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Microstructures and mechanical properties of homogenization and isothermal aging Mg–Gd–Er–Zn–Zr alloy

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Rare Metals 2016年第6期35卷 443-449页

作者： Kai Wen Wen-bo Du Ke liu Zhao-Hui Wang shu-bo li College of Materials Science and Engineering Beijing University of Technology

The effects of homogenization and isothermal aging treatment on the mechanical properties of Mg-12Gd- 2Er-1Zn-0.6Zr （wt%） alloy were investigated. The precipitated long-period stacking order （LPSO） structure and the aging precipitation sequence of the conditioned alloys were observed and analyzed, respectively. The results indicate that the 14H-LPSO structure occurs after the homogenization treatment and the 131 phase forms after the isothermal aging process. These two independent processes could be controlled by the precipitation temperature range. The significant increase in the elongation of the as-cast alloy after homogenization treatment is attributed to the disappearance of the coarse primary Mgs（Gd, Er, Zn） phase and the presence of the 14H-LPSO structure. The precipitation sequence of the investigated alloy is α-Mg（SSS）/β″（D019）/β′（cbco）/β. Furthermore, the yield tensile strength （YTS） and ultimate tensile strength （UTS） values of the isothermal aging alloy have a great improvement, which could be attributed to the high density of the precipitated β′ phase.

关键词： Magnesium alloys Isothermal aging Mechanical properties Mg-Gd-Er-Zn(Zr) Microstructures

Microstructure and mechanical properties of AZ31 magnesium alloy reinforced by I-phase

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Rare Metals 2019年第8期38卷 733-738页

作者： Hai-Rong Wu Wen-bo Du shu-bo li Ke liu Zhao-Hui Wang School of Materials Science and Engineering Beijing University of Technology

The particles of Mg-Zn-Gd icosahedral quasicrystal master alloy were added into the AZ31 alloy by the repeated plastic working(RPW)process in order to improve the mechanical properties of the AZ31 alloy at room *** microstructure and tensile properties of composites were investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and tensile testing machine at room *** results suggest that the RPW process can effectively refine the matrix and make the I-phase particles distribute *** ultimate tensile strength and the yield strength of the composites reach their maximum values of 362.3 and 330.5 MPa,respectively,when the amount of I-phase particles added is10 %.Meanwhile,the elongation of the composites decreases sharply.

关键词： I-phase Reinforced composite Repeated plastic working Mechanical property

Microstructural control and hardening response of Mg–6Zn–0.5Er–0.5Ca alloy

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Rare Metals 2016年第7期35卷 526-531页

作者： Xiao-Bing Zheng Ke liu Zhao-Hui Wang shu-bo li Wen-bo Du School of Material Science and Engineering Beijing University of Technology

The effects of heat treatment on microstructures and hardening response of Mg-6Zn4）.5Er4）.5Ca （wt%） alloy were investigated by optical microscope （OM）, scanning elec- tron microscope （SEM）, and transmission electron microscope （TEM） in this paper. The results show that the Mg（Zn4）.5Er- 0.5Ca alloy contains Mg3Zn6Erx quasicrystalline phase （I- phase） and Ca2Mg6Zn3 phase under as-cast condition. Most of the Ca2Mg6Zn3 phases and I-phases dissolve into matrix during heat treatment at 475 ℃ for 5 h. After the as-solution alloy was aged at 175 ℃ for 36 h, a large amount of MgZn2 precipitate with several nanometers precipitate. It is suggested that the trace addition of Ca results in refining the size of the precipitate, and the presence of the nanoscale MgZn2 phase is the main factor to improve the peak-aged hardness greatly to 87 HV, which in- creases about 40 % compared with that of as-cast alloy.

