Effect of Activating Flux on Microstructure and Mechanical Properties of SiCp/6061Al Composite Joints in Laser Welding

SUN Yuxuan; LI Pubo; ZHOU Hai; ZHANG Yongqiang; WU Bintao

doi:10.3969/j.issn.1674-6457.2026.03.019

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Journal of Netshape Forming Engineering ›› 2026, Vol. 18 ›› Issue (3) : 173-183. DOI: 10.3969/j.issn.1674-6457.2026.03.019

Composites Forming

Effect of Activating Flux on Microstructure and Mechanical Properties of SiCp/6061Al Composite Joints in Laser Welding

SUN Yuxuan¹, LI Pubo^1,*, ZHOU Hai², ZHANG Yongqiang³, WU Bintao¹

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Abstract

The work aims to investigate the effects of multi-component activating fluxes (Cr₂O₃, Na₃AlF₆, Si) on the weld morphology and mechanical properties of joints in laser welding of SiCp/6061Al composites to address the issues of porosity, cracking, and brittle Al₄C₃ phase formation commonly encountered during laser welding. Different flux formulations were designed and applied to the top surface of the butt joints. Laser welding experiments were conducted under consistent process parameters, followed by characterization of the weld microstructure and mechanical properties. The results indicated that, compared with the single-component Cr₂O₃ flux, the dual-component fluxes preliminarily demonstrated a synergistic effect among the constituents, significantly influencing the weld macrostructure, microstructure, and joint mechanical properties. The Cr₂O₃-Na₃AlF₆-Si three-component activating flux produced the optimal synergistic effect: It significantly reduced weld porosity; inhibited the formation and growth of the detrimental Al₄C₃ phase, controlling its average size (5-20 μm); and enhanced the joint tensile strength (from 110.6 MPa to 160.5 MPa). Simultaneously, the combined action of the activating fluxes optimized the welding thermal process and molten pool dynamics, promoting the formation of a continuous gradient microstructure from the equiaxed grain zone to the Al₄C₃-enriched zone, and suppressed the continuous network precipitation of the hard and brittle Mg₂Si phase at grain boundaries. This research demonstrates that the pre-placed multi-component activating flux coating process is an effective method for improving the laser welding quality of SiCp/Al composites.

Key words

SiCp/6061Al composites / laser welding / active agent / synergistic effect / mechanical properties

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SUN Yuxuan, LI Pubo, ZHOU Hai, ZHANG Yongqiang, WU Bintao. Effect of Activating Flux on Microstructure and Mechanical Properties of SiCp/6061Al Composite Joints in Laser Welding[J]. Journal of Netshape Forming Engineering. 2026, 18(3): 173-183 https://doi.org/10.3969/j.issn.1674-6457.2026.03.019

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Funding

Natural Science Foundation of Ningxia (2024AAC02007); Key R&D Project of Ningxia (2024BEE03004); National Natural Science Foundation of China (52361030)