双重梯度保温下多元稀土对A356铝合金初生相细化的影响
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摘要
在双重梯度保温工艺下,研究Gd-Y-Nd-Ce四元稀土复合细化剂对半固态A356铝合金初生相产生多重细化效果。结果表明:共晶产物α(Al)的相对量为99%以上,是细化效率最高的有效形核基底,因此在A356铝合金液相线附近保证其较高的存活率对初生相的细化至关重要;另一共晶产物RExAly不足1%,其在不同裸露晶面上存在不同的错配度(形核效率)。由于梯度保温对多元共晶产物存活率的调控,使得其在种类、尺寸、数量、错配度等方面展现出多样化。A356-RE铝合金在650℃浇注,并按照645℃/30 s,635℃/40 s,625℃/50 s,615℃/60 s进行梯度保温,水淬后,在优化方案下(0.5%Gd+0.4%Y+0.2%Nd+0.2%Ce,质量分数),获得的初生相平均等积圆直径为85.118μm,形状因子为0.786,细化效果最好。
The multiple refining effect of Gd-Y-Nd-Ce four rare earth composite refiner on the primary phase of semi-solid A356 alloy was studied under dual gradient isothermal holding technique. The results indicate that the eutectic product α(Al) of relative amount is more than 99%, which is the effective nucleation site. Thus ensuring its high survival rate in the near liquidus of A356 alloy was very important for the refinement of primary phase. The other eutectic product RExAly is less than 1%, which has different degree of mismatching(nucleation efficiency) in different exposed grain surfaces. Due to the regulation of multiple eutectic products' survival efficiency by gradient thermal insulation, which makes them show the diversity in variety, size, quantity, mismatch degree and so on. In this test, A356-RE alloy is poured at 650 ℃, then gradient isothermal holding is carried according to 645 ℃/30 s, 635 ℃/40 s, 625 ℃/50 s, 615 ℃/60 s.After water quenching, under the optimal composition(0.5%Gd+0.4%Y+0.2%Nd+0.2%Ce, mass fraction), the primary phase of A356 alloy with equal-area circle diameter of 85.118μm and shape factor 0.786 is obtained, in which the refining effect is the best.
The multiple refining effect of Gd-Y-Nd-Ce four rare earth composite refiner on the primary phase of semi-solid A356 alloy was studied under dual gradient isothermal holding technique. The results indicate that the eutectic product α(Al) of relative amount is more than 99%, which is the effective nucleation site. Thus ensuring its high survival rate in the near liquidus of A356 alloy was very important for the refinement of primary phase. The other eutectic product RExAly is less than 1%, which has different degree of mismatching(nucleation efficiency) in different exposed grain surfaces. Due to the regulation of multiple eutectic products' survival efficiency by gradient thermal insulation, which makes them show the diversity in variety, size, quantity, mismatch degree and so on. In this test, A356-RE alloy is poured at 650 ℃, then gradient isothermal holding is carried according to 645 ℃/30 s, 635 ℃/40 s, 625 ℃/50 s, 615 ℃/60 s.After water quenching, under the optimal composition(0.5%Gd+0.4%Y+0.2%Nd+0.2%Ce, mass fraction), the primary phase of A356 alloy with equal-area circle diameter of 85.118μm and shape factor 0.786 is obtained, in which the refining effect is the best.
引文
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[13]WANG J, NIE J J, WANG R, XU Y D, ZHU X R, LING G P.EffectofYonagehardeningresponseandmechanical properties of Mg-x Y-1.5LPC-0.4Zr alloys[J]. Transactions of NonferrousMetalsSocietyofChina,2012,22(7):1549-1555.
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[15]刘政,谌庆春,郭颂,刘俊义,胡钱钱. A356-RE合金中稀土铝化物/初生α相界面二维错配度的计算及验证[J].稀有金属材料与工程, 2015, 44(4):859-865.LIU Zheng, CHEN Qing-chun, GUO Song, LIU Jun-yi, HU Qian-qian.Calculationofplanardisregistriesbetween compounds of rare earth-Al and primaryαphase in A356-RE alloyanditsverification[J].RareMetalMaterialsand Engineering, 2015, 44(4):859-865.
[16]BARRIRERO J, ENGSTLER M, GHAFOOR N, JONGE N D,ODENM,MUCKLICHF.Comparisonofsegregations formed in unmodified and Sr-modified Al-Si alloys studied byatomprobetomographyandtransmissionelectron microscopy[J].JournalofAlloysandCompounds,2014,611(12):410-421.
[17]EASTON M A, STJOHN D. An analysis of the relationship betweengrainsize,solutecontent,andthepotencyand numberdensityofnucleantparticles[J].Metallurgicaland Materials Transactions A, 2005, 36(7):1911-1920.
[18]JIANGN,CHENL,MENGLG,FANGCF,HAOH,ZHANG X G. Effect of neodymium, gadolinium addition on microstructureandmechanicalpropertiesofAZ80magnesiumalloy[J].JournalofRareEarths,2016,34(6):632-637.
[19]WANGL,YANGL,ZHANGD,XIAMX,WANGY,CHENB,LIJG.NucleationinterfaceofAl-Sballoyson single crystal Al2O3 substrate[J]. Transactions of Nonferrous Metals Society of China, 2017, 27(9):2104-2111.
[20]SPEAROT D E, JACOB K I, MCDOWELL D L. Nucleation ofdislocationsfrom
[001]bicrystalinterfacesin aluminum[J]. Acta Materialia, 2005, 53(13):3579-3589.