关键词： Mg-6Zn-0.5Er-0.5Ca alloy Heat treatment Aging hardening

Microstructure and electrochemical properties of La0.8-xMMxMg0.2Ni3.1Co0.3Al0.1(x=0,0.1,0.2,0.3)alloys

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Rare Metals 2017年第8期36卷 645-650页

作者： Na Zhou Wen-bo Du Pei-Long Zhang Yong-Guo Zhu Zhao-Hui Wang Ke liu shu-bo li College of Materials Science and Engineering Beijing University of TechnologyBeijing 100124China Whole Win Materials Science and Technology Co. LtdBeijing 100083China

The present study aims to improve electrochemical properties of the La-Mg-Ni-based hydrogen storage alloys through partial substitution for La by mischmetal（MM）.The La_（0.8-x）MM_xMg_（0.2）Ni_（3.1）Co_（0.3）Al_（0.1）（x=0,0.1,0.2,0.3）alloys were prepared by inductive melting,and their phase structures and electrochemical properties were studied by X-ray diffraction（XRD）,scanning electron microscope（SEM）,energy-dispersive X-ray spectrometry（EDX）and electrochemical *** show that the alloys mainly consist of La_2Ni_7-type phase,La_5Ni_（19）-type phase,LaNi_5-type phase and LaNi_3-type *** addition of MM does not change the phase compositions,while it leads to more uniform phase distribution and obviously promotes the formation of La_2Ni_7-type phase which possesses favorable electrochemical *** studies indicate that the substitution for La by MM could effectively improve the high rate dischargeability（HRD）of the alloy electrode,and the optimal value of HRD_（1500）（HRD at 1500 mA·g^（-1））increases from 40.63%（x=0）to 60.55%（x=0.3）.Although the activation properties of the alloy electrodes keep almost unchanged,both the maximum discharge capacity（C_（max））and the cycling stability are significantly improved by MM addition.

关键词： Hydrogen storage alloy Microstructure Discharge capacity High rate dischargeability Cyclingstability

Microstructure,mechanical properties and stretch formability of as-rolled Mg alloys with Zn and Er additions

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Rare Metals 2021年第8期40卷 2179-2187页

作者： Ke liu Jing-Tao liang Wen-bo Du shu-bo li Zhao-Hui Wang Zi-Jian Yu Jin-Xue liu College of Materials Science and Engineering Beijing University of TechnologyBeijing100124China Zhengzhou light Metal Research Institute Zhengzhou450041China

The magnesium alloy has a unique advantage in 3C fields due to its high specific strength and excellent electromagnetic shielding ***,it is difficult to deform homogeneously because of hexagonal close-packed *** the present work,the microstructure,mechanical properties and stretch formability of magnesium alloy sheets with different alloying elements were *** was indicated that a trace addition of Zn or/and Er made a key role in modifying texture,activating shear bands formation and precipitating nanoscale second phases,respectively,which resulted in an obvious improvement in both stretch formability and mechanical *** results suggested that the Mg-0.5 Zn-0.5 Er alloy sheet exhibited higher tensile strength along the rolling direction,i.e.,yield strength of 180 MPa and ultimate tensile strength of 201 MPa,accompanying with superior Erichsen value of 7.0 mm at room *** good performances of the sheet were ascribed to weakening basal texture intensity,formation of shear bands and precipitation of nanoscale W-phase(Mg_(3)Zn_(3)Er_(2)).

关键词： Mg-Zn-Er alloy Hot rolling Texture Shear band Stretch formability

Obtaining Ultra-High Strength and Ductility in a Mg–Gd–Er–Zn–Zr Alloy via Extrusion,Pre-deformation and Two-Stage Aging

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Acta Metallurgica Sinica(English Letters) 2021年第1期34卷 39-44页

作者： lin-Yue Jia Wen-bo Du Jin-Long Fu Zhao-Hui Wang Ke liu shu-bo li Xian Du College of Materials Science and Engineering Beijing University of TechnologyBeijing 100124China

The Mg–12Gd–1Er–1Zn–0.9 Zr(wt%)alloy with ultra-high strength and ductility was developed via hot extrusion combined with pre-deformation and two-stage aging *** age-hardening behavior and microstructure evolution were ***-deformation introduced a large number of dislocations,resulting in strain hardening and higher precipitation strengthening in the subsequent two-stage *** a result,the alloy showed a superior strength–ductility balance with a yield strength of 506 MPa,an ultimate tensile strength of 549 MPa and an elongation of 8.2%at room *** finer and denserβ’precipitates significantly enhanced the strength,and the bimodal structure,smallβ-Mg5RE phase as well as denseγ’precipitates ensured the good ductility of the *** is suggested that the combination of pre-deformation and two-stage aging treatment is an eff ective method to further improve the mechanical properties of wrought Mg alloys.

