Microstructure, Tensile Properties, and Wear Resistance of In Situ TiB₂/6061 Composites Prepared by High Energy Ball Milling and Stir Casting

In-situ synthesized TiB₂/6061 composites were prepared from Al-K₂TiF₆-KBF₄ by high energy ball milling and stir casting. Phase analysis and microstructure observation of the samples were characterized by XRD, SEM and EDS, respectively. The effect of TiB₂ particle content on the microstructure, tensile properties and wear resistance of the composites was studied. The results show that the average size of TiB₂ particles is 1 μm, which is polygonal shape. The average grain size of the composites can be refined significantly as the TiB₂ particle mass content increased from 1 to 3%; however, the grain coarsening occurs in the 5 wt.% TiB₂/6061composites. The 3 wt.% TiB₂/6061 composites have best tensile strength, yield strength and Young’s modulus among the composites in ranges of the TiB₂ mass fraction from 1 to 5%. Strengthening mechanisms of the TiB₂/6061 composites were fine grain strengthening, Orwan strengthening and CTE strengthening, in which the CTE strengthening plays an important role as increasing the TiB₂ content. The pin-on-disk wear test results indicated that the average friction coefficient and wear rate of the TiB₂/6061 composites increased firstly and then decreased with increasing the TiB₂ content from 1 to 5 wt.%. The wear mechanism of the TiB₂/6061 composites was discussed.