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Controlling dynamic recrystallization via modified LPSO phase morphology and distribution in Mg-Gd-Y-Zn-Zr alloy

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Journal of Magnesium and Alloys 2023年第11期11卷 4218-4234页

作者： Ce Zheng Shuaifeng Chen Ming Cheng Shihong Zhang yingju li Yuansheng Yang Shi-changxu Innovation Center for Advanced Material Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

Featured initial microstructures of Mg-11Gd-4Y-2Zn-0.5Zr alloy(wt%) were obtained by adjusting temperatures of solid solution and cooling methods, including island intergranular 18R and 14H LPSO phases with low-density stacking faults, differentially spaced lamellar intragranular 14H-LPSO phases, and network intergranular 18R-LPSO phases with high-density intragranular stacking faults. Effects of these featured LPSO phases and stacking faults on dynamic recrystallization(DRX) behavior were investigated via hot compression. Promoted DRX behavior via particle stimulated nucleation(PSN) is introduced by coexisting intergranular island 18R and 14H LPSO phases and intragranular wide spacing lamellar 14H-LPSO phases, contributing the highest DRX fraction of 42.6%. Conversely, it is found that DRX behavior with network intergranular 18R-LPSO phases and dense intragranular stacking fault is considerably inhibited with the lowest fraction of 22.8%. That is, the restricted DRX due to dislocations pinning by stacking faults overwhelms the enhanced DRX behavior via PSN of island intergranular 18R and 14H LPSO phases. Specially, compared with dense intragranular lamellar 14H-LPSO phases, high-density stacking faults exert a larger inhibition effect on DRX behavior.

关键词： Mg-Gd-Y-Zn-Zr Dynamic recrystallization LPSO phases Particle stimulated nucleation Stacking fault

The corrosion characteristics and mechanism of directionally solidified Mg-3Zn-xCa alloys

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Journal of Magnesium and Alloys 2023年第10期11卷 3673-3687页

作者： Yi Zhang Xiaohui Feng Qiuyan Huang yingju li Xuehui Hao Changzheng Wang Yuansheng Yang Institute of Metal Research Chinese Academy of Scienceswenhua road 72Shenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China School of Materials Science and Engineering Liaocheng UniversityLiaocheng 252000China

An investigation into the corrosion characteristics and mechanism of directionally solidified(DSed) Mg-3Zn-xCa(x = 0, 0.2, 0.5,0.8 wt.%) alloys in 0.9 wt.% Na Cl solution is presented. The DSed microstructure consists of columnar dendrites and eutectics distributed in the interdendritic region. The primary dendritic arm spacing(PDAS) and the volume fraction(fv) of the secondary phases are under the significant impact of the content of Ca. The corrosion rates evaluated using electrochemical measurements and immersion tests are accelerated monotonously with the increase of Ca content in DSed alloys. The corrosion resistance of the DSed alloys is significantly affected by the corrosion products film(CPF) and the secondary phases. The corrosion products of DSed Mg-3Zn alloy contain Mg(OH)_(2) and ZnO. The existence of ZnO greatly enhances the corrosion resistance of DSed Mg-3Zn alloy. As for the DSed alloys containing Ca content, a relatively protective CPF without deep pits can form on the surface of DSed Mg-3Zn-0.2Ca specimen during the corrosion. The f_(v)of the secondary phases dominates the corrosion rate of the DSed Mg-Zn-Ca alloys. The corrosion of DSed Mg-3Zn-xCa alloys initiates as a result of microgalvanic coupling between the cathodes of secondary phases and α-Mg matrix anode. Then, the corrosion gradually extends longitudinally with the breakdown of CPF.

关键词： Mg-Zn-Ca alloy Directional solidification Electrochemical characterization Corrosion mechanism

Simulation of the Influence of Pulsed Magnetic Field on the Superalloy Melt with the Solid-liquid Interface in Directional Solidification

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Acta Metallurgica Sinica(English Letters) 2020年第10期33卷 1442-1454页

作者： Kuiliang Zhang yingju li Yuansheng Yang Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

The effect of the pulsed magnetic field on the grain refinement of superalloy K4169 has been studied in directional solidification.In the presence of the solid-liquid interface condition,the distributions of the electromagnetic force,flow field,temperature field,and Joule heat in front of the solid-liquid interface in directional solidification with the pulsed magnetic field are simulated.The calculation results show that the largest electromagnetic force in the melt appears near the solid-liquid interface,and the electromagnetic force is distributed in a gradient.There are intensive electromagnetic vibrations in front of the solid-liquid interface.The forced melt convection is mainly concentrated in front of the solid-liquid interface,accompanied by a larger flow velocity.The simulation results indicate that the grain refinement is attributed to that the electromagnetic vibration and forced convection increase the nucleation rate and the probability of dendrite fragments survival,for making dendrite easily fragmented,homogenizing the melt temperature,and increasing the undercooling in front of the solid-liquid interface.

