20172材料科学基础英文版.pptx

2024/4/20 周六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钢中磷的平衡及应力引起的非平衡晶界偏聚起的非平衡晶界偏聚2024/4/20 周六Preface(1)Grain boundary segregation(GS)Effects of grain boundary segregation on the properties of materials Mechanical,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)2024/4/20 周六Preface(3)GSEGSNEGS NEGS induced by high temperature deformationStress induced NEGSIrradiation induced NEGSThermally induced NEGS2024/4/20 周六Preface(4)2.25Cr1Mo steelApplied stress2024/4/20 周六Outline(1)Equilibrium grain boundary segregationSegregation of phosphorus and molybdenumIntroduction,experiment,results and discussion,summaryRelationship between phosphorus boundary concentration and ductile-to-brittle transition temperature(DBTT)Introduction,experiment,results and discussion,summaryEffect of phosphorus grain boundary segregation on intergranular fractureIntroduction,experiment,results and discussion,summary2024/4/20 周六Outline(2)Stress-induced non-equilibrium grain boundary segregationIntroduction,experiment,results and discussion,summaryConclusions2024/4/20 周六Outline(1)Equilibrium grain boundary segregationSegregation of phosphorus and molybdenumIntroduction,experiment,results and discussion,summaryRelationship between phosphorus boundary concentration and ductile-to-brittle transition temperature(DBTT)Introduction,experiment,results and discussion,summaryEffect of phosphorus grain boundary segregation on intergranular fractureIntroduction,experiment,results and discussion,summary2024/4/20 周六Equilibrium grain boundary segregation(1)(McLean,1957)(Seah,1977)(Guttmann,1975)Segregation thermodynamics2024/4/20 周六Equilibrium grain boundary segregation(2)Segregation kinetics(McLean,1957)erfc(x)=1 erf(x)2024/4/20 周六Equilibrium grain boundary segregation(3)Ageing timeSolute boundary concentrationThermal equilibrium concentration2024/4/20 周六OutlineEquilibrium grain boundary segregationSegregation of phosphorus and molybdenumIntroduction,experiment,results and discussion,summaryRelationship between phosphorus boundary concentration and ductile-to-brittle transition temperature(DBTT)Introduction,experiment,results and discussion,summaryEffect of phosphorus grain boundary segregation on intergranular fractureIntroduction,experiment,results and discussion,summary2024/4/20 周六IntroductionP-Mo interactionWeak or strong?2024/4/20 周六Experiment(1)IngotPlateBlock 2NormalizationAustenizationTemperHot rollingVacuum inductionRaw materialCuttingBlock 1Sample processing and pretreatment2024/4/20 周六Experiment(2)AESPretreated samplesExperimental procedureAging at different temperatures for different times and quenchingBoundary concentrationFraction of Intergranular fractureSEM Impact testMachiningDBTTHardness testMetallographic analysis HardnessGrain zize2024/4/20 周六92050minTimeTemperature98030min6502hAir coolingOil quenchingWater quenching(Normalization)(Austenization)(Termper)(Aging under different stresses for different time)Quenching520Heat treatment procedureExperiment(3)520480Water quenching560(Ageing)2024/4/20 周六Experiment(4)Auger electron spectrometerAuger specimen2024/4/20 周六Experiment(5)AES scanning positionFracture surface of AES specimen2024/4/20 周六Results and discussion(1)Typical AES spectra2024/4/20 周六Results and discussion(2)Ageing timeSolute boundary concentrationThermal equilibrium concentration480oC2024/4/20 周六Results and discussion(3)520oC560oC2024/4/20 周六Results and discussion(4)Equilibrium boundary concentrations at different temperaturesSegregation energies at different temperatures2024/4/20 周六Results and discussion(5)P-Mo interaction is very week2024/4/20 周六SummaryThe 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 0.2024/4/20 周六2024/4/20 周六Outline(1)Equilibrium grain boundary segregationSegregation of phosphorus and molybdenumIntroduction,experiment,results and discussion,summaryRelationship between phosphorus boundary concentration and ductile-to-brittle transition temperature(DBTT)Introduction,experiment,results and discussion,summaryEffect of phosphorus grain boundary segregation on intergranular fractureIntroduction,experiment,results and discussion,summary2024/4/20 周六Introduction(1)-150-100-500500204060Impacct temperature%ductile fracture80100DBTT2024/4/20 周六Introduction(2)DBTTGrain sizeHardnessP boundary concentration2024/4/20 周六ExperimentPretreated samplesExperimental procedureAging at different temperatures for different times and quenchingBoundary concentrationFraction of Intergranular