Direct joining of sapphire and Invar alloy by nanosecond laser

Le résumé fourni par la source

• The direct joining of single-crystal sapphire and Invar alloy using a nanosecond laser is demonstrated for the first time in this study. • The interface of sapphire/Invar alloy joint is well-formed and without the occurrence of micro-cracks or porosity defects. Under the impact of the nanosecond laser, the Invar alloy is splashed into the molten sapphire and thus mixed phases. • The joint domain is composed of mixed phases of Al 2 O 3 and Fe-36Ni. • The primary bonding mechanism of the joint is attributed to mechanical mixing and interlocking. • The mechanical interlocking effect generated by the conical weld structure formed in the laser irradiation zone plays a critical role in enhancing the shear strength of the joints. The direct joining of single-crystal sapphire and Invar alloy using a nanosecond laser is demonstrated for the first time in this study. The macro- and microstructures of the sapphire/Invar alloy joints were analyzed, along with an investigation of their compositional characteristics. Based on this, the effects of nanosecond laser processing parameters on the joint’s macro- and microstructures and its mechanical performance were explored. The typical fracture morphologies of the sapphire/Invar alloy joints were examined, revealing the fracture mechanisms involved. The laser-irradiated area exhibited a conical molten zone, predominantly composed of sapphire with a small amount of Invar alloy particles. No new phases were detected in the joint region, and the primary joining mechanism was identified as mechanical interlocking and embedding. After optimizing the nanosecond laser welding parameters, the joint’s shear strength reached 123.2 MPa. Additionally, the sealed sapphire/Invar alloy samples welded by nanosecond laser passed a 336-hour water resistance test without any leakage. The mechanical interlocking effect generated by the conical weld seam structure in the laser-irradiated area played a key role in enhancing shear strength.

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