Crack Paths 2006

10-5

2022T851Ambient air

2022T851cold air

10-6

2022T851vacuum300K V 223

10-7

10-8

10-9

10-10

10-11

4 6 8 10

30 50

'K(MPa.m1/2)

Figure 5: Crack propagation rates in air and high vacuumat 300Kand 223K

for the 2022 peakaged alloy

10-5

2024AT351vacuum300K

2022 T351vacuum300K

10-6

2024AT351air 223K

2022 T351air 223K

2024AT351vacuum223K

10-7

2022 T351Vacuum223K

10-8

10-9

10-10

10-11

4 6

8 10

30

' K(MPam1/2)

Figure 6: Crystallographic crack propagation in naturally aged 2024Aand 2022 alloys in cold

dry air and in high vacuum.