Abstract
This research work aims at finding the optimum process parameters for the laser welding of AA7020 aluminium alloys. The use of 7xxx series alloys is limited because of weldability problems, such as hot cracking, porosity, and softening of the fusion zone despite its higher specific strength-to-weight ratio. AA7020 aluminium alloy was welded while varying the process parameters so as to obtain optimal welding efficiency. The welded samples were analysed to reveal the microstructure, defects, and mechanical properties of the welded zone. The samples were prepared from a plate of AA7020, which was hot rolled at a temperature of 470 °С to a thickness of 1 mm. The welding was carried out at an overlap of 0.25 mm, duration of 14 ms and argon shield gas flow rate of 15 L/min. Process parameters, such as peak power, welding speed, and pulse shaping, were varied. The samples were welded with Al-5Ti-B and Al-5Mg as filler metals. The welding speed, peak power, and pulse shaping have a great influence on the weldability and hot cracking susceptibility of the aluminium alloy. Al-5Ti-B improves the microstructure and ultimate tensile strength of AA7020 aluminium alloy.
Highlights
As environmental awareness grows among consumers as well as government agencies, attempts to improve fuel economy in automobiles are accelerating [1,2]
The ability of a steel body structure to deliver weight savings is limited, so the use of aluminium in auto body structures is increasing, and is projected to expand further in the decade [3]. Owing to their low density and good mechanical properties, aluminium alloys are increasingly being employed in many important manufacturing areas, such as the automobile industries, aeronautics and the military [4,5,6]
laser beam welding (LBW) has accounted for a 5% reduction in the weight of Airbus A300 series structures and has been employed to join some parts of the fuselage [4]
Summary
As environmental awareness grows among consumers as well as government agencies, attempts to improve fuel economy in automobiles are accelerating [1,2]. The ability of a steel body structure to deliver weight savings is limited, so the use of aluminium in auto body structures is increasing, and is projected to expand further in the decade [3] Owing to their low density and good mechanical properties, aluminium alloys are increasingly being employed in many important manufacturing areas, such as the automobile industries, aeronautics and the military [4,5,6]. AA7020 (Al-Zn-Mg) has moderate strength and is widely used in welded joints of armoured vehicles, cryogenic pressure vessels, components of spacecraft liquid-propellant engines, and bridge beams for roads and railroad systems [17] Process parameters such as laser power, welding speed, defocusing distance, feed rate and pulse shaping have a strong influence on the mechanical properties, weld penetration and bead quality; high speed may result in incomplete fusion, porosity, or high spattering, and high laser power can lead to collapse and instability of the weld pool. Laser power, welding speed, and pulse shaping were varied as well as the filler metal used to evaluate their effect on the microstructure and mechanical properties of the welded sample
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