PSI - Issue 59

Sviatoslav Motrunich et al. / Procedia Structural Integrity 59 (2024) 58–65 Sviatoslav Motrunich et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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5

The chemical composition analysis of the ingot metal at top, middle and bottom parts is presented in Table 2. The distribution of alloying elements along the length of the ingot is uniform and corresponds to the grade composition.

a b Fig. 4. Internal defect examination: (a) A-scan results of nondestructive testing; (b) macrostructure of obtained ingot.

Table 2. Chemical composition of obtained ingot. Ti-6Al-7Nb alloy

Chemical elements, % weight.

Nb 6.8 6.7 6.7

Ta

Fe

C

H

O

N

А1 6.2 6.3 6.2

0.01 0.01 0.01

0.09 0.10 0.08

0.01 0.01 0.01

0.005

0.11

0.012

Top Middle Bottom

Obtained ingot

UNS R56700 (Standard requirements) 5.6-6.6

6.5-7.5

<0.5 <0.25 <0.03 <0.05 <0.20 <0.05

A crucial quality criterion for titanium alloy ingots is the absence of non-metallic inclusions, particularly or titanium nitrides. As shows microstructure study of the metal is the same along the entire length of the ingot and is characterized by crystals close to equiaxed in shape. Sections of the columnar structure are absent. So, when titanium is remelted using electron beam melting technology with an intermediate capacity, thermal and physico chemical conditions are created that ensure the removal of the above-mentioned inclusions.

a

b

c

Fig. 5. Microstructure of cast metal of Ti-6Al-7Nb titanium alloy ingot.

The general appearance of the microstructure of the obtained Ti-6Al-7Nb alloy by the developed EBCHM technology is shown in Fig. 5. The metal of the Ti-6Al-7Nb titanium alloy consists of equiaxed grains with a size of 100- 500 μm. Formation of a homogeneous structure is observed, with no signs of zonal liquation (Fig. 5.a). This testifies of good technology parameters selection of EBCHM ingot production. The boundaries of the grains are framed by an α -phase layers , sometimes continuous, sometimes fragmented. The thickness of the α -phase layers is