Nb基超高溫合金母合金錠的制備及定向凝固用坩堝的選擇.pdf

1、西北工業(yè)大學碩士學位論文Nb基超高溫合金母合金錠的制備及定向凝固用坩堝的選擇姓名：武興君申請學位級別：碩士專業(yè)：材料加工工程指導教師：郭喜平20060301ABSTRACT㈧obium—basedalloyshavehi醵meltingpoints，relativelylowdensitiesandexcellentmechanicalpropertiesincludinghi酶temperature$瓣嶷g遺，loomtemgerat

2、ljrefracluretougkness，豁theyhave蟊燃thefocusofrecentstudies。TheyhavehighpotemialforthefutureaerospaceapplicationsThecompositionsystems&niobiumbasedalloyshavebeendesignedinthispaperTheingotswefeproducedbyVacuumselfconsumable

3、arcmeltingTheare—meltedmicrostrueturewasexandned鍵感ngallopticalmicroscope(OMXsearuingelectronmicroscope(SEM)筑靜瓣檄vdth鼗energydispersiveXrayspectroscope(EDX)。到按cruciblesfordirectionalsolidificationwereselectedandexaminedL琦ou

4、ghexperimentsTheresultsofSEMindicatedthatthemierostrueturewasuniformandconsistedoflargeamOuntSofeute確emidrOstructumsXraydiffractionanalysisshowedthatthisaremeltedmicrostnietm罄刪s醚ofniobiumsolidsolutieaftrb瓣andniobiumsific

5、idesfNbsSidNt廷Si)。NbsSi3基鑫s箍orderedstr燃aeTheanalysisofselectedareaelectrondiffractionpatternrevcaledthattherewerecertainorientationrelationshipsbetweenNbsSi3andNbss，Thatwas[010】／／[1351。Thesamplesofniobiumbasedalloyswerer

6、emeltedingraphitecruciblesgraphitebasedSiCcoated。：eraeiblesgraNitebased韙f冬c出atedcruciblesandBNertmibte&For蘸罄瓣phite掰端瓶theslhfa麟oftire劫融：has囂鏹i癱燃of509rareactionlayer瓣鼢restdtantprodnetion獬mainly翻carbidesoftitaniumandniobium

7、，ThecrosslikecarbidesarealSOfoundilinsidethealloybarsBecausethereactionordecompositionofSiCcoating，thereactionandproductionWaSnearlythesa掰eas燃isthepuregraphitecrucibles。Becausethepreparationtechnologyof珞酶coatingWaSnotwel

8、ldevelolx／dtheY赫eoatinghadnotprevented瓣cruciblefromreactionwi爨themeltedalloyThereactionoftheNiobiumbasedalloywasmuchmoreseverewhenremeltedinaBNcruci；bleandtherewelemanyeroseholesintheOUle：regionofthealloybars，Thethicknes

9、softhereactionlayerisabout60pm，andthereweremanycavitiesfoundinsidethealloyThereactionproduct誕theBNcat|cibleismainly&nitrideofthetitaniumandniobium，’Keywords：niobiumbasedultrahightemperaturematerials，arcmelting，directiona