Ameliorating the ductility of silicon-modified titanium alloys with graphene nanoplatelets

The incorporation of silicon has been recognized for its capacity to improve the high-temperature performance of titanium alloys, albeit at the expense of their plasticity. In this study, silicon-modified Ti-6Al-4V alloy reinforced with in-situ exfoliated graphene nanoplatelets (GNPs) (SG-Ti64) was prepared via three-dimensional vibration milling and spark plasma sintering. A moderate quantity of silicon particles facilitated the homogeneous dispersion of in-situ exfoliated GNPs, and the uniformly dispersed GNPs with high quality played a pivotal role in transitioning the microstructure of Ti64 from a Widmanstatten to an equiaxed with significantly refined grains. Such microstructural evolution effectively mitigated the silicide-induced stress concentration within grains, thereby significantly ameliorating the ductility of SG-Ti64. Due to the solid solution strengthening of silicon, the load transfer of GNPs, and the equiaxed microstructure with refined grains, the SG-Ti64 with 0.70 wt% GNPs and 0.30 wt% silicon (0.3SG-Ti64) exhibits the best combination of strength and ductility. Compared to Ti64 monolithically modified with 0.30 wt% silicon, the ductility of 0.3SG-Ti64 is more than double while the strength is improved by 12.8 %. This study heralds a new strategy for developing high-temperature titanium alloys with well-balanced strength-ductility.