循環(huán)熱處理對TiAl基合金組織與性能的影響.pdf

1、中南大學(xué)博士學(xué)位論文循環(huán)熱處理對TiAl基合金組織與性能的影響姓名：彭超群申請學(xué)位級別：博士專業(yè)：材料科學(xué)與工程指導(dǎo)教師：黃伯云2001.3.1●■中南大學(xué)博士學(xué)位論文AbstractThroughfeasibilityanalyses，simulatedtestsandinductionheattreatments，theeffectsofrapidheatingcyclicheattreatmentsonmicrostructure

2、sandmechanicalpropertiesofaTiAIbasedalloy(Ti一33AI3Crmassfraction，％)weresystematicallystudiedbymeansofopticalmicroscopyscanningelectronmicroscopytransmissionelectronmicroscopyX—raydiffractometryandcompressiontests，andthef

3、ollowingmainconclusionsaredrawn1)TheL16(45)orthogonalcyclicheattreatmenttestsshowthataccordingtOdifferentheattreatmentconditions(heatingratevh。25～10012／s，holdingtemperature01310～l34012，holdingtimet=2～5min，coolingratevc屹0

4、～16012／s，cyclingnumbern=l～7)，fourkindsofmicrostmcturescanbeobtained，ietypicallamellarstructure，mixedmicrostructureoffinelamellae，relativelycoarseiamellaeandmassivephase，finenearly1amellarmicrostructureandmassivemicrostru

5、ctureIntheselectedrangesoftheaboveparameters，whentheheatingrateislowerthan25℃／sandtheholdingtemperatureislouverthanl310“12orthecyclingnumberissmallerthan3，onlylamellarcoarseningandformationofsomenewnucleiOCCULThehardness

6、(HVs)Canbeincreasedbyrapidheatingcyclicheattreatment，andtheerrorrangeanalysisshowsthattheeffectsofheatingrate，holdingtemperature，holdingtime，coolingrateandcyclingnumberonhagdne$$。fromlargetosmall，areasfollows：vh；，，口，vcan

7、d打，amongwhichtheeffectofheatingrateisbyfarthemostevident、21111eoptimizedsinglefactortestofheatingrateshowsthatrapidlyheatedatarateof100～3200℃／s(0=1330℃，t=2rainv：50～80℃／s打=5)，thehardnessoftheTiAlbasedalloyCanbeincreasedby

8、30～70HV5comparedtothatoftheascastalloyandthemicrostructureCallberefinedtobeIesSthan50lam3)ThemicrostructureofthethermomechanicalllytreatedTiAIalloycallbefurtherrefinedbyrapidheatingcyclicheattreatmentForthetwostepmicrost