Microstructure evolution and mechanical properties of brazing seam of SiCp/Al composites-TC4 titanium alloy composite structure with different La content

This paper presented the design of a new type of active filler metal Al-17.0Cu-8.0 Mg-xLa (x = 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 wt%) for vacuum brazing of composites 55 % SiC_p/ZL102 and TC4. The effects of La on the microstructure and properties of brazing alloy and on the joint were studied. The results demonstrated as follows. The La element has a refining effect on the matrix structure of the brazing master alloy, which made the intergranular network of the structure clearer. High level of the element La resulted in the production of more oxides in the brazing alloy. The increase of La content led to the brazing alloy melting temperature decreased and the brazing seam thickness increased. A layer of tetragonal intermetallic compound τ₁(Ti₇Al₅Si₁₂) phase with (Mohanavel et al., 2021; Wang et al., 2021; Zhu et al., 2018; Bhong et al., 2023; Egbo, 2021; Salonitis et al., 2010; Chen et al., 2023; Chen et al., 2024; Niu et al., 2019; Tariq et al., 2014; Du et al., 2016; Ma et al., 2015; Tang et al., 2021; Chong et al., 2021; Hekner et al., 2017; Yuan et al., 2023; Misra, 1991; Yan et al., 2022; Qiu et al., 2023; Dong et al., 2023; Li et al., 2023; Ma et al., 2020; Chen et al., 2024; Hong et al., 2023; Chen et al., 2024; Zhang et al., 2023; Zuo et al., 2020; Zhang et al., 2023; Zhao et al., 2022; Li et al., 2023; Xie et al., 2022) [1-31] crystal band axis was formed on the TC4 side. The intermetallic compound at the brazing seam gradually extended to the composite side with the increase of La content. Needle-like structure was transformed into massive structure with increased La content, and the width of the brazing seam increased. The shear strength reached the highest value of 88.0 MPa at 2.0 % La. The joint broke at the brazing seam, and the fracture behavior belongs to brittle fracture.