**11. Conclusion**

In the present work, a new and cost effective magnesium based alloy hybrid material was developed successfully by stir casting technique. Addition of reinforcements like titanium, titanium dioxide and graphene has shown significant change in material's property. It was inferred from the results obtained that hybrid composites exhibited improved properties than AZ91 base alloy. The main conclusion obtained from comparison of each combination of reinforcements system are listed below


**Figure 20.**

*Optical microscope image of worn surface of AZ91/1%TiO2/0.5%Gr for load 20 N, 40 N, 60 N and 80 N (dry condition).*

Wear resistance of the AZ91 magnesium alloy was greatly enhanced by addition of titanium dioxide and graphene. AZ91–1%TiO2–0.5% Gr showed better wear property in all the test condition of dry and wet under varying load. Under low load conditions AZ91–2%Ti-0.5% Gr also disclosed better wear resistance and moderate difference at high load. AZ91–2%Ti-0.5% Gr showed high hardness but low wear resistance due to the hard Ti particle detachment may lead three body abrasion phenomenon. However, titanium dioxide has sufficient hardness and lubricant property to protective the material from wear. The order of wear resistance B1 > A2 > A1 > B2 > AZ91.

Corrosion resistance was very significant in titanium and graphene combination. Addition of reinforcement greatly prevented the material degradation by formation of stable protective layer. AZ91–2%Ti-0.5% Gr showed high corrosion resistance in

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

**Figure 21.**

*Optical microscope image of worn surface of AZ91/1%Ti/0.5%Gr for load 20 N, 40 N, 60 N, and 80 N (wet condition).*

acidic, neutral and alkaline environment of 3.5% NaCl. The order of corrosion resistance is A2 > A1 > B1 > B2 > AZ91.

Nevertheless all the hybrid composites exhibited better properties than base alloy. Among the four hybrid composites, based on mechanical properties, wear and corrosion behaviour. AZ91–2%Ti-0.5% Gr showed better properties in all aspects.

From engineering application point of view, materials play a key role in design, fabrication, quality, application and cost of the product.

Hence from the present investigation, hybrid composites developed may be considered for the varied field of engineering applications based on the need of usage in different environment like compressive strength or wear resistance or corrosion resistance. Recommended material with improved property based on the property requirement are listed in **Table 20**.

**Figure 22.**

*Optical microscope image of worn surface of AZ91/2%Ti/0.5%Gr for load 20 N, 40 N, 60 N, and 80 N (wet condition).*

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

**Figure 23.**

*Optical microscope image of worn surface of AZ91/1%TiO2/0.5%Gr for load 20 N, 40 N, 60 N, and 80 N (wet condition).*

**Figure 24.**

*Optical microscope image of worn surface of AZ91/2%TiO2/0.5%Gr for load 20 N, 40 N, 60 N, and 80 N (wet condition).*

**Figure 25.** *SEM image of worn surface of AZ91 Mg alloy in (a) dry & (b) wet.*

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

**Figure 26.** *SEM image of worn surface of AZ91/1%Ti/0.5%Gr (a) dry and (b) wet.*

**Figure 27.** *SEM image of worn surface of AZ91/2%Ti/0.5%Gr (a) dry and (b) wet.*

### **Figure 29.**

*SEM image of worn surface of AZ91/2%TiO2/0.5%Gr (a) dry and (b) wet.*


**Table 20.** *Material requirement.* *Experimental Investigation of Mechanical and Wear Behaviour of AZ91 Magnesium Hybrid… DOI: http://dx.doi.org/10.5772/intechopen.104703*
