Effect Of Y₂O₃on The Mechanical Properties And Microstructures Of Ti/Al₂O₃Composites

It is easy to find that the manufacture of Ti/Al2O3composites can be applied to the aerospace, new tools and advanced manufacturing technology due to the fact that Ti and Al2O3have the advantages of similar thermal expansion coefficient, excellent physical and chemical compatibility, qualitative light, corrosion resistance, etc.Material properties can be improved by hot pressing sintering on account of controlling the interface reaction through adding the appropriate rare earth oxides. The orthogonal experiment and the optimized results of Ti/Al2O3composites were:sintering temperature1450℃, sintering pressure30MPa, holding time60min, Y2O3addition0.5vol%. According to the orthogonal experiment, the bending strength, fracture toughness, micro hardness, relative density were respectively588.08MPa、16.15MPa-m1/2、13.34GPa、97.46%。The thermodynamic state function of Ti/Al2O3composites was studied. The Al2O3dissolution and therefore the diffusion of oxygen and aluminum into titanium is requirement for the formation of Ti-Al intermetallics. By the thermodynamic calculation (△GTi3Al<△GTiAl<0), it is easy to find that the Ti3Al phase is produced easily. By introducing Y2O3to Ti/Al2O3composites, Y-Al compounds can be formed (△GYAl2<△GYAl<△GTiAl<△GTiAl<0) because yttrium oxide decompose, then the reaction happen between Y and Al,The sintering process can be divided into three stages including the rearrangement of particles and surface diffusion, the mass transfer state with volume diffusion and lattice diffusion and the densification state with plastic flow under pressing. By doping Y2O3, it is to indicate that the composition of phase have changed and the brittle Ti3Al phase was inhibited so that the performance of composites was improved.Studying of Y2O3on the strengthening and toughening of Ti/Al2O3composites showing that the fracture mode transforms from the intergranular fracture to the mixture of the intergranular fracture and transgranular fracture with crack bridging and crack deflection in order to improve the toughness of composites.