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1、西北工业大学硕士学位论文随浸渗合金中的Mg含量增加，材料的热导率和膨胀系数均下降。组织中残留的少量孔隙，对于降低复合材料的热膨胀有一定的贡献。关键词:热控制材料，Si-Al复合材料，无压浸渗，热导率，热膨胀系数，复合材料凝固西北工业大学硕士学位论文ABSTRACTAnewadvancedthermalmanagementmaterialwithexcellentthermalproperties,whichcomposedAluminumwithhighvolumefractionofSilicon,wasobtainedinthisthesis.
2、Pressurelessinfiltration(PLI),developedinrecentyears,isanavailablemethodtoproduceMetalMatrixComposites(MMCs),anditischaracterizedbysimplifiedprocessandlowcosts.Inthethesis,61-81vol%Sip-AlcompositeswerepreparedbyAl-AlloysmeltinfiltrationintoSiparticlesporouspreformswithoutexter
3、nalpressure.Siparticlesporouspreformspreparation,spontaneousmeltinfiltrationprocess,solidificationofAl-SialloysmeltintheinterspacesamongSiparticles,microstructuresandthermalpropertiesofthecomposite,weresystematicallyinvestigatedinthework.Themainresultsareasfollows:1.Akindofvac
4、uumpressurelessinfiltrationequipment(VPI)wasdesignedandmadebyselves.ThesystemofVPIequipmentmainlyincludesvacuumchamber,heatingunit,worktablewithitsdriveunit,vacuumpumpingunit,gas-chargeunitandcontrolunit,etc.ThisequipmentwouldmeettheneedofA1orCumatrixcompositespreparedbypressu
5、relessinfiltrationorvacuuminfiltrationinahighvacuumorspecialatmosphere.2.Siparticlesporouspreforms~preparedbycoldisostaticpressingprocess(CIP).Itsaverageporosityisabout31.3%.3.HighvolumefractionSip-A]compositeswerefabricatedbyAl-alloymeltinfiltrationintoSiparticlesporousprefor
6、mswithoutexternalpressuresuccessfully.Itsthermalconductivityis94.8-128.7W/(m.K),itsthermalexpansioncoefficientis5.1-7.8XI0-'/K(50'C一100'C)anditsdensityislessthan2.5g/cm3respectively.4.TheprocessofAl-alloysmeltinfiltrationintoSipporouspreformswasinvestigatedItisnecessarythatthe
7、existenceofMginAl-alloysandN2atmosphereMgelementinAl-alloyscaninfiltrationprocess,buttheoxidefilmonthesurfaceofSiparticlesmaymakeagainstinfiltrationprocess.Anapproximateparabolacurveofinfiltrationdepthversusinfiltrationtimewasproved.ItwasobservedthatinfiltratingfrontofAluminum
8、alloysmeltliquidwascharacterizedbya.M.西北工业大学硕士学位论文planestate.
