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钢的回火脆性动力学的实验研究.pdf

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http://www.paper.edu.cn ExperimentalStudyonTemper EmbrittlementDynamics inIndustrialSteel LiLiQingfenLiErbaoLiu CollegeofMechanicalandElectricalEngineering HarbinEngineeringUniversity Harbin,P.R.China150001 lili_heu@yahoo.com.cnqingfli@yahoo.com.cnliutong_05@163.com Abstract Temperembrittlementdynamicswasexperimentallystudiedinanindustrialsteel 12Cr1MoV.Accordingtothenon-equilibriumgrain-boundarysegregation(NGS) kineticscurveofphosphorus,atsolutiontemperature1050°Cwithisothermalholding temperature540°C,aseriesofCharpyimpacttestswasperformedonspecimensof differentholding-time(0h,100h,500h,800h,i.e.atthesegregationprocess,the criticaltime,andthedesegregationprocessrespectively)inthetemperaturerange from-100°Cto20°C.Theductilitybrittlenesstransitiontemperature(DBTT)values weremeasuredandatemperembrittlementdynamicscurvewasobtained.Fracture morphologyandmicrostructureswereobservedbySEMandTEMrespectively. Resultsshowedthatoveragingappearedinthissteel.Thatisthedegreeof embrittlementincreasesfirstandthendecreaseswithisothermalagingtime,andthe peakofembrittlementappearsatabout500hour,i.e.atthecriticaltime. Non-equilibriumgrain-boundarysegregationmechanisminducedbycomplexof phosphor-vacanciescanprovideareasonableinterpretationtothedynamicsoftemper embrittlement. Keywords:Steels;temperembrittlement,grainboundariessegregation,ductility brittlenesstransitiontemperature(DBTT).. 1Introduction Reversetemperembrittlementwhichgenerallyappearsafterheatingorslowcoolinginthecritical temperaturerange(350-550°C)inlow-alloysteelsisacomplexmetallurgicalproblem.Common indicationsofembrittlementarethelossoftoughness,i.e.ashiftintheductiletobrittletransitionto highertemperatures,thefracturealonggrainboundariesandsegregationofimpuritiestograin boundaries. Thetheoryofmicro-segregationtograinboundarycanbedivideintotwoforms:equilibriumand non-equilibrium.McLean[1]andSeah[2]proposedthatembrittlementwasduetoequilibrium grain-boundarysegregation(EGS)ofsoluteelements.Somepreviousworks[3-5]i