2材料科学基础英文版课件_(4).ppt

*Equilibrium and Stress-induced Non-Equilibrium Grain Boundary Segregations of Phosphorus in a 2.25Cr1Mo SteelSong Shenhua2.25Cr1Mo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 materialsMechanical, corrosion, electrical, and magnetic propertiese.g., in structural materials, such as steel and Ni alloysSegregation of detrimental elements such as S, P, Sn, and Sb decreasing the grain boundary cohesion grain boundary weakeningSegregation of beneficial elements such as B, C and Be increasing the grain boundary cohesion grain boundary strentheningPreface (2)*Preface (3)GS EGSNEGSNEGS induced by high temperature deformationStress induced NEGSIrradiation induced NEGSThermally induced NEGS*Preface (4)2.25Cr1Mo steelApplied stress*Outline (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 discussion, summary Effect of phosphorus grain boundary segregation on 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 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 intergranular 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)*Equilibrium grain boundary segregation (3)Ageing timeSolute boundary concentrationThermal equilibrium concentration*Outline 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 discussion, summary Effect of phosphorus grain boundary segregation on intergranular fracture Introduction, experiment, results and discussion, summary*IntroductionP-Mo interactionWeak or strong?*Experiment (1)IngotPlate Block 2NormalizationAustenizationTemperHot rollingVacuum inductionRaw materialCuttingBlock 1Sample processing and pretreatment*Experiment (2)AESPretreated samplesExperimental procedureAging at different temperatures for different times and quenchingBoundary concentrationFraction of Intergranular fractureSEM Impact testMachiningDBTTHardness testMetallographic analysis HardnessGrain zize*920 50minTimeTemperature980 30min650 2hAir coolingOil quenchingWater quenching(Normalization)(Austenization)(Termper)(Aging under different stresses for different time)Quenching520Heat treatment procedureExperiment (3)520480Water quenching560(Ageing)*Experiment (4)Auger electron spectrometer Auger specimen*Experiment (5)AES scanning positionFracture surface of AES specimen*Results and discussion (1)Typical AES spectra*Results and discussion (2)Ageing timeSolute boundary concentrationThermal equilibrium concentration480oC*Results and discussion (3)520oC 560oC*Results and discussion (4)Equilibrium boundary concentrations at different temperaturesSegregation energies at different temperatures*Results and 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.*Outline (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 discussion, summary Effect of phosphorus grain boundary segregation on intergranular fracture Introduction, experiment, results and discussion, summary*Introduction (1)-150 -100 -50 0 500204060Impacct temperature% ductile fracture80100DBTT*Introduction (2)DBTTGrain size HardnessP boundary concentration*ExperimentPretreated samplesExperimental procedureAging at different temperatures for different times and qu