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The present work has used pin on disc tribometer at atmospheric conditions to examine dry sliding tribological properties of Zn–Al (ZA) alloy and ZA/ZrB2 composites at varying reinforcement of ZrB2 particles (0, 3, 4.5, 6 and 9 vol%), load (10–50 N) and sliding distance (1000–5000 m). The composites were fabricated using stir cast insitu technique and characterized (in terms of morphological and mechanical) by different techniques. Tribological behaviour of composites has been analyzed in terms of wear volume and frictional coefficient. Scanning electron microscopy, surface profilometer and atomic force microscopy tools were employed to analyze the worn surface to show the mechanism of wear to substantiate the obtained results. Obtained results suggest that the insitu formed ZrB2 particles refine the microstructure and improve the mechanical properties of composites. However, at 9 vol% of ZrB2, the matrix grains are refined by 48% and the hardness value is improved by 68% compared to ZA alloy. As the volume percentage (vol%) of ZrB2 rises, wear rate decreases while coefficient of friction (CoF) surge. However, linear rise in wear and CoF with rise in load and sliding distance. At lower load, wear mechanism is oxidative, while at high load, it converts to oxidative-metallic. Composites with 9 vol% ZrB2 show approximately 80% reduction in wear at load (50 N) and sliding distance (5000 m) compared to ZA alloy. These fabricated composites could be utilized for those applications where less wear and high CoF along with high strength are required. [ABSTRACT FROM AUTHOR]

This work presents tribological characteristics of Zinc-Aluminum (Zn-Al) alloy and ZrB2 particles reinforced composites in reciprocating motion under dry conditions. Zn-Al alloy composites with 3, 6, and 9 vol% of ZrB2 particles were fabricated via in-situ stir casting route using resistance-heated muffle furnace. Reciprocating wear tests were conducted on all compositions using Multifunctional Tribometer in a range of 10 N–55 N load and sliding speed of 0.075 m/s–0.300 m/s. Results were analyzed for coefficient of friction and wear. Tools such as scanning electron microscope for texture and profilometer for surface roughness were used to analyze relaxed layer of all compositions to understand tribological phenomena. Significant improvement was seen with increased amount of hard ZrB2 particles in tribological properties. [ABSTRACT FROM AUTHOR]

The focus of this study is the investigation of the microstructural and mechanical properties of in-situ (0-9wt%) ZrB2/Al7068 nanocomposites synthesized by ultrasonic-assisted stir casting technique. The optimized reaction time of 30 minutes resulted in ZrB2 with a mean size of 46 nm. The combined mixing by mechanical stirring for 25 minutes and ultrasonic vibration for 5 minutes indicated an even distribution at the lower ZrB2 fraction (≤ 2wt%), whereas interdendritic became prominent with a higher ZrB2 fraction. The addition of ZrB2 increased the tensile strength upto 2wt% nanocomposite (328 MPa), followed by gradual decrement with further addition of ZrB2. Interestingly, a continuous increment in total elongation is observed with increasing ZrB2 in the matrix. Grain refinement is observed in all the nanocomposites compared to the base alloy, but the least grain size (87 μm) obtained for the 2wt% ZrB2 nanocomposite. The lower weight fraction of ZrB2 (1wt% and 2wt%) indicated a uniform distribution of reinforcement particles in the matrix, and higher ZrB2 addition indicated particle agglomeration. [ABSTRACT FROM AUTHOR]