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Journal of Magnesium and Alloys 2021年第2期9卷 456-466页

作者： Yunwei Gui Lingxiao Ouyang Yujie Cui Huakang Bian Quanan Li Akihiko Chiba Department of Materials Processing Graduate School of EngineeringTohoku University6-6-11 AobaAramakiAoba-kuSendai 980-8579Japan Institute for Materials Research Tohoku University2-1-1 KatahiraAoba-kuSendai 980-8577Japan School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang 471023China Collaborative Innovation Center of Nonferrous Metals Henan ProvinceLuoyang 471023China

We utilized electron backscatter diffraction to investigate the microstructure evolutions of a newly developed magnesium-rare earth alloy(Mg–9.80 Gd–3.78 Y–1.12 Sm–0.48 Zr)during instantaneous hot indirect *** equiaxed fine-grained(average grain size of 3.4±0.2μm)microstructure with a weak texture was *** grain refinement was mainly attributed to the discontinuous dynamic recrystallization(DDRX)and continuous DRX(CDRX)processes during the hot indirect extrusion *** twin boundaries formed during the initial deformation stage effectively increased the number of high angle grain boundaries(HAGBs),which provided sites for new grain nuclei,and hence,resulted in an improved DDRX *** with DDRX,CDRX processes characterized by low angle grain boundary(LAGB)networks were also observed in the grain interior due to effective dynamic recovery(DRV)at a relatively high temperature of 773 K and high strain ***,LAGB networks were transformed into HAGB networks by the progressive rotation of subgrains during the CDRX process.

关键词： Magnesium-rare earth(Mg-Re)alloy grain refinement Discontinuous dynamic recrystallization(DDRX) Continuous dynamic recrystallization(CDRX) Hot indirect extrusion

grain refinement of Mg-Al alloys inoculated by MgAl_(2)O_(4)powder

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Journal of Magnesium and Alloys 2021年第4期9卷 1215-1223页

作者： Hengbin Liao Meiyan Zhan Chengbo Li Zhiqiang Ma Jun Du Department of Metallic Materials School of Materials Science and EngineeringSouth China University of TechnologyWu Shan Road 381Tianhe DistrictGuangzhou 510640China

As a potent nucleating substrate forα-Mg grain,MgAl_(2)O_(4) powder was used to inoculate the Mg-Al melt in this *** effects of MgAl_(2)O_(4)amount,holding time and Al content on the grain size and grain refining ratio of the inoculated Mg-Al alloys are systematically *** results show that the minimum grain size of Mg-3Al alloy is achieved by adding 2wt.%MgAl_(2)O_(4)powder and this alloy exhibits higher grain refining ratio than Mg-5Al and Mg-8Al *** crystallographic misfit calculation indicates the wellmatching and possible orientation relationships(ORs)betweenα-Mg and MgAl_(2)O_(4).Among these predicted ORs,[10–10]α−Mg//[110]MgAl2O4 in(0002)α−Mg//(1–13)MgAl2O4 possesses the smallest misfit,i.e.,2.34%(fr).Both results of the experiment and crystallographic calculation demonstrate that the grain refinement of Mg-Al alloys is attributed to the MgAl_(2)O_(4)particles acting as the heterogeneous nucleation substrates forα-Mg grains.

关键词： grain refinement Inoculation Heterogeneous nucleation Mg-Al alloys MgAl_(2)O_(4)

grain refinement impact on the mechanical properties and wear behavior of Mg-9Gd-3Y-2Zn-0.5Zr alloy after decreasing temperature reciprocating upsetting-extrusion

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Journal of Magnesium and Alloys 2022年第12期10卷 3506-3519页

作者： Wenlong Xu Jianmin Yu Leichen Jia Chang Gao Zhan Miao Guoqin Wu Guojun Li Zhimin Zhang School of Material Science and Engineering North University of ChinaTaiyuan 030051China