关键词： Pulsed magnetic field Solid–liquid interface Simulation Electromagnetic force Melt convection Superalloy

Influence of the low voltage pulsed magnetic field on the columnar-to-equiaxed transition during directional solidification of superalloy K4169

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Journal of Materials Science & Technology 2020年第13期47卷 9-17页

作者： Kuiliang Zhang yingju li Yuansheng Yang Institute of Metal Research Chinese Academy of SciencesShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei230026China

The low voltage pulsed magnetic field(LVPMF)disrupts the columnar dendrite growth,and the columnarto-equiaxed transition(CET)occurs during the directional solidification of superalloy K4169.Within the pulse voltage ranging from 100Vto 200 V,a transition from columnar to equiaxed grain was observed,and the grain size decreased as the pulse voltage rised.As the pulse frequency increased,the CET occurred,and the grains were refined.However,the grains became coarse,and the solidification structure was columnar crystal again when frequency increased to 10 Hz.The LVPMF had an optimal frequency to promote CET.The LVPMF on the CET was affected by the withdrawal speed and increasing the withdrawal speed enhances the CET.The distribution of electromagnetic force and flow field in the melt under the LVPMF were modeled and simulated to reveal the CET mechanism.It is considered that the CET should be attributed to the coupling effects of magnetic vibration and melt convection induced by the LVPMF.

关键词： CET Low voltage pulsed magnetic field Simulation Directional solidification Superalloy

Effects of Pulsed Magnetic Field on Microsegregation of Solute Elements in a Ni-Based Single Crystal Superalloy

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Journal of Materials Science & Technology 2017年第1期33卷 105-110页

作者： yingju li Yuefei Teng Xiaohui Feng Yuansheng Yang Superalloy Division Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

The effects of a pulsed magnetic field （PMF） on the microsegregation of solute elements during directional solidification of a Ni-based single crystal superalloy were experimentally investigated, and the results show that the PMF significantly affects the microsegregation of Al, Ti, Co, Mo and W elements in the alloy. However, the distribution behavior differs for both positive and negative segregation elements. With the PMF, the microsegregation of negative segregation elements, Co and W, was restrained effectively, while that of positive segregation elements, A1, Ti and Mo, was aggravated. A segregation model was estab- lished to reveal the distribution mechanism of the elements with PME It is considered that, under the action of PME the jumping of solute atoms from the liquid phase to solid phase is hindered, but the jumping of solute atoms from the solid phase into liquid phase is promoted during solidification. As a result, the effective distribution coefficient of the solute atoms is reduced, which leads to the reduction of microsegregation of negative segregation elements and aggravation of microsegregation of positive segregation elements.

关键词： Pulsed magnetic field Segregation Superalloy Distribution coefficient

Fluidity, Microstructure, and Tensile Properties of Sub-rapidly Solidified Mg-6Al-4Zn-xSn(x=0,0.6,1.2,1.8) Alloy

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Acta Metallurgica Sinica(English Letters) 2021年第9期34卷 1265-1276页

作者： Jie Cui Tianjiao Luo yingju li Xiaohui Feng Qiuyan Huang Yuansheng Yang School of Materials Science and Engineering Northeastern UniversityShenyang 110819China Institute of Metal Research Chinese Academy of ScienceShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

In this paper, the infl uence of the Sn element on the melt viscosity, grain size, shrinkage, and tensile properties of the subrapidly solidified Mg-6Al-4Zn alloy was studied. The results showed that the melt viscosity of the Mg-6Al-4Zn alloy was greatly decreased because of the addition of Sn. As the content of Sn increased from 0 to 1.8 wt.%, the grain size of the alloy was refined, and the dendrite microstructure was changed to rose-shaped ones simultaneously. The decreased melt viscosity and refined microstructure were conductive to the feeding of melt, which contributed to the reduction in volume fraction of shrinkage. The volume fraction of shrinkage of the Mg-6Al-4Zn-1.2 Sn alloy was reduced by 30.8%, compared with that of the alloy without Sn addition. Tensile properties of the Mg-6Al-4Zn-x Sn alloys were increased firstly and then decreased with the augmented Sn content. The yield strength, ultimate tensile strength, and elongation of the alloy containing 1.2 wt.% Sn were 21.4%, 39.5%, and 259.0% higher than those of the alloy without Sn addition, respectively. The addition of Sn was considered to reduce the shrinkage of the sub-rapidly solidified Mg-6Al-4Zn magnesium alloy and thus improved its tensile properties. To identify the mechanism, the effect of Sn on the volume fraction of shrinkage was discussed from three aspects of melt viscosity, grain refinement, and volume fraction of eutectic phases.

