Heterogeneous material joining of sapphire and TC4 alloy with a functionally graded interface

The natural high brittleness of sapphire leads to its poor machinability, which limits its application shape and size. The connection between sapphire and metal provides a new method to prepare large-size sapphire components and complex structural parts. In this study, sapphire and TC4 alloy were joined by spark plasma sintering (SPS) diffusion technology with Al2O3-Ti as interlayer fillers. The effects of filler composition, sintering temperature, microstructure, and phase distribution on the strength of the joint were explored. The results showed that sapphire and TC4 could be well connected by SPS with Al2O3-Ti fillers. The microstructure of the joint showed no obvious defect or element enrichment. The optimized shear strength of sapphire/interlayer(Al2O3-Ti)/TC4 joint reached 121 MPa, and the fracture path mode was sapphire-interlayer-TC4, indicating the strong bonding between the heterogeneous materials. The sapphire/interlayer(Al2O3-Ti)/TC4 structure could relieve the residual stress caused by the difference in the thermal expansion coefficient in direct connection between sapphire and TC4.

Automated summary

The natural brittleness of sapphire limits its machinability, but connecting sapphire with metals provides a new method for preparing large-size components. In this study, sapphire and TC4 alloy were joined using spark plasma sintering with Al2O3-Ti fillers. The optimized joint showed strong bonding between the heterogeneous materials and exhibited a high shear strength of 121 MPa.