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Effects of Zinc and Calcium Concentration on the Microstructure and Mechanical Properties of Hot-Rolled Mg–Zn–Ca Sheets

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Acta Metallurgica Sinica(English Letters) 2016年第2期29卷 205-216页

作者： Jun Luo Hong Yan Nan Zheng Rong-Shi Chen The group of magnesium Alloys and Their applications Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China University of Chinese Academy of Sciences Beijing 100049China

Four kinds of Mg alloys with different Zn and Ca concentration were selected to analyze the effect of Zn and Ca concentration on the microstructure and the mechanical properties of Mg-Zn-Ca alloys. It was found that Zn and Ca concentration has a great influence on the volume fraction, the morphology and the size of second phase. The Mg-1.95Zn- 0.75Ca （wt%） alloy with the highest volume fraction, continuous network and largest size of Ca2Mg6Zn3 phase showed the lowest elongation to failure of about 7%, while the Mg-0.73Zn-0.12Ca （wt%） alloy with the lowest volume fraction and smallest size of Ca2Mg6Zn3 phase showed the highest elongation to failure of about 37%. It was suggested that uniform elongations of the Mg-Zn-Ca alloys were sensitive to the volume fraction of the Ca2Mg6Zn3 phases, especially the network Ca2Mg6Zn3 phases; post-uniform elongations were dependent on the size of the Ca2Mg6Zn3 phase, especially the size of network Ca2Mg6Zn3 phase. Reduction in Zn and Ca concentration was an effective way to improve the room- temperature ductility of weak textured Mg-Zn-Ca alloys.

关键词： Mg-Zn-Ca alloys Ductility Hot rolling Texture Second phase

Creep Behavior and Microstructure Evolution of Sand–Cast Mg–4Y–2.3Nd–1Gd–0.6Zr Alloy Crept at 523–573 K

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Journal of Materials Science & Technology 2017年第1期33卷 79-89页

作者： Y.H.Kang H.Yan R.S.Chen The group of magnesium Alloys and Their applications Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China University of the Chinese Academy of Sciences Beijing 100049China

High temperature tensile-creep behavior of Mg-4Y-2.3Nd-IGd-O.6Zr （wt%, WE43（T6）） alloy at 523- 573 K was investigated. The creep stress exponent is equal to 4.6, suggesting the underlying dislocation creep mechanism. The activation energy is （199 _＋ 23） kJ/mol, which is higher than that for self- diffusion in Mg and is believed to be associated with precipitates coarsening or cross slip. The creep mechanism is further suggested to be dislocation climb at 523 K, while a cross slip at 573 K is possible. The metastable 13＇ and ~]1 phases in the WE43（T6） alloy were relatively thermal stable at 523 K and could be effective to hinder the dislocation climb, which contributed to its excellent creep resistance. However, at 573 K it readily transforms into equilibrium/3e phase and coarsens within two hours, thereby causing a decrease of creep resistance. In addition, precipitate free zones approximately normal to applied stress direction （directional PFZs） developed during the creep deformation, especially at 573 K. Those zones became preferential sites to nucleate, extend and connect microcracks and cavities, which lead to the intergranular creep fracture. Improving the thermal stability of precipitates or introducing thermally stable fine plate-shaped precipitates on the basal planes of Mg matrix could enhance the high temperature creep resistance.

关键词： WE43 alloy Creep PFZs Precipitate Fracture

Twin-roll strip casting of magnesium alloys in China

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中国有色金属学会会刊：英文版 2008年第A01期18卷 7-11页

作者：丁培道潘复生蒋斌王健李华伦吴江才许月旺文钰 National Engineering Research Center for magnesium Alloys Chongqing University Shanxi Wenxi Yinguang magnesium group Co.Ltd.

The development status of twin-roll strip casting for magnesium alloys in China was summarized as well as the new progress when several kinds of twin-roll strip casting technologies were developed and *** twin-roll casting (HTRC) of magnesium alloys has attracted much attention and has been industrialized in *** twin roll casting(VTRC) of the magnesium alloys can reach a speed of higher than 30 m/min and its research and development are just beginning and exhibit exciting *** comparing the process characteristics of the two technologies,the process stability of HTRC for the magnesium alloys is better,and the casting speed and the cooling rate of VTRC for the magnesium alloys are *** quality of the products by the two technologies needs to be improved and further investigated.