fractureSEM Impact testMachiningDBTTHardness testMetallographic analysis HardnessMicrostructure,Grain sizeAES2024/4/20 周六Results and discussion(1)A:650oC2h B:560oC100hC:480oC500hD:480oC800hE:480oC1200h 2024/4/20 周六Results and discussion(2)650oC2h480oC1200h 100 m(a)100 m(b)2024/4/20 周六Results and discussion(3)R-square=0.9972024/4/20 周六Results and discussion(4)Temperature-time embrittlement diagram2024/4/20 周六SummaryThere is a linear relationship between DBTT and phosphorus boundary concentration.A temperature-time embrittlement diagram was established.From the diagram,the DBTT of the material aged for any time at any temperature can be predicted.2024/4/20 周六2024/4/20 周六Outline(1)Equilibrium grain boundary segregationSegregation of phosphorus and molybdenumIntroduction,experiment,results and discussion,summaryRelationship between phosphorus boundary concentration and ductile-to-brittle transition temperature(DBTT)Introduction,experiment,results and discussion,summaryEffect of phosphorus grain boundary segregation on intergranular fractureIntroduction,experiment,results and discussion,summary2024/4/20 周六Introduction(1)2024/4/20 周六Introduction(2)Does low temperature facilitate intergranular fracture?Christiens results in 17-4 PH martensitic stainless steel:The specimen experienced ductile fracture,intergranular fracture,cleavage fracture when impact-fractured from 300oC to-196oC.(Christien,2003)2024/4/20 周六ExperimentPretreated samplesExperimental procedureAging at different temperatures for different times and quenchingBoundary concentrationFraction of Intergranular fractureSEM Impact testMachiningDBTTHardness testMetallographic analysis HardnessMicrostructure,Grain sizeAES2024/4/20 周六Results and discussion(1)480oC1200h 650oC2h Intergranular fracture is not observed at all test temperatures 2024/4/20 周六Results and discussion(2)StressTemperatureOIntergranular fracture stressCleavage fracture stressYield strengthTcTaTb2024/4/20 周六SummaryPhosphorus grain boundary segregation facilitates intergranular fracture.The specimen experienced ductile fracture,intergranular fracture,and cleavage fracture when impact-fractured from high to low temperature.2024/4/20 周六2024/4/20 周六OutlineStress-induced non-equilibrium grain boundary segregationIntroduction,experiment,results and discussion,summaryConclusions2024/4/20 周六Introduction(1)343 MPa(Shinoda and Nakamura,1981)(Misra,1996)2024/4/20 周六Introduction(2)Diffusional creepGrain interiorGrain boundarySolute atoms2024/4/20 周六Introduction(3)Xus modelGrain interiorGrain boundarySolute atomsVacancyVacancy-solute complex2024/4/20 周六Experiment(1)Creep test Pretreated samplesExperimental procedureAgeing without stress for 1000 h and quenchingCreep curvesStress ageingMachiningSegregation kineticsTensile testYield strengthAES analysis2024/4/20 周六920 50minTimeTemperature980 30min6502hAir coolingOil quenchingWater quenching(Normalization)(Austenization)(Termper)(Aging under different stresses for different time)Quenching520Heat treatment procedureExperiment(2)520480Water quenching(Aging without stress for 1000h)5602024/4/20 周六Experiment(3)2024/4/20 周六Results and discussion(1)Yield strength:462 MPa 2024/4/20 周六Results and discussion(2)Creep curves and segregation kinetics40 MPa40 MPa200 MPa200 MPa350 MPa350 MPa2024/4/20 周六Results and discussion(3)Stress ageing timeP boundary concentrationComplex effectCreep effectCombined effectSegregation kinetics under high stress2024/4/20 周六Results and discussion(4)Grain boundary is deformed preferentiallyDeformation can produce vacancy()Strain hardeningDeformation spreads to grain interiorSegregation kinetics under medium stress2024/4/20 周六SummaryStress can induce different kinds of segregation kinetics.Elastic deformation and creep deformation can both affect phosphorus segregation kinetics.2024/4/20 周六2024/4/20 周六ConclusionsThe interaction between phosphorus and molybdenum is very weak.There is a linear relationship between DBTT and phosphorus boundary concentration.A temperature-time embrittlement diagram was established.From the diagram,the DBTT of the material aged for any time at any temperature can be predicted.Phosphorus grain boundary segregation facilitates intergranular fracture.The specimen experienced ductile fracture,intergranular fracture,and cleavage fracture when impact-fractured from high to low temperature.Elastic deformation and creep deformation can both affect phosphorus segregation kinetics during stress ageing.2024/4/20 周六