Influence of ZrB2 hard ceramic reinforcement on mechanical and wear properties of aluminum

In this work, the effect of ZrB2 (0, 5, 10 and 20 vol%) ceramic reinforcement on densification, structure, and properties of mechanically alloyed Al was investigated. The milling of Al-ZrB2 powder compositions resulted in formation of agglomerates with varied size. In particular, the size of agglomerates was reduced considerably with increased addition of ZrB2 to Al. Interestingly, the densification of hot pressed Al increased from 96.06% to 99.22% with ZrB2 addition. The reduction of agglomerates size was attributed to the enhanced densification of Al-ZrB2 composites. Pure Al showed relatively low hardness (0.94 GPa) and it was improved to 1.78 GPa with the addition of 20 vol% ZrB2. The mechanical properties have significantly been improved for Al-ZrB2 composites. Especially Al - 20 vol% ZrB2 possessed a very high yield strength (529 MPa), compressive strength (630 MPa) and compressive strain of 19.25%. Realization of such a good combination of mechanical properties is the highest ever reported for Al composites so far in the literature. The coefficient of friction (COF) of Al-ZrB2 varied narrowly between 0.33 and 0.40 after dry sliding wear against steel disc. The wear rate of Al-ZrB2 composites was within mild wear regime and varied between 98.88 x 10(-6) and 34.66 x 10(-6) mm(3)/Nm. Among all the compositions, Al- 20 vol% ZrB2 composite exhibited the lowest wear rate and high wear rate was noted for pure Al. Mild abrasion, tribo-oxidation, third body wear (wear debris) and delamination were the major material removal mechanisms for Al-ZrB2 composites. Overall the hardness, strength and wear resistance of Al- 20 vol% ZrB2 composite was improved by 84.3%, 84.3% and 64.2%, respectively when compared to pure Al.