7075鋁合金熱變形時動態(tài)再結(jié)晶晶粒度演化模型

第23卷第10 2013年10 TheChineseJournalofNonferrous Oct1121111(1.2.成都飛機(jī)工業(yè)(集團(tuán))7075250~4500.1~1s?1的7075鋁合金熱變形時動態(tài)再結(jié)晶晶粒度演化模型。結(jié)果表明：根據(jù)唯象理論的指數(shù)模型，利用線性回歸方法確地預(yù)測7075鋁合金熱變形過程動態(tài)再結(jié)晶晶粒度。 Dynamicrecrystallizationgrainsizeevolutionmodelof7075aluminumalloyduringhotdeformationYANGDong1,CHENWen-lin1,WANGShao-yang2,MAYong1,ZHANGJin-ZHOURui1,ZHAOYa-pei1,WANGXin-(1.SchoolofMaterialsScienceandEngineering,HefeiUniversityofTechnology,Hefei230009,China?2.ChengduAircraftIndustrialCorporation,Chengdu610092,China)Abstract:Continuousdynamicrecrystallization(CDRX)of7075aluminumalloyoccursduringhotdeformation.Thethermalcompressionexperimentaboutthegroupofcylindricalspecimenwasdoneatthetemperatureof250?450℃andthestrainrateof0.1?1s?1.Themicrostructuregrainsizeof7075aluminumalloywasmeasuredbythemetallographicquantitativemethod,themicrostructuregrainsizeevolutionmodelof7075aluminumalloy.Theresultshowsthat,accordingtotheexponentialmodelofphenomenologicaltheoryandthelinearregressionmethod,themicrostructuregrainsizeevolutionmodelof7075aluminumalloyduringthethermoplasticdeformationcanbeworkedout.Andthen,bythefiniteelementsoftwarewiththeevolutionmodelcontinuousdynamicrecrystallizationgrainsizeof7075aluminumalloyduringhotdeformationwaspredicted.Theforecastingresultisveryclosetotheexperimentalone.Therefore,byfiniteelementsoftwarewiththeevolutionmodel,dynamicrecrystallizationgrainsizeof7075aluminumalloyduringthehotdeformationprocesscanbeaccuratelypredicted.Keywords:7075aluminumalloy?hotcompression?continuousdynamicrecrystallization?finiteelement?microstructuregrainsizeprediction

:7075核?長大”機(jī)制的非連續(xù)動態(tài)再結(jié)晶innuusdnmicrrtaliain,)度較高的情況下，可能出現(xiàn)部分非連續(xù)動態(tài)再結(jié)晶，7075鋁合金熱變形時主要發(fā)生連續(xù)動態(tài)再結(jié)晶(Cnnsnaicrrtallztin,)1?2]動態(tài)再結(jié)晶是金屬變形時位錯不斷向小角度晶界聚集，從而轉(zhuǎn)變?yōu)榇蠼嵌染Ы纾纬尚碌募?xì)小晶粒的過程。金屬晶粒度隨連續(xù)動態(tài)再結(jié)晶進(jìn)行而顯著減小，得到非常細(xì)小的晶粒組織，能夠顯著提高鋁合金材料的力學(xué)性能。因此，鋁及鋁合金的連續(xù)動態(tài)再結(jié)晶在工業(yè)生產(chǎn)中具有重要的意義，逐漸被研究學(xué)者所關(guān)注3?5。徐慶軍等[13]7075鋁合金熱變7075鋁合金高溫流變行為及神經(jīng)網(wǎng)絡(luò)本構(gòu)模7075707555元軟件來預(yù)報(bào)熱變形過程中各部分晶粒度的演化趨4605h的均勻1所示?？梢?，晶粒明顯沿?cái)D壓方向伸長，呈“紡

法測得其初始晶粒尺寸為40μm。7個試樣進(jìn)行不同溫度、應(yīng)變260、300、340℃，應(yīng)變速率分電阻直接加熱，加熱速度2℃/s，保溫時間3min。實(shí)驗(yàn)后將試樣迅速放入水中淬火以保留高溫組光面布金剛石粗拋?絨面布氧化鋁細(xì)拋?科勒腐蝕劑17075Table1Componentof7075aluminiumalloy(mass17075Fig.1 Initialmetallographicmicrostructuresof7075aluminumalloy:(a)Crosssection?(b)Longitudinalsection圖2壓縮實(shí)驗(yàn)后試樣中心區(qū)域的金相組Fig.2Metallographicmicrostructuresofcentralregionsofsamplesaftercompressionexperiments:(a)Sample1?(b)Sample(c)Sample3?(d)Sample4?(e)Sample(f)Sample6?(g)Sample2Table2Deformationparametersofcentralregionafter

可得圖3。根據(jù)兩數(shù)據(jù)點(diǎn)確定的直線，其斜率即為samplecompression area area 12345672根據(jù)GOURGET等[1]的研究，鋁合金動態(tài)再結(jié)晶

3lndCDRX—1/TFig.3lndCDRX—1/Tfittingstraight-

nmadnm

為塑性應(yīng)變；R為摩爾氣體常數(shù)；T為溫度；a為系數(shù)項(xiàng)；Q為激活能；k、n、m、p為指數(shù)項(xiàng)，由于本實(shí)驗(yàn)只針對初始晶粒度d0

dCDRXlndCDRXmln

dCDRX2、4、5觀測區(qū)的應(yīng)變速率和應(yīng)變相同，因此，其晶粒度僅僅正比于

44中三數(shù)據(jù)點(diǎn)確定的直線的斜率，m=?0.2BUFFA等[17]7075鋁合金RTdCDRXexpRT

數(shù)；Q為激活能；T為變形時的絕對溫度。對式(2)兩 4lndCDRXlnlndCDRX 7075鋁合金熱塑性變形組織晶粒度隨應(yīng)變值增dCDRX lndCDRXpln 2、6、7觀測區(qū)參數(shù)按式(7)處理，p5lndCDRXlnFig.5lndCDRX—lnfittingstraight-a1507075grainsize/um12345grainsize/um1234567

元模型如圖6所示。6Fig.6Finiteelement6所示的有限元模型對不同條件下(2所列的條件)7所示。試驗(yàn)后試樣中心處金相圖如表3所列。3Table3Comparisonofmeasuredgrainsizeandpredictedgrainsizeinobservationarea 40μm，將上述

3可以看出，測得的晶粒尺寸與有限元預(yù)報(bào)的7075鋁合金熱變形時動態(tài)再結(jié)晶晶粒度演化模型該有限元模型能夠準(zhǔn)確地預(yù)測7075鋁合金熱塑性變7Fig.7PredictedgrainsizebyFEMunderdifferent7075

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