Effect of TiC on Microstructure and Strength of Al-Bi-Cu Alloys

TiC particles synthesized in situ by reacting K2TiF6 and graphite in molten aluminum were introduced into Al-Bi-Cu alloys to control its microstructure, increase its tensile strength and improve its wear performance. Al-Bi-Cu alloy has serious coarsening and macrosegregation behaviors during solidification due to the liquid phase separation. However, the coarsening and macrosegregation of Bi-rich phase were significantly impeded by adding 0.5 wt.%-2 wt.% TiC due to the heterogeneous nucleation and self-assembly behaviors provided by TiC particles. The average grain size of α-Al decreased from 36.6 μm (0.5 wt.% TiC) to 18.9 µm (2 wt.% TiC), and the average size of the Bi-rich phase decreased from 4.56 µm (0.5 wt.% TiC) to 3.26 µm (2 wt.% TiC). The results showed that the addition of TiC refines the size of grains and Bi-rich phases and solves the problem of coarsening and macrosegregation caused by liquid phase separation in the alloy. The tensile strength and elongation of the Al-Bi-Cu alloy are improved simultaneously after adding TiC particles and reach their maximum values at a TiC content of 1wt.%, which are 236MPa and 12.46%, respectively. In addition, the alloy containing 1 wt.% TiC has the lowest coefficient of friction and wear loss with the worn surface smooth and flat, indicating that the uniformly dispersed Bi-rich phase is beneficial to improve the friction and wear performance of the alloy.