冷卻速率對鎂基準(zhǔn)晶形成機(jī)制影響的研究.pdf

1、河北工業(yè)大學(xué)碩士學(xué)位論文冷卻速率對鎂基準(zhǔn)晶形成機(jī)制影響的研究姓名：蔚成全申請學(xué)位級別：碩士專業(yè)：材料加工工程指導(dǎo)教師：趙維民20100401冷卻速率對鎂基準(zhǔn)晶形成機(jī)制影響的研究iiEFFECTOFCOOLINGRATEONQUASICRYSTALFMATIONMECHANISMOFMGBASEDALLOYSABSTRACTTheeffectofcoolingrateonquasicrystalgrowthprocessfmationme

2、chanismofMgZnYbasedalloyshadbeenresearched.Theresearchcontentsmainlyincludethreeparts:effectofcoolingrateonquasicrystalmicrostructuresthermodynamicsdynamicsacteristics.AseriesofMgZnYalloyswithchemicalcompositionofMg72Zn2

3、6.5Y1.5werepreparedundervariouscoolingrateidentifiedbyusingopticalmicroscopy(OM)scanningelectronmicroscopy(SEM)XRaydiffraction(XRD)transmissionelectronmicroscopy(TEM).Studyofthecoolingconditioneffectonthemicrostructureof

4、MgZnYalloyswascarriedoutthetransfmofquasicrystalmphologywithcoolingrategrowthprocessfmationmechanismofquasicrystalwerestudied.TheresultsshowthatthehighercoolingratethelowerIphasetransitiontemperatureitwillbe.Themaximalfr

5、actionofIphasewasinthealloyunderthebestcoolingrate.AthermodynamicmodelthecalculationmethodofthechangeofGibbsfreeenergyduringtheprimarysolidificationofthequasicrystal(Mg30Zn60Y10)havebeenproposed.Thedrivingfceffmationofqu

6、asicrystallinephasegraduallydecreaseswithtemperaturedecreasesthecoolingrateincreases.Intherapidsolidificationprocessthefmationofquasicrystalwasinhibitedinthemelt.ByusingthethermodynamicmodelfthecalculationofthechangeofGi

7、bbsfreeenergyduringtheprimarysolidificationofthequasicrystalthenucleationenergiesnucleationratefthequasicrystalwarecalculated.Theresultsshowthatthequasicrystalnucleationenergiesdecreasesrapidlyfromtheliquidlineinthemeltt

8、henucleationratefthequasicrystalincreaseswithtemperaturedecreases.Inthelargercoolingratethenucleationenergiesfthequasicrystalarehigher.Howeverasthecoolingrateincreasesthenucleationrateincreasessharplyindicatingthattheapp