ZrB2 nanoparticles transmuting tribological properties of Al3Zr/AA5052 composite

Good work hardenability, moderate to high strength of AA5052 alloy and high melting point and elastic modulus of Al3Zr with limited wear resistance have been the driving force to transmute Al3Zr/AA5052 composite by generations of ZrB2 nanoparticles. For this purpose, the varying amounts of ZrB2 particles in Al3Zr/AA5052 composite have been produced by direct melt reaction in situ technique. The phase identification, microstructural studies and wear testing have been performed for all the composites. The phase identification and microstructural studies indicate that the ZrB2 particles are formed successfully in the Al3Zr/AA5052Al composite with hexagonal and rectangular morphology within a size range of 10–190 nm. Wear testing results show that friction coefficient (COF) fluctuates with sliding distance, whereas it decreases with normal load. For the composite without ZrB2, the COF is exhibited increasing trend with sliding velocity, while for the hybrid composites initially it decreases, but beyond 2 m/s sliding velocities it starts increasing. Wear studies also show that with ZrB2 generation in Al3Zr/AA5052 composites can be used up to larger loads and higher sliding velocities while being in mild wear regime. It is observed that the mild wear regime extends and COF increases with the increase in vol% of ZrB2 particles. Texture analysis of worn surfaces is in agreement with the results. The present investigation shows that in situ (ZrB2 + Al3Zr)/AA5052 hybrid composites could be a promising material in the applications requiring high wear resistance and high COF such as braking system.