[2]VIJEESH V, PRABHU K N. The effect of chilling and Ce addition on the microstructure and mechanical properties of Al-23Sialloy[J].JournalofMaterialsEngineering&Performance, 2017, 26(1):343-349.
[3]LATORREAD,PEREZ-BUSTAMANTER,CAMARILLO-CISNEROSJ,GOMEZ-ESPARZACD,MEDRANO-PRIETOHM,MARTINEZ-SANCHEZR.Mechanical properties of the A356 aluminum alloy modified with La/Ce[J]. Journal of Rare Earths, 2013, 31(8):811-816.
[4]HOSSEINIFARM,MALAKHOVDV.Thesequenceof intermetallicsformationduringthesolidificationofan Al-Mg-Si alloy containing La[J]. Metallurgical and Materials Transactions A, 2011, 42(3):825-833.
[5]MAOF,YANGY, XUANZJ,CAOZQ,WANGTM.Effect of Eu addition on the microstructures and mechanical properties of A356 aluminum alloys[J]. Journal of Alloys and Compounds, 2015, 650:896-906.
[6]MOUSAVI G S, EMAMY M, RASSIZADEHGHANI J. The effectofmischmetalandheattreatmentonthe microstructure and tensile properties of A357 Al-Si casting alloy[J]. Materials Science and Engineering A, 2012, 556(11):573-581.
[7]LIUZ,LIUXM,HUYM.Microstructurerefinementby Y2O3insemisolidA356alloy[J].AdvancedMaterials Research, 2011, 311/313:666-669.
[8]MURTYBS,KORISA,CHAKRABORTYM.Grain refinementofaluminiumanditsalloysbyheterogeneous nucleation and alloying[J]. Internatiional Materials Reviews,2002, 47(1):3-29.
[9]NOGITAK,MCDONALDSD,DAHLEAK.Eutectic modificationofAl-Sialloyswithrareearthmetals[J].Materials Transactions, 2004, 45(2):323-326.
[10]LIU Z, HU Y M. Effect of yttrium on the microstructure of a semi-solidA356Alalloy[J].RareMetals,2008,27(5):536-540.
[11]LIU Z, HUANG M Y, CAO K, XU H B. Effect of eutectic reaction induced by La on microstructure in semisolid A356alloy[J].AdvancedMaterialsResearch,2012,424/425:70-80.
[12]LIU Z, LUO H L, CHEN Q C. The refinement mechanism of La-Ce binary alloy on primaryαphase in A356 alloy under electromagneticstirring[J].SolidStatePhenomena,2015,217/218:340-346.
[13]WANG J, NIE J J, WANG R, XU Y D, ZHU X R, LING G P.EffectofYonagehardeningresponseandmechanical properties of Mg-x Y-1.5LPC-0.4Zr alloys[J]. Transactions of NonferrousMetalsSocietyofChina,2012,22(7):1549-1555.
[14]冯艳,李晓庚,王日初,彭超群.热处理过程中Mg-8Gd-3Y-1Nd-0.5Zr合金的组织演变及性能[J].中国有色金属学报, 2017, 27(9):1794-1802.FENG Yan, LI Xiao-geng, WANG Ri-chu, PENG Chao-qun.MicrostructureevolutionandperformanceofMg-8Gd-3Y-1Nd-0.5Zralloyduringheattreatment[J].TheChinese Journal of Nonferrous Metals, 2017, 27(9):1794-1802.
[15]刘政,谌庆春,郭颂,刘俊义,胡钱钱. A356-RE合金中稀土铝化物/初生α相界面二维错配度的计算及验证[J].稀有金属材料与工程, 2015, 44(4):859-865.LIU Zheng, CHEN Qing-chun, GUO Song, LIU Jun-yi, HU Qian-qian.Calculationofplanardisregistriesbetween compounds of rare earth-Al and primaryαphase in A356-RE alloyanditsverification[J].RareMetalMaterialsand Engineering, 2015, 44(4):859-865.
[16]BARRIRERO J, ENGSTLER M, GHAFOOR N, JONGE N D,ODENM,MUCKLICHF.Comparisonofsegregations formed in unmodified and Sr-modified Al-Si alloys studied byatomprobetomographyandtransmissionelectron microscopy[J].JournalofAlloysandCompounds,2014,611(12):410-421.
[17]EASTON M A, STJOHN D. An analysis of the relationship betweengrainsize,solutecontent,andthepotencyand numberdensityofnucleantparticles[J].Metallurgicaland Materials Transactions A, 2005, 36(7):1911-1920.
[18]JIANGN,CHENL,MENGLG,FANGCF,HAOH,ZHANG X G. Effect of neodymium, gadolinium addition on microstructureandmechanicalpropertiesofAZ80magnesiumalloy[J].JournalofRareEarths,2016,34(6):632-637.
[19]WANGL,YANGL,ZHANGD,XIAMX,WANGY,CHENB,LIJG.NucleationinterfaceofAl-Sballoyson single crystal Al2O3 substrate[J]. Transactions of Nonferrous Metals Society of China, 2017, 27(9):2104-2111.
[20]SPEAROT D E, JACOB K I, MCDOWELL D L. Nucleation ofdislocationsfrom
[001]bicrystalinterfacesin aluminum[J]. Acta Materialia, 2005, 53(13):3579-3589.