Abstract
The effect of pulse laser welding parameters and filler metal on microstructure and mechanical properties of the new heat-treatable, wieldable, cryogenic Al-4.7Mg-0.32Mn-0.21Sc-0.1Zr alloy were investigated. The optimum parameters of pulsed laser welding were found. They were 330–340 V in voltage, 0.2–0.25 mm in pulse overlap with 12 ms duration, and 2 mm/s speed and ramp-down pulse shape. Pulsed laser welding without and with Al-5Mg filler metal led to the formation of duplex (columnar and fine grains) as-cast structures with hot cracks and gas porosity as defects in the weld zone. Using Al-5Ti-1B filler metal for welding led to the formation of the fine grain structure with an average grain size of 4 ± 0.2 µm and without any weld defects. The average concentration of Mg is 2.8%; Mn, 0.2%; Zr, 0.1%; Sc, 0.15%; and Ti, 2.1% were formed in the weld. The ultimate tensile strength (UTS) of the welded alloy with AlTiB was 260 MPa, which was equal to the base metal in the as-cast condition. The UTS was increased by 60 MPa after annealing at 370 °C for 6 h that was 85% of UTS of the base alloy.
Highlights
Al-Mg alloys with scandium additives have been actively developed and are already used in industry
Hot cracking susceptibility depends on the value of the effective solidification range (ESR), the strength, and the plasticity in this range [6,7,8]
The production of a good quality weld depends on the power of the pulse and its duration, the frequency of pulses, and welding rate, the determination of the degree of overlap of the single welds formed by individual pulses of a laser beam, as well as the size of the area of a focused beam, and the shape of pulse
Summary
Al-Mg alloys with scandium additives have been actively developed and are already used in industry. Scandium greatly increases the yield stress (YS) of such alloys and, their strength due to the formation of the Al3 Sc nanoparticle phase, which retains the semi-finished deformed structure, even after annealing at temperatures above 300 ◦ C [1,2,3]. Al-Mg alloys are the weldable aluminum alloys They have high hot cracking susceptibility during argon-arc welding and high gas porosity after gas welding [4,5]. Increasing the magnesium content to more than 6% significantly decreased the formation of hot cracks [6,7,8]. Another way of decreasing hot cracking is grain refining
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