表面纳米处理对高熵合金与不锈钢扩散焊接头组织及力学性能的影响

李琪; 高海涛; 刘凤美; 李丽坤; 高世一

doi:10.16490/j.cnki.issn.1001-3660.2025.19.016

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表面技术 ›› 2025, Vol. 54 ›› Issue (19) : 186-197. DOI: 10.16490/j.cnki.issn.1001-3660.2025.19.016

表面强化技术

表面纳米处理对高熵合金与不锈钢扩散焊接头组织及力学性能的影响

李琪, 高海涛^*, 刘凤美, 李丽坤, 高世一

作者信息 +

Effects of Surface Nanotreatment on Microstructure and Mechanical Properties of High-entropy Alloys and Stainless Steel Diffusion Welded Joints

LI Qi, GAO Haitao^*, LIU Fengmei, LI Likun, GAO Shiyi

Author information +

文章历史 +

摘要

目的采用机械研磨方法,在CoCrFeMnNi高熵合金表层制备纳米晶粒,以此来应对CoCrFeMnNi高熵合金的扩散迟滞效应。通过在高熵合金表面制备纳米化晶层,利用纳米晶粒的高扩散系数促进界面的有效连接,实现高熵合金与不锈钢的高可靠性连接。方法采用SEM、XRD、EBSD研究纳米化高熵合金的表面微观形貌、成分组成、厚度及晶粒度大小分布,并采用维氏硬度机、SEM、TEM、万能试验机对表面纳米化前后CoCrFeMnNi高熵合金和304不锈钢扩散连接区域的硬度分布、元素分布、微观结构、相组成、接头的力学性能及断口形貌进行分析研究。结果经表面机械研磨处理后,高熵合金的表面晶粒尺寸从10~40 μm减小到11~19 nm。通过表面纳米化处理能够有效增大Fe原子在扩散焊中的扩散距离,在焊接温度为900 ℃、保温时间为2 h、压力为20 MPa的扩散连接工艺下,经过4 h表面机械研磨处理后,Fe原子扩散距离从5.6 μm增至19.4 μm。显微硬度结果表明,表面机械研磨处理CoCrFeMnNi/304SS接头界面处不存在因Kirkendall效应而产生的有害硬相和孔隙。经过表面机械研磨,在900 ℃的焊接温度下经4 h机械研磨处理后,扩散焊接头的抗剪强度达到357 MPa,与未机械研磨处理接头（257 MPa）相比,提高了38.9%。结论通过表面纳米化处理机制可以有效克服高熵合金的扩散迟滞效应,通过纳米化处理可以有效提高高熵合金的扩散速率,从而有效提高了高熵合金和不锈钢接头的力学性能。

Abstract

Nanocrystalline grains are prepared on the surface layer of CoCrFeMnNi high-entropy alloy by mechanical polishing to address the diffusion hysteresis effect of CoCrFeMnNi high-entropy alloy. By creating a nanostructured layer on the surface, a "short-circuit diffusion" strategy is employed, which increases grain boundaries and utilizes the high diffusion coefficient of nanocrystalline grains to enhance effective bonding at the interface. This approach achieves a highly reliable connection between the high-entropy alloy and stainless steel. The surface micro-morphology, composition, thickness, and grain size distribution of the nanostructured high-entropy alloy are analyzed using SEM, XRD, and EBSD techniques. The hardness distribution, elemental distribution in the joint area, microstructure and phase composition of the joint, mechanical properties, and fracture morphology of the CoCrFeMnNi high-entropy alloy and 304 stainless steel diffusion bonding area are examined before and after surface nanostructuring, with a Vickers hardness tester, SEM, TEM, and a universal tensile testing machine. A nanocrystalline layer is formed on the surface of the CoCrFeMnNi high-entropy alloy through surface mechanical polishing. The surface grain size of the high-entropy alloy is reduced from 10-40 μm to approximately 11-19 nm. After 2 hours of mechanical polishing, a nanocrystalline region with a thickness of about 66 μm is created, and after 4 hours, this thickness increases to approximately 154 μm. Although the diffraction peak positions of the CoCrFeMnNi high-entropy alloy does not change post-polishing, the peaks broadened, indicating that the crystal structure remains unchanged, maintaining a single face-centered cubic structure. Surface nanochemical processing effectively increases the diffusion distance of Fe atoms. Under the diffusion connection process with welding temperature of 900 ℃, insulation time of 2 h and pressure of 20 MPa, the diffusion distance of Fe atoms increases from 5.6 μm to 11.2 μm after 2 hours, and to 19.4 μm after 4 hours of surface mechanical polishing, demonstrating that this technique successfully overcomes the diffusion sluggishness effect of the high-entropy alloy. Microhardness results indicate that no detrimental hard phases or voids caused by the Kirkendall effect are present at the interface of the CoCrFeMnNi/304SS joint following surface mechanical polishing. Under the diffusion connection process with welding temperature of 900 ℃, insulation time of 2 h and pressure of 20 MPa, the shear strength of the diffusion welded joint after 2 hours of mechanical polishing reaches 304 MPa, and after 4 hours, it increases to 357 MPa, reflecting an enhancement of 18.9% and 38.9%, respectively, compared with the unpolished joint (257 MPa). This signifies a substantial improvement in joint strength. The fracture morphology of the joint without surface mechanical polishing at 900 ℃ displays a mixture of a few dimples and cleavage facets, with the fracture primarily exhibiting brittle characteristics. After 2 hours of surface mechanical polishing, some tearing-type fracture features are observed, although a full transition to ductile fracture does not occur. In contrast, the fracture morphology after 4 hours of polishing exhibits typical ductile fracture characteristics. In conclusion, this study demonstrates that the surface nanostructuring treatment mechanism can effectively mitigate the diffusion sluggishness effect in high-entropy alloys, and that nanostructuring significantly enhances the diffusion rate of these alloys, thereby improving the mechanical properties of joints between high-entropy alloys and stainless steel.

导出引用

李琪, 高海涛, 刘凤美, 李丽坤, 高世一. 表面纳米处理对高熵合金与不锈钢扩散焊接头组织及力学性能的影响[J]. 表面技术. 2025, 54(19): 186-197 https://doi.org/10.16490/j.cnki.issn.1001-3660.2025.19.016

LI Qi, GAO Haitao, LIU Fengmei, LI Likun, GAO Shiyi. Effects of Surface Nanotreatment on Microstructure and Mechanical Properties of High-entropy Alloys and Stainless Steel Diffusion Welded Joints[J]. Surface Technology. 2025, 54(19): 186-197 https://doi.org/10.16490/j.cnki.issn.1001-3660.2025.19.016

中图分类号： TG456

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