关键词：镁合金铸造工艺发展双辊挤压机

Microstructure and texture optimization by static recrystallization originating from {10-12} extension twins in a Mg-Gd-Y alloy

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Journal of Materials Science & Technology 2020年第24期59卷 44-60页

作者： S.H.Lu D.Wu R.S.Chen En-hou Han The group of magnesium Alloys and Their applications Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

During the deformation of Mg alloys,{10-12}extension twin often contributes to the formation of basal texture but rarely assists the nucleation of recrystallization,i.e.,effective grain refinement,therefore it seems to make against the improvement of formability and mechanical *** this work,{10-12}extension twin has been creatively utilized as a preference nucleation site for static recrystallization(SRX),achieving grain refinement and orientation randomization in a Mg-Gd-Y alloy using multi-directional impact forging(MDIF)and subsequent annealing *** of{10-12}extension twin on SRX behavior has been investigated by annealing treatment at 450℃using quasi-in-situ optical microscopy(OM)and quasi-in-situ electron back-scattering diffraction(EBSD).The microstructural evolution during annealing shows that several SRX gains can nucleate from the grain boundary of untwinned grains,but they only have few influences on the final microstructure due to their limited volume faction and sluggish *** contrast,a large number of SRX gains can initiate from{10-12}extension twin and grow up without the confine of twin ***,they consume their parent grains and make the main contribution to grain *** should be attributed to those pinned{10-12}twin boundary,by interacting with various dislocation slips during the MDIF process,which can operate like grain boundary,store enough strain energy,and promote the nucleation of SRX during *** the other hand,SRX grains usually keep initial random orientation and further randomize the forging texture during annealing treatment.

关键词： Mg-Gd-Y alloy Multi-directional impact forging(MDIF) {10-12}extension twin Quasi-in-situ electron back-scattering diffraction(EBSD) Static recrystallization(SRX)

Effect of solute atom concentration and precipitates on serrated flow in Mg-3Nd-Zn alloy

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Journal of Materials Science & Technology 2018年第7期34卷 1236-1242页

作者： W.H.Wang D.Wu R.S.Chen X.N.Zhang State Key Laboratory of Metal Matrix Composites School of Materials Science and Engineering Shanghai Jiao Tong University The group of magnesium Alloys and Their applications Institute of Metal Research Chinese Academy of Sciences

Influence of solute atom concentration and precipitates on serrated flow, i.e., Portevin-Le Chatelier effect, was studied in Mg-3Nd-Zn alloy by tensile test at 250℃ with a strain rate of l x 10^-3 s^-1 Microstructure and tensile property of the Mg-3Nd-Zn alloy in solution and aging conditions were also investigated. Results indicate that the serrated flow was weakened with aging time, and geometry of the serrations changed from sharp to rounded corner. Through analyzing the mechanism of the interactions between dislocations and solute atoms, it was identified that the precipitates did not only weaken the serrated flow due to the decrease in the concentration of solute atom, but also regulate the serration type by restraining the movement of dislocations during high temperature deformation.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

关键词： magnesium alloy Serrated flow Precipitate Heat treatment Deformation behavior

Enhanced tensile properties in a Mg-6Gd-3Y-0.5Zr alloy due to hot isostatic pressing(HIP)

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Journal of Materials Science & Technology 2019年第9期35卷 1860-1868页

作者： B. Zhoua D.Wu R.S.Chen En-hou Han The group of magnesium Alloys and Their applications Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

Hot isostatic pressing (HIP) was applied to Mg-6Gd-3Y-0.5Zr (GW63) alloy to reduce shrinkage porosity, thus, to enhance the integrity and reliability of castings. During HIP process, shrinkage porosity was closed by grain compatible deformation and subsequent diffusion across the bonding interface. The amount of initial shrinkage porosity was the key factor for shrinkage porosity closure. HIP was testified to be effective on shrinkage porosity reduction in GW63 alloy due to its relatively narrow solidification range and resultant low content of initial shrinkage porosity in most sections, leading to higher tensile properties both in as-cast and cast-T6 condition. The improvement in tensile properties was mainly because of shrinkage porosity reduction and resultant effective rare-earth (RE) elements homogenization and precipitation strengthening.

