– Effect of phosphorus grain boundary segregation on intergranular fracture
? Introduction, experiment, results and discussion, summary
2020/4/15
Outline (2)
? Introduction, experiment, results and discussion, summary
– Effect of phosphorus grain boundary segregation on intergranular fracture
? Introduction, experiment, results and discussion, summary
2.25Cr1Mo 钢中磷的平衡及应力引 起的非平衡晶界偏聚
Equilibrium and Stress-induced NonEquilibrium Grain Boundary Segregations
of Phosphorus in a 2.25Cr1Mo Steel
Song Shenhua
2020/4/15
? Equilibrium grain boundary segregation
– Segregation of phosphorus and molybdenum
? Introduction, experiment, results and discussion, summary
– Relationship between phosphorus boundary concentration and ductile-to-brittle transition temperature (DBTT)
Preface (1)
Grain boundary segregation (GS)
2020/4/15
Preface (2)
Effects of grain boundary segregation on the properties of materials
Mechanical, corrosion, electrical, and magnetic properties
1?
CIg
?
C
g J
? Gi
RT ?,
?i ? I , M ?
? ? ? GI
?
?
G
0 I
? ? IM
CMeq ? CMg
(Guttmann, 1975)
? ? ? GM ? ? GM0 ? ? IM
CIeq
?
C
g I
C eq i
1? Cieq
?
Ci?,
?i ? I , M ?
erfc(x) = 1 – erf(x)
2020/4/15
(McLean, 1957)
Equilibrium grain boundary segregation (3)
concentration
Thermal equilibrium concentration
Applied stress
2020/4/15
2.25Cr1Mo steel
Outline (1)
? Equilibrium grain boundary segregation
– Segregation of phosphorus and molybdenum
? Introduction, experiment, results and discussion, summary
2020/4/15
(Seah, 1977)
Equilibrium grain boundary segregation (2)
Segregation kinetics
C ?t
Ceq
???CC??00???
1?
exp
? 4Dt
? ?
?
22d
2
??
?erfc ?
???
4Dt ?
?
2 2
d
2
???
? 2 ? Ceq Cg
? Stress-induced non-equilibrium grain boundary
segregation – Introduction, experiment, results and discussion,
summary
? Conclusions
2020/4/15
Outline (1)
Preface (3)
GS
Thermally induced NEGS
2020/4/15
Stress induced NEGS
EGS
NEGS
Irradiation induced NEGS
……
NEGS induced by high
temperature deformation
Preface (4)
– Relationship between phosphorus boundary concentration and ductile-to-brittle transition temperature (DBTT)
? Introduction, experiment, results and discussion, summary
2020/4/15
Equilibrium grain boundary segregation (1)
Segregation thermodynamics
Ceq ? Cg exp ?? G RT ?
1? Ceq 1 ? Cg
(McLean, 1957)
? Cieq
1?
C
eq I
?
CMeq
?
Cig
exp
e.g., in structural materials, such as steel and Ni alloys Segregation of detrimental elements such as S, P, Sn, and Sb – decreasing the grain boundary cohesion – grain boundary weakening Segregation of beneficial elements such as B, C and Be – increasing the grain boundary cohesion – grain boundary strenthening