PSI - Issue 50

Aleksandr Malikov et al. / Procedia Structural Integrity 50 (2023) 170–177 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

172

3

These alloys are a solid solution of α - Al with alloying elements. 1420 alloy contains a hardening phase δʹ(Al 3 Li), a metastable phase S1(Al 2 MgLi), as well as sp herical dispersed particles of the β ′ (Al 3 Zr) phase. The addition of Zr to Al – Mg – Li alloys is effective in improving toughness and stress corrosion resistance, which is associated with the formation of the β'(Al 3 Zr) phase. The β' phase also has the function of heterogeneous nucleation for the strengthening phase δ' with the formation of a complex precipitate β'/δ formed after the aging process. In the AMg6 alloy, in addition to the main phase - the α - Al solid solution, there are dispersed particles of the β (Al 3 Mg 2 ) and Al 6 Mn phases, which are the decomposition products of the solid solution during crystallization. Chemical composition and mechanical characteristics alloy are presented in tables 1 and 2.

Table 1. Chemical composition (%, wt). Alloy and system Mg Li

Zn

Zr

Mn

Ti Fe

1420 Al-Mg-Li

5,8-6,2 1,8-2,2 0.05 0,01 0,1-0,25 - -

AMg6 Al-Mg-Mn 5,8-6,2 -

0,02 -

0,5-0,8 0,020,4

Table 2 presents the main mechanical properties, where σ UTS is ultimate tensile strength , σ YS is yield strength, and δ is elongation, ρ density .

Table 2. The mechanical property. Alloy and system ρ, g/cm 3 σ

σys 2 , MPa δ , %

в , MPa

1420 Al-Mg-Li

2,5

440-450 280 315-375 190

7-10

AMg6 Al-Mg-Mn 2,65

10

Aviation 1420 aluminum alloy of the Al-Mg-Li system in the form of a sheet of 1.4 mm thick, was purchased at the Kamensk-Ural Metallurgical Plant (JSC KUMZ), as well as welding wire AMg6 of the Al-Mg-Mn system with a diameter of 1 mm. To carry out the expe rimental work on laser welding, the laser complex “Siberia - 1” was used, which includes a CO 2 laser with a power of up to 8 kW, developed at ITAM SB RAS, a portal-type technological table, and a CNC control system Malikov et al.(2019). Transmission diffraction studies of the sample were carried out using synchrotron radiation with a wavelength of 0.3685 Å at the station "Hard X -ray diffractometry" of the 4th channel of the VEPP-3 storage ring in the Laue geometry Ancharov et al. (2001) at the Institute of Nuclear Physics named after G.I. Budker SB RAS. Synchrotron radiation has the following main advantages: hard X-ray; high beam brightness more than 10 6 photons/sec higher than X-ray tube radiation; detection of lithium-containing phases smaller than 50 nm; determination of the phase composition in the bulk of the material; small beam area allows for local analysis of the volume of the material; does not require complex sample preparation. The use of synchrotron radiation makes it possible to accurately determine lithium-containing phases. It should be noted that lithium, which is included in the composition of the initial material in the form of lithium-containing phases, cannot be detected by EDX analysis with scanning electron microscopy and EDAX analysis with transmission electron microscopy due to the smallness of the characteristic X ray signal from light elements. To study the phase composition of the alloy and the center of the weld, a beam of monochromatized synchrotron radiation with a cross section of 100*400 µm was used. The resulting diffraction rings were integrated over the radius and recalculated for λ= 1.5406 Å. The measurement was carried out at 7 points - in the alloy, the heat affected zone, the melting zone. The phase analysis was determined using the PDF-4 crystallographic database. Measurement points are shown in Figure 1. Points 1, 6 are measurement zones in the alloy, points 2, 5 are in the heat affected zone (HAZ), and points 3, 4 are in the weld fusion zone.