Effect of zinc on the fracture behavior of galvanized steel/6061 aluminum alloy by laser brazing
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RESEARCH PAPER
Effect of zinc on the fracture behavior of galvanized steel/6061 aluminum alloy by laser brazing Peilei Zhang 1,2
&
Haichuan Shi 1,2 & Yingtao Tian 3 & Zhishui Yu 1,2 & Di Wu 1,2
Received: 18 November 2019 / Accepted: 9 September 2020 # International Institute of Welding 2020
Abstract The galvanized steel with thickness of 2 mm was joined to 6061 with thickness of 2 mm by laser fusion-brazing process. The filler wire was AlSi5 and wire feed speeds were 2.8, 3.0, and 3.2 m/min, respectively. Microstructure and mechanical properties of the joints were investigated. The Zn-rich zone formed in the area of the seam toe was analyzed by means of optical microscope, scanning electron microscope, and energy-dispersive spectroscopy. Meanwhile, the Fe2Al5Zn0.4phasećFe(Al,Si)0.5 phase, and Fe(Al,Si)0.7 phase were found at the galvanized steel/brazed metal interface along the weld seam. According to tensile test, the strength of the joints was 31.6 MPa (wire feed speed is 2.8 m/min), 61.4 MPa (3.0 m/min), and 70.4 MPa (3.5 m/min), the failure occurred in interfacial layer at the bottom of the joint. Keywords Laser brazing . Galvanized steel . Aluminum alloy . Evaporation . Fracture behavior
1 Introduction In auto industries, shipbuilding and aircraft construction, lightweight aluminum alloy and steel hybrid structure can significantly reduce fuel consumption and decrease air pollution [1]. Aluminum alloy has many virtues, such as its low density, good corrosion resistance, excellent workability, and machinability [2]. Therefore, steel-steel components have been replaced by aluminum-steel hybrid structures. A great amount of researches on joining aluminum to steel have been carried on to satisfy the necessities of many industrial applications. However, the differences of thermal conductivity, Recommended for publication by Commission II - Arc Welding and Filler Metals * Peilei Zhang [email protected] * Yingtao Tian [email protected] 1
School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
2
Shanghai Collaborative Innovation Center of Laser of Manufacturing Technology, Shanghai 201620, China
3
Department of Engineering, Lancaster University, Bailrigg, Lancaster LA1 4YW, UK
coefficient of linear expansion, between aluminum and steel bring difficulties by fusion welding. Because the density of aluminum is smaller than steel, thus, liquid aluminum can float on the surface of steel in fusion welding process which has difficulty in forming reliable joints [3]. In the fusion welding process, the main problems are the generation of pores, cracks, and thermal stresses which severely affect the properties of the welded joints. In the welding process under the improper protection, aluminum is easy to be oxidized which lead to generate Al2O3 with high melting point which lead to slag in weld, incomplete fusion, and other defects [4]. Many approaches have been made to join aluminum to steel in recent years [5]. Such as friction welding, explosion welding [6], res
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