Microstructure and Oxidation Resistance of Graphene/Ti-Al-Sn-Zr-Nb-Mo-Si Composites Prepared by Spark Plasma Sintering

Abstract

Ti-6Al-4Sn-9Zr-1.21Nb-1.6Mo-0.3Si powders and graphene nanoplatelets (GNPs) were used as the raw materials to prepare GNPs/Ti-Al-Sn-Zr-Nb-Mo-Si composites by using spark plasma sintering method. The effect of adding 1-4 wt.% GNPs on the porosity, hardness, microstructure, phase composition and oxidation resistance of composites at 1073 and 1173 K were investigated. The results show that all GNPs/Ti-Al-Sn-Zr-Nb-Mo-Si composites before oxidation possessed the porosity of not more than 0.20% and the average hardness of higher than 480 HV. The porosity of composites decreased and the average hardness of composites increased, while the content of graphene increased. Compared with the matrix, Ti-6Al-4Sn-9Zr-1.21Nb-1.6Mo-0.3Si-4GNP possessed highest hardness (533.9 HV) and lowest porosity (0.14%). Compared with the composites before oxidation, the hardness of the composites oxidized at 1073 K and 1173K decreased by less than 10%, which meant that the composites still possessed excellent performance at high temperature. GNPs/Ti-Al-Sn-Zr-Nb-Mo-Si composites with adding various graphene oxidized at 1073 K and 1173K were composed of TiO2, Al2O3, SiO2, SnO2, Nb2O5, Ti3O5, ZrO2 and MoO3 and MoSi2 was just generated after oxidation at 1073 K. The GNPs content and oxidation temperature influenced the oxidation resistance. At 1173 K, the composite with 1 wt.% GNPs possessed the lowest average oxidation rate (2.57 × 10−3 g m−2 h−1), which was about 84.7% less than that of the matrix alloy, and its thickness of the oxidized layer was thinnest, which was about 12 μm. The oxidation resistance of the composites with adding 1-4 wt.% GNPs was better than the unreinforced alloy.