Based on the deforming technique of severe plastic deformation(SPD), the grain refinement of a Mg-9Gd-3Y-2Zn-0.5Zr alloy treated with decreasing temperature reciprocating upsetting-extrusion(RUE) and its influence on the mechanical properties and wear behavior of the alloy were studied. The RUE process was carried out for 4 passes in total, starting at 0 ℃ and decreasing by 10 ℃ for each pass. The results showed that as the number of RUE passes increased, the grain refinement effect was obvious, and the second phase in the alloy was evenly distributed. Room temperature tensile properties of the alloy and the deepening of the RUE degree showed a positive correlation trend, which was due to the grain refinement, uniform distribution of the second phase and texture weakening. And the microhardness of the alloy showed that the microhardness of RUE is the largest in 2 passes. The change in microhardness was the result of dynamic competition between the softening effect of DRX and the work hardening effect. In addition, the wear resistance of the alloy showed a positive correlation with the degree of RUE under low load conditions. When the applied load was higher, the wear resistance of the alloy treated with RUE decreased compared to the initial state alloy. This phenomenon was mainly due to the presence of oxidative wear on the surface of the alloy, which could balance the positive contribution of severe plastic deformation to wear resistance to a certain extent.

关键词： Mg-9Gd-3Y-2Zn-0.5Zr alloy Reciprocating upsetting-extrusion grain refinement Texture Mechanical properties Wear behavior

grain refinement in low SFE and particle-containing nickel aluminium bronze during severe plastic deformation at elevated temperatures

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Journal of Materials Science & Technology 2021年第23期82卷 57-68页

作者： C.J.Barr K.Xia Department of Mechanical Engineering University of MelbourneVictoria3010Australia DMTC Ltd. 24 Wakefield St.HawthornVIC3122Australia

The influence of particle size and morphology on grain refinement in low stacking fault energy(SFE)alloys was studied by comparing the grain structures in single-and multi-phase Al-bronze(AB)alloys following equal channel angular pressing(ECAP)between 350 and 500℃.In particular,nickel aluminium bronze(NAB)was chosen as it contained both coarse and fine rounded particles,as well as a lamellar phase which evolved during *** refinement in the single-phase alloy was achieved through dynamic recrystallisation initiated at deformed twin *** contrast,different mechanisms were observed in the particle-containing *** around the coarseκⅡparticles(~5μm)was promoted through particle stimulated nucleation(PSN),whereas recrystallisation in the region of the fineκⅣ(~0.4μm)was delayed due to the activation of secondary *** refinement in areas of the lamellarκⅢshowed significant variation,depending on the lamellar orientation relative to the shear plane of *** the lamellae deformed,numerous high angle grain boundaries were generated between fragments and served as nucleation sites for recrystallisation,while PSN occurred around spheroidised *** spreading of theκⅢparticles by ECAP then enhanced the total area of recrystallised grains.

关键词： Equal channel angular pressing Copper alloys grain refinement Stacking fault energy Severe plastic deformation

grain refinement of Mg-3Y alloy using Mg-10Al_(2)Y master alloy

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Journal of Rare Earths 2021年第7期39卷 881-888,I0005页

作者： Zhongtao Jiang Xiang Meng Bin Jiang Shan Jiang Jiahong Dai Jingren Dong Yongfeng Ding Chongqing Key Laboratory of Materials Surface&Interface Science Chongqing University of Arts and SciencesChongqing 402160China College of Materials Science and Engineering National Engineering Research Center for Magnesium AlloysChongqing UniversityChongqing 400044China Chongqing Academy of Science and Technology Chongqing 401123China College of Mechanical and Electrical Engineering Yangtze Normal UniversityChongqing 408100China

The as-extruded Mg-10Al_(2)Y master alloy was chosen as a novel grain refiner for as-cast Mg-3Y *** samples of cast Mg-3Y alloy added with pure Al and Mg-Zr master alloy grain refiners were prepared under the same *** this study,the influence of addition amounts of Al_(2)Y and holding time on grain refinement efficiency as well as tensile properties was *** the grain refining ability of the Al_(2)Y particles was systematically evaluated in terms of the addition amounts,number density of the Al_(2)Y particles and holding *** finest grains are achieved at 2 wt% Al_(2)Y addition amount,which corresponds to number density of the polygonal Al_(2)Y particles of 420-460 mm^(-2).The Mg-10Al_(2)Y master alloy has significant refinement performance and no refining recession occurs at the holding time within 60 min,or the settling time up to 180 *** refinement and the second phase strengthening of uniformly distributed Al_(2)Y particles contribute to the simultaneous enhancement on both strength and elongation of Mg-3Y alloy.

