Forgeabilité des aciers inoxydables austéno-ferritiques

tel-00672279, version 1 - 21 Feb 2012
Chapter III. HOT CRACKING RESISTANCE 89
III.7.2 Results
Figure III.49 gives the results obtained on the D1bis_W microstructure. The results from the D1_W
microstructure are also reported in Figure III.49. The relationship between the total specific work of
fracture and the ligament length follows the expected linear behaviour.
w tot (kJ.m -2 )
800
700
600
500
400
300
200
100
0
D1_W
D1bis_W
y = 13.5x + 198.53
R² = 0.9528
y = 13.329x + 51.238
R² = 0.9527
0 4 8 12 16 20 24 28 32 36 40
l 0 (mm)
Figure III.49. Variation of the specific work of fracture as a function of the ligament length for separation
of the essential work of fracture. Comparison between D1_W and D1bis_W microstructures at 1050°C.
The plane stress specific work of fracture at 1050°C is equal to 199 kJ.m - ² and 51 kJ.m - ² for the micro-
structures D1_W and D1bis_W, respectively. It means that at 1050°C, D1_W is almost four times
more resistant to ductile tearing than D1bis_W.
Typical fracture profiles are shown in Figure III.50. Both microstructures, D1bis_W and D1_W exhibit
an irregular profile along the ligament. D1bis_W and D1_W differ by their equivalent strain to fracture:
the arrows in Figure III.50 emphasize this difference.
1 mm
a) b)
1 mm
Figure III.50. Fracture micrographs and profiles of the broken DENT at 1050°C; a) D1_W (l0=35mm); b)
D1bis_W (l0=35mm).