PSI - Issue 50

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

175

6

p -d / (Al

3 Li)

/ (Al

q - S (Al 2 MgLi)

q - S (Al 2 MgLi)

3 Li)

p -d

Al(220)

Al(220)

· - (Al 3 Mg 2 )

· - (Al 3 Mg 2 )

Al(111) Al(200)

Al(111) Al(200)

30

p

p

qq

p p

p

HAZ Alloy

HAZ Alloy

p

25

·

p

·

·

q

·

·

·

qq

·

q

p

p

·

·

·

p p

20

q

·

·

·

·

q

·

·

·

·

qq

p

p

·

10 Intensity (counts) 15

Intensity (counts)

·

p p

q

·

Weld

Weld

·

·

·

·

p

·

p

qq

·

·

·

q

q ·

·

·

· q

·

·

·

·

p

qq

p

p

·

p

HAZ Alloy

HAZ Alloy

5

p p

p

q

p

p p

q

p

0

10

20

30

40

50

60

70

10

20

30

40

50

60

70

2 Q ( degree)

2 Q ( degree)

p

a)

b)

Fig. 4. X-ray patterns (in transmission) of a sample with a welded joint (a), a sample with a welded joint after post heat treatment (b).

Fig. 4a (points 1, 6) shows that in the diffraction patterns of the original alloy, in addition to intense reflections of the Al phase, there are mainly reflections of the strengthening phase δ'(Al 3 Li) and a weak reflection of the S1(Al 2 MgLi) phase. In the melting zone and the HAZ of the weld (Fig. 4a (points 2,3,4,5), there are mainly intense reflections of the  (Al 3 Mg 2 ) and S1(Al 2 MgLi) phases. It should be noted that the 1420 alloy contains the strengthening phase δʹ(Al 3 Li), the metastable phase S1 (Al 2 MgLi), as well as spherical dispersed particles of the β′(Al 3 Zr) phase. In the AMg6 alloy, in addition to the main phase, the α -Al solid solution, there are dispersed partic les of the β (Al 3 Mg 2 ) and Al 6 Mn phases, which are the decomposition products of the solid solution during crystallization. It can be assumed that during laser welding 1420 alloy with AMg6 wire, as a result of melting and subsequent solidification in the weld, the formation of mainly  (Al 3 Mg 2 ) and S1(Al 2 MgLi) phases occurred; the strengthening phase δ′ (Al 3 Li) is absent. After the procedure of hardening, plastic deformation and artificial aging in the alloy and in the weld, mainly reflections of the hardeni ng phase δ′ (Al3Li); a small number of reflections S 1 (Al2MgLi) and  (Al3Mg2) were noted. The results of the analysis of the change in the phase state during laser welding with wire and post-processing are summarized in Figure 5.

Fig. 5. Scheme of structural-phase transformations of the alloy and weld before and after post weld heat treatment.

The main phases, that directly affect the mechanical characteristics are singled out. The evolution of the phase composition of the weld can be represented as follows: weld ► post weld heat treatment ά Al+  + S 1 άAl+ δ '+S 1 + 

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