关键词： grain refinement Al_(2)Y Mg-Y alloys Microstructure Rare earths

grain refinement of Mg-alloys by native MgO particles: An overview

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Journal of Magnesium and Alloys 2022年第11期10卷 2919-2945页

作者： Z.Fan F.Gao Y.Wang S.H.Wang J.B.Patel Brunel Centre for Advanced Solidification Technology(BCAST) Brunel University LondonUxbridgeUB83PHUK

A fine and equiaxed solidification process delivers multidimensional benefits to Mg-alloys, such as improved castability, reduced casting defects, enhanced mechanical properties, increased corrosion resistance and potential for increased recycled contents. Despite extensive research on grain refinement of Mg-alloys in the last few decades, currently, there is no effective grain refiner available for refining Mg-Al alloys, and our current understanding of grain refining mechanisms is not adequate to facilitate the development of effective grain *** the EPSRC(UK) Li ME Hub’s research program, substantial advances have been made in understanding the early stages of solidification covering prenucleation, heterogeneous nucleation, grain initiation and grain refinement. In this paper, we provide a comprehensive overview of grain refinement of Mg-alloys by native MgO particles. We show that native MgO particles can be made available for effective grain refinement of Mg-alloys by intensive melt shearing regardless of the alloy compositions. More importantly, we demonstrate that(1) the addition of more potent exogenous particles will not be more effective than native MgO;and(2) MgO particles are difficult to be made more impotent for grain refinement through promoting explosive grain initiation. We suggest that the most effective approach to grain refinement of Mg-alloys is to make more native MgO particles available for grain refinement through dispersion, such as by intensive melt shearing.

关键词： Mg-alloys grain refinement Magnesia(MgO) Nucleation grain initiation

grain refinement of 5A06 aluminum alloy welds caused by tungsten inert gas welding arc characteristics under Ar-He alternating gas supply conditions:a coupled method of water-cooled copper plate test/numerical simulation

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Journal of Iron and Steel Research International 2024年第3期31卷 767-777页

作者： Hong-bin Dai Jian Miao Jia-xin Lin School of Materials Science and Engineering Harbin University of Science and TechnologyHarbin 150040HeilongjiangChina

The welding arc,as a carrier for the conversion of electrical energy to thermal energy,has a direct impact on the quality of welding by its properties and *** the tungsten inert gas(TIG)welding process under the condition of Ar-He alternating gas supply,the arc is alternately converted between Ar arc and He arc with an alternating gas supply cycle,which has obvious arc change *** FLUENT software was used to numerically simulate the characteristics of the TIG arc under the condition of alternating gas supply,and the arc temperature field,arc pressure,electric potential and current density distribution under the condition of alternating gas supply were *** with the real-time data of arc pressure measured by the water-cooled copper plate with holes,it is proved that the TIG arc has obvious dynamic characteristics under the condition of Ar-He alternating gas *** unique dynamic TIG arc acts on the 5A06 aluminum alloy weld,causing the molten pool to stir,resulting in uniform microstructure and grain refinement at the weld,and thereby improving the mechanical properties of the welded joint.

关键词： Alternating gas supply grain refinement Numerical simulation Tungsten argon arc morphology Microstructure Mechanical property

grain refinement and orientation of AZ31B magnesium alloy in hot flow forming under different thickness reductions

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Journal of Materials Science & Technology 2018年第7期34卷 1091-1102页

作者： Yalian Zhang Fenghua Wang Jie Dong Li Jin Conghui Liu Wenjiang Ding National Engineering Research Center of Light Alloy Net Forming & State Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong University Shanghai Light Alloy Net Forming National Engineering Research Center Co. Ltd

An analysis of the hot flow forming of Mg-3.0Al-l.0Zn-0.3Mn （AZ31B） alloy was conducted by experiments and numerical simulations. The effects of different thickness reductions on the microstructure and mechanical properties were investigated at a temperature of 693 K, a spindle speed of 800 rev/min and a feed ratio of 0.1 mm/rev. Thickness reductions have great influence on the uniformity of microstructure along the radial direction （RD） and the grain sizes become refined and uniform when the thickness reduction reaches 45%. The c-axes of most grains are approximately parallel to the RD, with a slight inclination towards the axial direction （AD）. The best mechanical properties with UTS of 280 MPa and YS of 175 MPa near the outer surface while 266 MPa and 153 MPa near the inner surface have been achieved due to grain refinement and texture. Moreover, the material flow behavior and stress/strain distributions for singlepass reductions were studied using the ABAQUS/Explicit software. The calculated results indicate that the materials mainly suffer from triaxial compressive stresses and undergo compressive plastic strain in RD and tensile strains in other directions. The higher stress and strain rate near the outer surface lead to more refined grains than that of other regions along the RD, whereas the orientation of the maximum principal compressive stress leads to a discrepancy of the grain orientations in RD.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