关键词： Hot isostatic pressing Mg-Gd-Y-Zr Shrinkage porosity reduction Tensile properties

Effect of heat treatment on the microstructures and mechanical properties of the sand-cast Mg-2.7Nd-0.6Zn-0.5Zr alloy

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Journal of magnesium and Alloys 2014年第1期2卷 20-26页

作者： D.Wu Y.Q.Ma R.S.Chen W.Ke the group of magnesium and their applications Institute of Metal ResearchChinese Academy of Sciences62 Wencui RoadShenyang 110016China

The tensile testing bars of the Mg-2.7Nd-0.6Zn-0.5Zr(wt.%)alloy were prepared by sand *** effect of solution temperature and aging time on the microstructures and mechanical properties were *** as-cast alloy was composed ofαmagnesium matrix and Mg12Nd eutectic *** solution treatment at 500℃ for 18 h,the volume fraction of eutectic compounds decreased from∼7.8%to∼2.3%,and some small Zr-containing particles were observed to precipitate at grain *** the solution temperature increased to 525℃ for 14 h,most of the eutectic compounds dissolved into the ***-aged at 200℃ for 12 h,fineβ″particles was the dominant strengthening *** yield strength,ultimate tensile strength and elongation in the peak-aged condition were 191 MPa,258 MPa and 4.2%,***,the Mg-2.7Nd-0.6Zn-0.5Zr alloys under different heat treatment conditions exhibited different tensile fracture modes.

关键词： magnesium alloy Sand-cast Heat treatment Microstructure Mechanical properties

Effect of pre-induced twinning on microstructure and tensile ductility in GW92K magnesium alloy during multi-direction forging at decreasing temperature

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Journal of magnesium and Alloys 2014年第4期2卷 287-292页

作者： S.Q.Li W.N.Tang R.S.Chen W.Ke The group of magnesium Alloys and Their applications Institute of Metal Research Chinese Academy of Sciences62 Wencui RoadShenyang 110016China

Effect of pre-induced twinning on the microstructure evolution and mechanical properties of extruded Mg-9.26Gd-2.08Y-0.36Zr(GW92K)alloy have been investigated during multi-direction forging with large strains at decreasing temperature from 400℃ to 300℃.The results showed that,whether there pre-induced twinning existing in the initial microstructure by pre-deformation or not,a mixed microstructure of residual coarse grains and notably refined grains formed under both conditions,combing with some residual coarse grains with less deformation inside grains and lots of dispersed nano-precipitates distributed along refined grain ***,a significant improvement with the tensile ductility was obtained by the pre-induced twinning in the former *** was suggested that,the pre-induced twinning largely contributed to the grain refinement and lead to an increase in the ratio of fine grain structure which would be responsible for the better ***,during subsequent forging deformation in the pre-deformed sample,the grain refinement mechanism by gradual grain orientation rotation around the surface section in residual coarse-grains was a little different from that by the macro-shear deformation in the as-extruded condition.

关键词： magnesium alloy Pre-induced twinning Multi-directional forging Refined-grain microstructure Tensile ductility

Effect of Solution Treatment on the Microstructure and Mechanical Properties of Sand-Cast Mg–9Gd–4Y–0.5Zr Alloy

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Acta Metallurgica Sinica(English Letters) 2018年第2期31卷 189-198页

作者： Jing-Li Li Na Zhang Xiao-Xuan Wang Di Wu Rong-Shi Chen The group of magnesium Alloys and Their applications Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering University of Science and Technology of China Hefei 230026 China AVIC Shenyang Liming Aero--Engine group Corporation Shenyang 110043 China

Sand-cast Mg–9Gd–4Y–0.5 Zr（wt%） alloy was solution-treated at 500–565 ℃ in the time range of 0.5–30 h in air or vacuum to investigate its microstructure evolution and mechanical properties. The results showed that solution treatment temperature had a significant influence on the dissolving rate of eutectic phase and grain growth. Taken both of them into consideration, 510–520 ℃ was considered to be the optimum solution treatment temperature range for this *** should be noted that the trace（0.4–0.9 vol%） and insoluble cuboid-shaped phase precipitated during solution treatment was identified to be YH2, of which the hydrogen was thought to come from both the melting and solution heating *** addition, the 3D morphology and dissolving process of Mg24（Gd,Y）5 eutectic phases in the as-cast alloy were also discussed via in-situ observation under X-ray tomography.

关键词： Mg-Gd-Y-Zr alloy Solution treatment Microstructure Rare-earth hydride