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 mu m, 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.