Carbon supersaturated plate Carbon diffusion into austenite and
Carbon supersaturated plate Carbon diffusion into austenite and carbide precipitation in ferrite Carbon diffusion into austenite Carbide precipitation from austenite UPPER BAINITE (High Temperature) LOWER BAINITE (Low Temperature)
0. 2 µm
with carbides
Carbide-free alloys wt %
1 µm
Very poor toughness!
50 µm
T-zero curves
50 µm
Impact Energy 70 60 0. 4 C-3 Mn-2 Si 0. 4 C-4 Ni -2 Si 0. 2 C-3 Mn-2 Si 50 40 30 20 10 0 -200 -100 0 Test temperature / °C 100 200
20 µm
Bainite Martensite Pearlite 0 200 400 600 800 1000 1200 kilocycles to Crack Initiation Yates, Jerath
Yates, Jerath
Advances in carbide-free bainitic steels 180 Fracture toughness / MPa √m 160 140 18 wt% Ni maraging steel 120 100 80 60 40 20 1000 QT 1500 2000 Ultimate tensile strength / MPa 2500
an apple weighs 1 Newton = 1 Pa 1 m
Cooking temperature? 180 to 220 °C
200 °C for 20 days 2. 5 GPa Caballero, Mateo & Bhadeshia
a g g a g 50 nm
g g a a a 20 nm
Low temperature transformation: 0. 25 T/Tm Fine microstructure: 20 nm thick plates Carbide-free Designed using theory alone Typical mechanical properties:
Very Strong, Low Temperature Bainite 180 Fracture toughness / MPa m 1/2 160 18 wt%Ni maraging steel 140 120 100 80 60 40 20 1000 QT 1500 2000 Ultimate tensile strength / 2500 MPa
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