鈦的力學(xué)性質(zhì)及氫脆現(xiàn)象的分子動(dòng)力學(xué)研究.pdf

1、復(fù)旦大學(xué)碩士學(xué)位論文鈦的力學(xué)性質(zhì)及氫脆現(xiàn)象的分子動(dòng)力學(xué)研究姓名：白顯明申請(qǐng)學(xué)位級(jí)別：碩士專(zhuān)業(yè)：物理電子學(xué)與光電子學(xué)指導(dǎo)教師：陸明張強(qiáng)基2000.5.1；【!上擎Ⅲ士掌位論文鈦的力掌性質(zhì)及氨脆象的#子動(dòng)力學(xué)H究TheMechanicalPropertiesofTitaniumandThePhenomenaofHydrogenEmbrittlementinTitanium：AMolecularDynamicsStudyAbstractApp

2、lyingMolecularDynamics(MD)tothestudyofthemechanicalpropertiesoftitaniumandthephenomenaofhydrogenembrittlementintitanium，followingworkshavebeenperformed：Thetemperature—dependentEmbedded—atomMethod(EAM)functionsoftitaniuma

3、redeterminedempiricallybyfittingtothelatticeconstants，elasticconstan|sandsublimationenergiesatvarioustemperaturesUnfortunatelytheseEAMfunctionsarelocallyanalyticalattheequilibriumsites，andtheyarenotappropriatetodescribet

4、hesituationswhentheatomsarefarawayfromtheirequilibriumsitesorthescalesoflatticeconstantschangelargelyAlternativelyamoreappropriateEAMpotentialfunctionisdeterminedbyfittingtotheROSEuniversalequationTheequationisafunctiono

5、fthelatticeconstant，sothedrawbackofthefirstmethodiseliminatedTheEAMfunctionderivedfromitisusedinthelatterMDstudyandtheresultsarefairlygoodTheatomiclevelmechanicalpropertiesofTitaniumunderuniaxialstressarestudiedwiththePa

6、rrinello—RahmanMDformalismTheresultsdemonstratethatwhentheexternalpressureislowerthanthecriticalpressure，thereisalinearrelationshipbetweenthepressureandtheelongationWhenthetemperatureisat300KthecalculatedYoung’smodulusis

7、29x10”P(pán)aabouttwicetimes∞theexperimentaldataItisreasonablebecausetherearenodefectsinourmodelWhenthepressureishigherthanthecriticalpressure，thelinearrelationshipdisappearsSimilarinvestigationsareperformedwhenthetemperature

8、isat500Kand700KTheresultsshowthattheYoung’smodulus，thecriticalpressureandthefracturepressuredecreaseslightlywhenthetemperatureincreasesTheseresultsdemonstratethattitaniumiseasiertobeelongatedandfracturewhenthetemperature

9、ishigherThehydrogenEmbritfiementintitaniumisalsostudiedwithMDTheEAMpotentialfunctionofhydrogenisdeterminedbyfittingtothehydrogenmigrationenergyandtheheatofsolutionintitaniumOuratomiclevelcalculationdemonstratesthatthehyd

10、rogentitaniumsystemiseasiertofracturethantitanium，whichiscalledhydrogenembrittlementOurinvestigationshowsthatthelargescalediffusionofhydrogenatomsintitaniuminducesthe”hydrogenenhancedlocalplasticity(HELP)”mechanismThisme