| Summary: | In situ ZA27/TiB<sub>2</sub> composites were synthesized successfully by diluting the in situ Al/TiB<sub>2</sub> composite, which was used as a master alloy. The microstructure and hardness of the developed in situ composites have been investigated. Results have shown that TiB<sub>2</sub> particles distribute uniformly through the matrix and significantly refine the matrix grain. The hardness of the composites was higher than that of the matrix alloy and increased with the increasing TiB<sub>2</sub> content. The dry sliding wear behavior under heavy loads and high rotation speed were studied in detail by using a pin-on-disc wear tester at room temperature. The results revealed that the wear resistance of the composites increased monotonically with the increase in the TiB<sub>2</sub> content. The composites had a lower coefficient of friction, friction temperature, wear rate, and specific wear rate especially under high loads when compared with the matrix alloy. An increase in the applied load increased the wear severity by changing the wear mechanism from abrasion and oxidation to adhesive wear. The composites possess better adhesive wear resistance properties compared with the matrix, which shows obvious adhesive wear as the load increased to 36 N, while the ZA27/3.0% TiB<sub>2</sub> composite did not show adhesive wear until the load increased to 54 N.
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