PSI - Issue 46

David Liović et al. / Procedia Structural Integrity 46 (2023) 42 – 48 D. Liovi ć et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 4. Surface porosity of cubic specimens for different combinations of process parameters

Table 3. SLM Ti6Al4V alloy monotonic properties data comparison. References P / v Conditions

R p0.2 , MPa

Porosity, %

Orientation

R m , MPa

A , %

200 W / 200 mm/s 75 W / 600 mm/s

1035 ± 29

Edwards et al. (2014)

As-built

Horizontal

910 ± 9.9

3.3 ± 0.76

-

Pal et al. (2020)

As-built

-

1420

1230

5,6 ± 1

0.55

200 W / - 200 W / -

850°C for 1 hour, FC

Horizontal

1018

982

1,3

-

Hartunian et al. (2018)

850°C for 1 hour, FC

Vertical

872

868

0.98

-

200 W / 1250 mm/s 195 W / 225 mm/s

Kasperovich et al. (2015)

700°C for 1 hour, FC

Vertical

1051

1115

11.3

0.077

Combined heat treatments

-

870 ± 15

990±15

11 ± 0.5

0.3

Facchini et al. (2010)

- -

890°C for 2 hours, FC 890°C for 2 hours, FC

Horizontal

996 ± 10 998 ± 14

973±8 946±7

3 ± 0.4

< 1% < 1%

Cain et al. (2015)

Vertical

6 ± 2

250 W / 1600 mm/s

12.84 ± 1.36

Vrancken et al. (2012)

850°C for 2 hours, FC

Horizontal

955 ± 6

1004±6

≈ 0%

If the monotonic mechanical properties previously stated by Cain et al. (2015) in Tab. 3 are observed, it is noticeable that even a higher amount of elongation at break values can be achieved for vertically oriented tensile test specimens, which is quite unusual for the additively manufactured materials. However, one possible explanation for such behavior is the orientation of prior β grain boundaries, which in this case are in larger extent parallel to the build direction. Since in that case tensile force also acts parallel to the build direction, grain boundaries in larger extent are not subjected to most critical tensile crack opening mode (Mode 1 failure). This can eventually lead to an increase in elongation at break values of vertically oriented specimens during SLM process, compared to horizontally oriented specimens.