关键词： AZ31B Hot flow forming grain refinement Texture

grain refinement mechanism of Mg-3Sn-1Mn-1La alloy during accumulative hot rolling

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Journal of Materials Science & Technology 2021年第32期91卷 251-261页

作者： Z.Y.Zhao R.G.Guan Y.F.Shen P.K.Bai School of Materials Science and Engineering North University of ChinaTaiyuan 030051China bEngineering Research Center of Continuous Extrusion Ministry of EducationDalian Jiaotong UniversityDalian 116028China Key Laboratory for Anisotropy and Texture of Materials Northeastern UniversityShenyang 110004China

We elucidate the effect of lanthanum(La) on the grain refinement of Mg-3 Sn-1 Mn alloy during accumulative hot rolling. The lath-shaped Mg_(2) Sn phase in the Mg-3 Sn-1 Mn alloy is firstly broken and spheroidized,and then the size increases and coarsens with the increase of rolling reduction, most of Mg_(2) Sn move from grain boundary to grain and are homogeneously distributed within the matrix. However, the plate-shaped Mg Sn La compound in Mg-3 Sn-1 Mn-1 La gradually becomes fine, spheroidized, and homogeneously distributed. The grain sizes of Mg-3 Sn-1 Mn and Mg-3 Sn-1 Mn-1 La alloys become fine through dynamic recrystallization(DRX), though the grain refinement of Mg-3 Sn-1 Mn-1 La alloy is better compared to the Mg-3 Sn-1 Mn alloy. A large number of uniformly distributed spherical Mg Sn La compounds pin the dislocations, thus increasing the dislocation density. Hence, the driving force for DRX increases and promotes the formation of deformation bands and more twins, providing the sites for DRX nucleation and growth.

关键词： Mg alloy grain refinement Dynamic recrystallization Accumulative hot rolling

grain refinement of Mg-Ca alloys by native MgO particles

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Journal of Magnesium and Alloys 2024年第3期12卷 980-996页

作者： Shihao Wang Yun Wang Quentin M.Ramasse Zhongyun Fan Super STEM Laboratory SciTech Daresbury CampusDaresbury WA44ADUK School of Chemical and Process Engineering University of LeedsLeeds LS29JTUK BCAST Brunel University LondonUxbridgeMiddlesex UB83PHUK

In Mg-Ca alloys the grain refining mechanism,in particular regarding the role of nucleant substrates,remains the object of *** native MgO is being recognised as a nucleating substrate accounting for grain refinement of Mg alloys,the possible interactions of MgO with alloying elements that may alter the nucleation potency have not been elucidated ***,we design casting experiments of Mg-xCa alloys varied qualitatively in number density of native MgO,which are then comprehensively studied by advanced electron *** results show that grain refinement is enhanced as the particle number density of MgO *** native MgO particles are modified by interfacial layers due to the co-segregation of Ca and N solute atoms at the MgO/Mg *** aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy,we reveal the nature of these Ca/N interfacial layers at the atomic *** of the crystallographic termination of MgO,Ca and N co-segregate at the MgO/Mg interface and occupy Mg and O sites,respectively,forming an interfacial structure of a few atomic *** interfacial structure is slightly expanded,less ordered and defective compared to the MgO matrix due to compositional deviations,whereby the MgO substrate is altered as a poorer template to nucleate Mg *** solidification in a TP-1 mould,the impotent MgO particles account for the grain refining mechanism,where they are suggested to participate into nucleation and grain initiation processes in an explosive *** work not only reveals the atomic engineering of a substrate through interfacial segregation but also demonstrates the effectiveness of a strategy whereby native MgO particles can be harnessed for grain refinement in Mg-Ca alloys.

关键词： Mg-Ca alloy grain refinement MgO Interfacial segregation STEM/EELS Solidification.