关键词： Magnesium alloy Melt viscosity Grain size Shrinkage Tensile properties

Effect of Pulsed Magnetic Field on the Residual Stress of Rolled Magnium Alloy AZ31 Sheet

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Acta Metallurgica Sinica(English Letters) 2021年第1期34卷 45-53页

作者： Meng Yan Cong Wang Tianjiao Luo yingju li Xiaohui Feng Qiuyan Huang Yuansheng Yang Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

A novel method of pulsed magnetic field(PMF)treatment was developed to eliminate the residual stress of rolled magnesium alloy AZ31 sheet in this study.The eff ect of PMF on residual stress of rolled AZ31 sheet was investigated and its mechanism was analyzed.The experimental results revealed that the pulse frequency had a significant impact on residual stress.After 10.0 Hz PMF treatment,the average and maximum reduction rates of residual stress along the rolled direction were 26.6%and 30.3%,respectively.It was found that the dislocation density and parallel dislocation in grains of the rolled sheet increased after it was treated by the pulsed magnetic field.The simulation results showed that the Lorentz force generated by the pulsed magnetic field can lead to basal slip,thereby resulting in local plastic deformation.Besides,the Joule heat produced during the PMF treatment was conducive to the elimination of residual stress.

关键词： Wrought magnesium alloy Residual stress Pulsed magnetic field Rolled AZ31 sheet

Age hardening responses of as-extruded Mg-2.5Sn-1.5Ca alloys with a wide range of Al concentration

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Journal of Materials Science & Technology 2020年第3期38卷 39-46页

作者： Qiuyan Huang Yang liu Aiyue Zhang Haoxin Jiang Hucheng Pan Xiaohui Feng Changlin Yang Tianjiao Luo yingju li Yuansheng Yang Institute of Metal Research Chinese Academy of SciencesShenyang110016China Key Laboratory for Anisotropy and Texture of Materials(MOE) School of Materials Science and EngineeringNortheastern UniversityShenyang110819China Research Center for Metallic Wires Northeastern UniversityShenyang110819China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China

This article aims to explore the age hardening responses of both as-extruded and as-aged Mg-2.5 Sn-1.5 Ca-x Al alloys(x=2.0,4.0 and 9.0 wt%,termed TXA322,TXA324 and TXA329,respectively)through microstructural and mechanical characterization.Results indicate that grain size of as-extruded TXA322,TXA324 and TXA329 alloys were^16μm,~10μm and^12μm,respectively.A number ofanddislocations were observed in all the as-extruded samples.Guinier–Preston(GP)zones were evidently identified in TXA322 alloy,while only a small number of Mg17 Al12 phases existed in both TXA324 and TXA329 alloys.An aging treatment facilitated the precipitation of a high number density of GP zones within the matrix of TXA322 alloy.In contrast,no obvious nano-precipitates were in as-aged TXA324 alloy.Numerous nano-Mg17 Al12 phases were formed through a following aging treatment in TXA329 alloy.In terms of mechanical properties,it is apparent that an increment in ultimate tensile strength of^46 MPa and^40 MPa was yielded in peak-aged TXA322 and TXA329 alloys,while no obvious variations in UTS were present in peak-aged TXA324 alloy,in comparison with the as-extruded counterparts.

关键词： Magnesium alloys Age hardening Precipitations Dislocations Mechanical properties

Mg-8Zn-4Al-0.5Cu-0.5Mn-xli高模量铸造镁合金的组织和性能

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材料研究学报 2024年第3期38卷 187-196页

作者：刘晨野罗天骄李应举冯小辉黄秋燕郑策朱成杨院生中国科学院金属研究所沈阳110016 中国科学技术大学材料科学与工程学院沈阳110016

设计和制备Mg-8Zn-4Al-0.5Cu-0.5Mn-x li(x=0,3,5,7)(%,质量分数)系列高比模量的镁合金,研究了它的组织和性能。li含量为3.14%和5.37%的两种镁合金,其基体为单相α-Mg,在晶界析出骨骼状Mg_(32)(Al,Zn)49相,在晶粒内有颗粒状Mg_(5)Al_(2)Zn_(2)相和Al_(2)Mn相;li含量为7.57%的合金,其基体主要为双相组织α-Mg+β-li。添加li元素后在晶界附近生成的共晶组织由α-Mg相和层片状Alli相组成,并随着li含量的提高层片状Alli相的含量随之提高。随着li含量的提高,合金的屈服强度呈逐渐提高的趋势,而抗拉强度基本上不变,合金的弹性模量呈现先提高后降低的趋势。铸态合金ZA84-5li的弹性模量可达51.89 GPa,比纯Mg的弹性模量高7 GPa,但是其力学性能基本不变,屈服强度为141 MPa,抗拉强度为189 MPa,密度为1.71 g/cm^(3)。

关键词：金属材料镁合金第二相强化显微组织弹性模量