Influence of ZrB < inf > 2 < /inf > hard ceramic reinforcement on mechanical and wear properties of aluminum

Abstract

In this work, the effect of ZrB 2 (0, 5, 10 and 20 vol%) ceramic reinforcement on densification, structure, and properties of mechanically alloyed Al was investigated. The milling of Al-ZrB 2 powder compositions resulted in formation of agglomerates with varied size. In particular, the size of agglomerates was reduced considerably with increased addition of ZrB 2 to Al. Interestingly, the densification of hot pressed Al increased from 96.06% to 99.22% with ZrB 2 addition. The reduction of agglomerates size was attributed to the enhanced densification of Al-ZrB 2 composites. Pure Al showed relatively low hardness (0.94 GPa) and it was improved to 1.78 GPa with the addition of 20 vol% ZrB 2 . The mechanical properties have significantly been improved for Al-ZrB 2 composites. Especially Al - 20 vol% ZrB 2 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-ZrB 2 varied narrowly between 0.33 and 0.40 after dry sliding wear against steel disc. The wear rate of Al-ZrB 2 composites was within mild wear regime and varied between 98.88 × 10 −6 and 34.66 × 10 −6 mm 3 /Nm. Among all the compositions, Al - 20 vol% ZrB 2 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-ZrB 2 composites. Overall the hardness, strength and wear resistance of Al - 20 vol% ZrB 2 composite was improved by 84.3%, 84.3% and 64.2%, respectively when compared to pure Al.