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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

Comparison of the effects of pre-activators on morphology and corrosion resistance of phosphate conversion coating on magnesium alloy

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Journal of Magnesium and Alloys 2022年第12期10卷 3485-3494页

作者： Tao Li Zhongjun Leng Shifang Wang Xitao Wang Reza Ghomashchi yuansheng yang Jixue Zhou Shandong Provincial Key Laboratory of High Strength Lightweight Metallic Materials Advanced Materials InstituteQilu University of Technology(Shandong Academy of Sciences)Jinan 250014China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Mechanical Engineering The University of AdelaideAdelaide SA 5005Australia

In this study, Mg–6.0Zn–3.0Sn–0.5Mn(ZTM630) magnesium alloy was pre-activated by colloidal Ti, oxalic acid, and phosphoric acid,and a phosphate conversion coating(PCC) was prepared on the alloy surface. The morphology and corrosion resistance of the prepared PCCs were investigated. Surface morphology studies showed that the phosphate crystals that formed the coating were the smallest for the sample pre-activated by phosphoric acid. The coating on the colloidal Ti and the phosphoric acid samples had the largest and the smallest thickness and surface roughness, respectively. The reason for the discrepancy was analyzed by comparing the surface morphologies of alloy samples immediately after the pre-activation treatment and various phosphating treatments. X-ray diffraction analysis revealed that all three PCCs contained the same compounds. The corrosion resistance time from the copper sulfate drop test and the electrochemical data from the potentiodynamic polarization curves showed that the coating pre-activated by phosphoric acid had the best corrosion resistance. Finally, the 1500 h neutral salt spray corrosion test confirmed that the phosphating treated magnesium alloy, which was pre-activated by phosphoric acid,exhibited excellent corrosion resistance and behavior.

关键词： Phosphate conversion coating Surface pre-activator Magnesium alloy Morphology Corrosion

Achieving high strength-ductility synergy in a Mg_(97)Y_(1)Zn_(1)Ho_(1) alloy via a nano-spaced long-period stacking-ordered phase

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Journal of Magnesium and Alloys 2023年第4期11卷 1321-1331页

作者： Mingyu Fan Ye Cui yang Zhang Xinghao Wei Xue Cao Peter K.Liaw yuansheng yang Zhongwu Zhang Key Laboratory of Superlight Materials and Surface Technology Ministry of EducationCollege of Materials Science and Chemical EngineeringHarbin Engineering UniversityHarbin 150001PR China College of Computer Science and Technology Harbin Engineering UniversityHarbin 150001PR China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996-2100USA Institute of Metal Research Chinese Academy of SciencesShenyang 110016PR China

Achieving high strength in Mg alloys is usually accompanied by ductility loss.Here,a novel Mg97Y1Zn1Ho1 at.%alloy with a yield strength of 403 MPa and an elongation of 10%is developed.The strength-ductility synergy is obtained by a comprehensive strategy,including a lamella bimodal microstructure design and the introduction of nano-spaced solute-segregated 14H long-period stacking-ordered phase(14H LPSO phase)through rare-earth Ho alloying.The lamella bimodal microstructure consists of elongated un-recrystallized(un-DRXed)coarse grains and fine dynamically-recrystallized grains(DRXed regions).The nano-spaced solute-segregated 14H LPSO phase is distributed in DRXed regions.The outstanding yield strength is mainly contributed by grain-boundary strengthening,18R LPSO strengthening,and fiberlike reinforcement strengthening from the nano-spaced 14H LPSO phase.The high elongation is due primarily to the combined effects of the bimodal and lamellar microstructures through enhancing the work-hardening capability.

关键词： Mg wrought alloy Mechanical properties Long-period stacking-ordered(LPSO)phase Age-strengthening behavior Strengthening 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

Effect of crystal orientation on corrosion behavior of directionally solidified Mg-4 wt% Zn alloy

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Journal of Materials Science & Technology 2018年第7期34卷 1229-1235页

作者： Hongmin Jia Xiaohui Feng yuansheng yang Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China University of Chinese Academy of Sciences Beijing 100039 China Shandong Key Laboratory for High Strength Lightweight Metallic Materials Jinan 250014 China

Microstructure and crystallographic orientation of directionally solidified Mg-4 wt% Zn alloy were characterized by X-ray computed tomography （XCT） and electron backscatter diffraction （EBSD） in this study. Results reveal that Mg-4 wt% Zn alloy with dendritic microstructure exhibits typical { 0002} basal texture along growth direction. Based on this, the effect of grain orientation on corrosion behavior of directionally solidified Mg-4 wt% Zn alloy in 0.9 wt% NaCl solution was investigated. Result shows that {0002} oriented planes have better corrosion resistance than {1120} and {1010 } ones, which is attributed to a synergistic effect of surface energy, atomic packing density and the stability of oxidation film,2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology,

关键词： Mg-4 wt% Zn alloy Directional solidification Crystal orientation Corrosion resistance

Improving mechanical properties of age-hardenable Mg–6Zn–4Al–1Sn alloy processed by double-aging treatment

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Journal of Materials Science & Technology 2017年第11期33卷 1249-1254页

作者： Shaozhen Zhu Tianjiao Luo yuansheng yang Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering Northeastern University Shenyang 110819 China Shandong Key Laboratory for High Strength Lightweight Metallic Materials Jinan 250014 China

Microstructure and mechanical properties of a new high-strength Mg–6 Zn–4 Al–1 Sn alloy were investigated. Microstructure of the as-cast Mg alloy exhibited partially divorced characteristics. The dendritic structure of the Mg–6 Zn–4 Al alloy was significantly refined with the addition of 1%（in weight） Sn, but Mg2 Sn phases were not formed. In addition, an icosahedral quasi-crystal phase was formed in the as-cast Mg–6 Zn–4 Al–1 Sn alloy. It was found that after the double-aging treatment through two different heat treatments on the Mg–6 Zn–4 Al–1 Sn alloy, the precipitates were finer and far more densely dispersed in the matrix compared with single-aged counterpart, resulting in a significant improvement in tensile strength with yield strength, ultimate tensile strength and elongation of 175 MPa, 335 MPa and 11%,respectively.

关键词： Magnesium alloy Mg–Zn–Al–Sn Double-aging treatment Mechanical properties

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