关键词： Magnesium alloys Pre-deformation Two-stage aging Precipitation strengthening Mechanical properties

Hot deformation behaviors and processing maps of Mg-Zn-Er alloys based on Gleeble-1500 hot compression simulation

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Transactions of Nonferrous Metals Society of China 2016年第12期26卷 3123-3134页

作者： Cui-cui SUN Ke liU Zhao-hui WANG shu-bo li Xian DU Wen-bo DU College of Materials Science and Engineering Beijing University of Technology Beijing 100124 China

The hot deformation behaviors of as-solution Mg?xZn?yEr alloys (x/y=6, x=3.0, 4.5 and 6.0; y=0.50, 0.75 and 1.00) wereinvestigated on Gleeble?1500 thermal simulator in a temperature range of 200?450 °C at a strain rate of 0.001?1 s?1. The truestress?strain curves showed the dynamic competition between the working hardening and working softening mainly due to thedynamic recrystallization (DRX) occurring during hot compression. The constitutive equations were constructed which couldaccurately predict the peak stress of the alloys. The addition of Zn and/or Er resulted in higher deformation activation energy forMg?3Zn?0.5Er (alloy A). The processing maps were constructed as function of the temperature and the strain rate, providing theoptimum hot working conditions (i.e., at strain of 0.3, Mg?3Zn?0.5Er (alloy A): 380?430 ?C, <0.1 s?1; Mg?4.5Zn?0.75Er (alloy B):380?450 ?C, 0.01?0.1 s?1; Mg?6Zn?1Er (alloy C): 390?440 ?C, 0.01?0.1 s?1). The as-solution treated Mg?4.5Zn?0.75Er (alloy B)demonstrated more optimum hot working window comparing with Mg?3Zn?0.5Er (alloy A) and Mg?6Zn?1Er (alloy C).

关键词： Mg-Zn-Er alloy compression behavior microstructure evolution constitutive equations processing map

Dual phases strengthening behavior of Mg-10Gd-1Er-1Zn-0.6Zr alloy

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Transactions of Nonferrous Metals Society of China 2020年第3期30卷 635-646页

作者： lin-yue JIA Wen-bo DU Zhao-hui WANG Ke liU shu-bo li Zi-jian YU College of Materials Science and Engineering Beijing University of TechnologyBeijing 100124China

The microstructure evolution and strengthening mechanisms of Mg-10Gd-1Er-1Zn-0.6Zr(wt.%) alloy were focused in the view of the size parameters and volume fraction(fp) of dual phases(long period stacking ordered(LPSO) structures and β’ precipitates).Results show that two types of LPSO phases with different morphologies formed,and the morphology and size of both LPSO phases varied with the solution ***,the volume fraction decreased monotonously with increasing solution temperature,which in turn raised the volume fraction of β’ phase during *** alloy exhibited an ultimate tensile strength of 352 MPa,a yield strength of 271 MPa,and an elongation of 3.5% after solution treatment at 500℃ for 12 h and aging at 200℃ for 114 *** contrast to the LPSO phase,the β’ phase seems to play a more important role in enhancing the yield strength,and consequently,a decreased fLPSO/fβ’,ratio results in an increased yield strength.

关键词： magnesium alloys heat treatment long period stacking ordered(LPSO) structures precipitate mechanical properties

Effects of secondary phases on texture and mechanical properties of as-extruded Mg-Zn-Er alloys

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Transactions of Nonferrous Metals Society of China 2018年第5期28卷 890-895页

作者： Ke liU Jin-xue liU shu-bo li Zhao-hui WANG Wen-bo DU Qing-feng WANG College of Materials Science and Engineering Beijing University of Technology Beijing 100124 China Huadian Electric Power Research Institute Beijing 100124 China

The effects of kinds of secondary phases on texture and mechanical properties of Mg-Zn-Er alloys were investigated. The results suggest that the I-phase has a great effect on modification of the texture via the discontinuous dynamic recrystallization mechanism（DDRX）, which tends to form well-developed equiaxed recrystallized grains. Meanwhile, the W-phase plays an important role in refining the grain size via continuous dynamic recrystallization（CDRX）, companied with a higher maximum texture intensity. Thus, the Mg-6Zn-1 Er alloy containing I-phase shows a performance of higher elongation of 20.4%. The Mg-2Zn-2Er alloy including W-phase displays a better tensile strength, and the yield strength（YS） is about 247 MPa.

关键词： Mg-Zn-Er alloy dynamic recrystallization texture tensile properties