Nb-modified Ag-Cu-Sn filler metal for brazing CoCrFeNiMoNb high-entropy alloy to oxygen-free copper: microstructural evolution, strengthening mechanisms and joint performance

IF 6.2 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization Pub Date : 2026-10-01 Epub Date: 2026-10-02 DOI:10.1016/j.matchar.2026.117148

Lili Cao, Kuaikuai Wu, Cunjiabei Feng, Siman Zhang, Xindi Wang, Quanbin Lu, Changmao Ji

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引用次数: 0

Abstract

Brazing CoCrFeNiMoNb high-entropy alloys (HEAs) to oxygen-free copper (OFC) remains challenging because conventional Ag-based filler metals often provide insufficient interfacial compatibility and joint reliability. Here, Nb was introduced into Ag₅₀CuSn₁₂ filler metals to regulate interfacial reactions and microstructural evolution in HEA/OFC brazed joints. Nb addition markedly altered elemental redistribution and refined the brazed-seam microstructure, leading to a more homogeneous distribution of reaction products. The joint containing 10 wt% Nb exhibited the best overall performance, achieving a maximum shear strength of 73.65 MPa, approximately 24% higher than that of the Nb-free joint. Its corrosion current density decreased to 1.5060 × 10⁻⁴ A/cm², while the oxidation rate constant reached the minimum value, demonstrating enhanced corrosion and high-temperature oxidation resistance. Excessive Nb addition (12 wt%), however, led to a marked deterioration in corrosion resistance, with the corrosion current density rising to 2.3650 × 10⁻⁴ A/cm², even worse than that of the Nb-free joint. EBSD analysis revealed a refined microstructure with an average grain size of 39.4 μm and no pronounced crystallographic texture. The improved joint performance was primarily attributed to Nb-induced grain refinement, enhanced elemental diffusion, and suppressed growth of brittle CuSn intermetallic compounds; however, excessive Nb precipitates coarse Nb-rich phases that trigger micro-galvanic corrosion and accelerate corrosive medium penetration, thereby degrading joint performance. This work demonstrates an effective Nb-microalloying strategy for developing low-Ag filler metals with balanced mechanical strength and environmental durability for dissimilar brazed joints.

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CoCrFeNiMoNb高熵合金与无氧铜钎焊用铌改性Ag-Cu-Sn钎料：显微组织演变、强化机制及接头性能

将CoCrFeNiMoNb高熵合金（HEAs）钎焊到无氧铜（OFC）上仍然具有挑战性，因为传统的ag基填充金属通常不能提供足够的界面兼容性和连接可靠性。将Nb引入Ag50CuSn12钎料中，调节HEA/OFC钎焊接头的界面反应和微观组织演变。Nb的加入显著改变了元素的再分布，改善了钎缝组织，使反应产物的分布更加均匀。含Nb量为10 wt%的节理整体性能最佳，最大抗剪强度为73.65 MPa，比不含Nb节理提高约24%。腐蚀电流密度降至1.5060 × 10−4 A/cm2，氧化速率常数达到最小值，具有较强的耐蚀性和耐高温氧化性。然而，过量添加Nb （12 wt%）导致接头的耐蚀性明显下降，腐蚀电流密度上升到2.3650 × 10−4 a /cm2，甚至比不添加Nb的接头还要差。EBSD分析显示，合金的显微组织细化，平均晶粒尺寸为39.4 μm，无明显的晶体织构。接头性能的改善主要是由于nb诱导晶粒细化，增强元素扩散，抑制脆性CuSn金属间化合物的生长；然而，过量的Nb析出粗大的富Nb相，引发微电偶腐蚀，加速腐蚀介质渗透，从而降低接头性能。这项工作证明了一种有效的铌微合金化策略，用于开发具有平衡机械强度和环境耐久性的低银填充金属。

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来源期刊

Materials Characterization 工程技术-材料科学：表征与测试

CiteScore

7.60

自引率

8.50%

发文量

746

审稿时长

36 days

期刊介绍： Materials Characterization features original articles and state-of-the-art reviews on theoretical and practical aspects of the structure and behaviour of materials. The Journal focuses on all characterization techniques, including all forms of microscopy (light, electron, acoustic, etc.,) and analysis (especially microanalysis and surface analytical techniques). Developments in both this wide range of techniques and their application to the quantification of the microstructure of materials are essential facets of the Journal. The Journal provides the Materials Scientist/Engineer with up-to-date information on many types of materials with an underlying theme of explaining the behavior of materials using novel approaches. Materials covered by the journal include: Metals & Alloys Ceramics Nanomaterials Biomedical materials Optical materials Composites Natural Materials.