Microstructural evolution and strengthening mechanism of U71Mn steel joints fabricated by friction-flash hybrid welding

IF 7.6 2区材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY Materials & Design Pub Date : 2024-11-01 DOI:10.1016/j.matdes.2024.113403

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Abstract

The softening layer formed by the ferrite in the welding interface can significantly reduce the mechanical properties of traditional flash butt welding joints. This study proposed a flash-friction hybrid welding method to address the issue of the ferrite softening layer and comprehensively investigated the impact of vibration friction speed on joint performance. The results showed that increasing the vibration friction speed could effectively inhibit the formation of the ferrite softening layer in the weld center zone (WCZ) and enhance the mechanical properties of the joint. When the vibration friction speed was 3 mm/s, the tensile strength of the joint reached its maximum value of 982.9 MPa, approximately equal to 97.3 % of that of the base material (BM). The fracture occurred in the heat-affected zone (HAZ) and was characterized by a ductile fracture mechanism. Moreover, the microstructural analysis revealed that dynamic recrystallization (DRX) occurred in the WCZ, thermo-mechanically affected zone (TMAZ), and fine-grained zone (FGZ)-HAZ of the joint. Compared to the BM, the grain size significantly decreased, and the thickness and spacing of lamellar cementite also reduced. These microstructural evolutions also contributed to the enhanced mechanical properties of the joints. This study provided new insights for welding in the rail transportation field.

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摩擦闪光混合焊接 U71Mn 钢接头的微结构演变和强化机理

铁素体在焊接界面形成的软化层会显著降低传统闪光对焊接头的机械性能。本研究针对铁素体软化层问题提出了一种闪光摩擦混合焊接方法，并全面研究了振动摩擦速度对接头性能的影响。结果表明，提高振动摩擦速度可有效抑制焊接中心区（WCZ）铁素体软化层的形成，提高接头的力学性能。当振动摩擦速度为 3 mm/s 时，接头的抗拉强度达到最大值 982.9 MPa，约等于母材（BM）抗拉强度的 97.3%。断裂发生在热影响区（HAZ），断裂机理为韧性断裂。此外，微观结构分析表明，动态再结晶（DRX）发生在接头的WCZ、热机械影响区（TMAZ）和细晶粒区（FGZ）-HAZ。与 BM 相比，晶粒尺寸明显减小，片状水泥土的厚度和间距也有所减少。这些微结构演变也有助于提高接头的机械性能。这项研究为轨道交通领域的焊接提供了新的见解。

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来源期刊

Materials & Design Engineering-Mechanical Engineering

CiteScore

14.30

自引率

7.10%

发文量

1028

审稿时长

85 days

期刊介绍： Materials and Design is a multi-disciplinary journal that publishes original research reports, review articles, and express communications. The journal focuses on studying the structure and properties of inorganic and organic materials, advancements in synthesis, processing, characterization, and testing, the design of materials and engineering systems, and their applications in technology. It aims to bring together various aspects of materials science, engineering, physics, and chemistry. The journal explores themes ranging from materials to design and aims to reveal the connections between natural and artificial materials, as well as experiment and modeling. Manuscripts submitted to Materials and Design should contain elements of discovery and surprise, as they often contribute new insights into the architecture and function of matter.