PSI - Issue 17

Petr Dymáček et al. / Procedia Structural Integrity 17 (2019) 427 –433 Author name / Structural Integrity Procedia 00 (2019) 000 – 0 0

432

6

100

1100 °C, 10 -6 s -1

80

M9 M1 M2 A1

60

40

Strength [MPa]

20

0

850

900

950

1000

1050

1100

Temperature rolling [°C]

(a)

420

240

600 °C, 10 -6 s -1

800 °C, 10 -6 s -1

220

400

M9 M1 M2 A1

M9 M1 M2 A1

200

380

180

360

160

340

140

Strength [MPa]

Strength [MPa]

320

120

100

300

850

900

950

1000

1050

1100

850

900

950

1000

1050

1100

Temperature rolling [°C]

Temperature rolling [°C]

(b) (c) Fig. 5. Strength of studied alloys depending on the rolling temperature (a) 1100 °C, (b) 800 °C, (c) 600 °C.

The average grain size dependence on the rolling temperature was correlated with strength at 1100 °C for M9 and A1 alloys in Fig. 6. The highest strength occurs in the case of largest grain size. This is in agreement with the creep behavior of polycrystalline materials since the grain boundaries act as an accelerator of creep deformation and damage.

120

100

1100 °C, 10 -6 s -1 M9 strength M9 avg. grain size

1100 °C, 10 -6 s -1 A1 strength A1 avg. grain size

100

80

40 Avg. grain size [ m m] 60 80

20 Avg. grain size [ m m] 40 60

Strength [MPa]

Strength [MPa]

20

0

0

850

900

950

1000

1050

1100

850

870

890

910

930

950

970

Temperature rolling [°C]

Temperature rolling [°C]

(a)

(b) Fig. 6. Strength and average grain size of (a) M9 and (b) A1 alloys depending on the rolling temperature.

The strength-ductility diagrams shown in Fig. 7 for M9 and A1 alloys show dramatic drop of ductility between 600 and 800 °C and also shows the differences in strength due to different rolling temperatures.