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1、* Equilibrium and Stress-induced Non- Equilibrium Grain Boundary Segregations of Phosphorus in a 2.25Cr1Mo Steel Song Shenhua 2.25Cr1Mo钢中磷的平衡及应力引 起的非平衡晶界偏聚 * Preface (1) Grain boundary segregation (GS) Effects of grain boundary segregation on the properties of materials Mechanical, corrosion, electr
2、ical, and magnetic properties 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 c
3、ohesion grain boundary strenthening Preface (2) * Preface (3) GS EGS NEGS NEGS induced by high temperature deformation Stress induced NEGS Irradiation induced NEGS Thermally induced NEGS * Preface (4) 2.25Cr1Mo steel Applied stress * Outline (1) Equilibrium grain boundary segregation Segregation of
4、phosphorus and molybdenum Introduction, experiment, results and discussion, summary Relationship between phosphorus boundary concentration and ductile-to-brittle transition temperature (DBTT) Introduction, experiment, results and discussion, summary Effect of phosphorus grain boundary segregation on
5、 intergranular fracture Introduction, experiment, results and discussion, summary * Outline (2) Stress-induced non-equilibrium grain boundary segregation Introduction, experiment, results and discussion, summary Conclusions * Outline (1) Equilibrium grain boundary segregation Segregation of phosphor
6、us and molybdenum Introduction, experiment, results and discussion, summary Relationship between phosphorus boundary concentration and ductile-to-brittle transition temperature (DBTT) Introduction, experiment, results and discussion, summary Effect of phosphorus grain boundary segregation on intergr
7、anular fracture Introduction, experiment, results and discussion, summary * Equilibrium grain boundary segregation (1) (McLean, 1957) (Seah, 1977) (Guttmann, 1975) Segregation thermodynamics * Equilibrium grain boundary segregation (2) Segregation kinetics (McLean, 1957) erfc(x) = 1 erf(x) * Equilib
8、rium grain boundary segregation (3) Ageing time Solute boundary concentration Thermal equilibrium concentration * Outline Equilibrium grain boundary segregation Segregation of phosphorus and molybdenum Introduction, experiment, results and discussion, summary Relationship between phosphorus boundary
9、 concentration and ductile-to-brittle transition temperature (DBTT) Introduction, experiment, results and discussion, summary Effect of phosphorus grain boundary segregation on intergranular fracture Introduction, experiment, results and discussion, summary * Introduction P-Mo interaction Weak or st
10、rong? * Experiment (1) Ingot Plate Block 2 Normalization Austenization Temper Hot rolling Vacuum induction Raw material Cutting Block 1 Sample processing and pretreatment * Experiment (2) AES Pretreated samples Experimental procedure Aging at different temperatures for different times and quenching
11、Boundary concentration Fraction of Intergranular fracture SEM Impact test Machining DBTT Hardness test Metallographic analysis Hardness Grain zize * 92050min Time Temperature 98030min 6502h Air cooling Oil quenching Water quenching (Normalization) (Austenization) (Termper) (Aging under different str
12、esses for different time) Quenching 520 Heat treatment procedure Experiment (3) 520 480 Water quenching 560 (Ageing) * Experiment (4) Auger electron spectrometerAuger specimen * Experiment (5) AES scanning position Fracture surface of AES specimen * Results and discussion (1) Typical AES spectra * R
13、esults and discussion (2) Ageing time Solute boundary concentration Thermal equilibrium concentration 480oC * Results and discussion (3) 520oC560oC * Results and discussion (4) Equilibrium boundary concentrations at different temperatures Segregation energies at different temperatures * Results and
14、discussion (5) P-Mo interaction is very week * Summary The interaction between phosphorus and molybdenum is very weak. The segregation enthalpies of phosphorus and molybdenum are about 38 and 17 kJmol-1, respectively. The segregation entropies of phosphorus and molybdenum are both about 0. * * Outli
15、ne (1) 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) Introduction, experiment, results and discussio
16、n, summary Effect of phosphorus grain boundary segregation on intergranular fracture Introduction, experiment, results and discussion, summary * Introduction (1) -150 -100-50050 0 20 40 60 Impacct temperature % ductile fracture 80 100 DBTT * Introduction (2) DBTT Grain sizeHardness P boundary concentration * Experiment Pretreated samples Experimental procedure Aging at different temperatures for different
