hybrid composite. **Figure 11** shows the micro hardness of all the hybrid composite samples and AZ91 reference alloy.
