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Microstructure,texture and mechanical behavior characterization of hot forged cast ZK60 magnesium alloy

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Journal of Materials science & Technology 2017年第9期33卷 907-918页

作者： s.M.h.Karparvarfard s.K.shaha s.b.behravesh h.Jahed b.w.williams Department of Mechanical & Mechatronics Engineering University of Waterloo Canmet MATERIALs Natural Resources Canada

structure with a significant reduction in casting porosity, while the texture changed to sharp basaMeasured mechanical properties of the forged alloy showed that strength did not change, howductility improved by 75%. The analysis of the fracture surface of the forged alloy under tension rea ductile fracture with dimple morphology, while the as-cast alloy displayed a brittle fracture with pores. This demonstrated that the reduction of casting defects and dendritic morphology, as well evolution of recrystallized grains, enhanced ductility, while partial dynamic recrystallization throuforging process resulted in only marginal modification of strength in the forged condition.. 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials sciTechno

关键词： Magnesium Forging Ductility Texture Recrystallization

Phase Formation and Magnetic Properties of Nanocomposite Nd-Fe-b Adjusted by small Amount of Dy and Co

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Journal of Rare Earths 2004年第z2期22卷 89-94页

作者： T s Jang T w Lim h s Aum D h Lee M b Kim Division of Materials and Chemical Engineering Sun Moon UniversityKorea Division of Materials and Chemical EngineeringSun Moon UniversityKorea Division of Mechanical EngineeringSun Moon University 100 Kalsan LiTangjung MyonAsan CityChoongnam 336-708Korea Division of Materials and Chemical EngineeringSun Moon UniversityKorea Division of Materials and Chemical EngineeringSun Moon UniversityKorea

In order to improve and stabilize the magnetic properties of nanocomposite Nd2Fe14b/α-Fe magnetic alloys by a compositional adjustment, small amount of Dy and/or Co was added to Nd9Fe84b7 alloys. DTA analysis on the amorphous of the alloys took place as the soft magnetic phases were crystallized, and then the hard magnetic Nd2Fe14b was precipitated from them. while α-Fe and a metastable 1:7 (TbCu7-type) phase were formed simultaneously in Dy and Co-free alloys, they were crystallized separately at different temperatures after Dy or Co was added. This phase separation occurred more clearly in the Dy-treated alloys and the other soft magnetic phase Fe3b was also stabilized by Dy and/or Co. The 1: 7 phase that was stabilized by Dy and/or Co was not eliminated at 700 ℃, decreasing magnetic properties of the alloys. It was eventually disappeared above 725 ℃, but Fe3b was not eliminated even at 750 ℃ when Dy was added more than 0.5 at% or Co was added more than 2.0 at%. Amount of Nd2Fe14b in the alloys tended to increase as Dy addition increased,whereas Co addition did not lead to any appreciable change in the ratio of α-Fe and Nd2Fe14b. Moreover, Dy addition apparently increased coercivity of an alloy while Co addition had a beneficial effect on remanence. The grains in the Dytreated alloys were usually finer than those in the Co-treated alloys. The grain size of both α-Fe and Nd2Fe14b in the alloys exhibiting mr ≥ 0.72 was in the range of 20 ～ 40 nm or even larger 50 nm, which is larger than the theoretical optimum size ( ～ 10 nm). Typical magnetic properties obtained from a Nd7.5Dy1.5Fe82.5Co1.5b7 alloy annealed for 12 min at 725 ℃were ihc=4.85 kOe, br= 11.32 kG, (bh)max = 15.73 MGOe, and mr=0.73.

关键词： nanocomposite Nd-Fe-b magnetic properties remanence coercivity

Nanophase Decomposition of a Zn-Al based Alloy Zn_(68)Al_(10)Cu_(22)

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Journal of Materials science & Technology 2004年第6期20卷 687-690页

作者： Y.h.Zhu w.b.Lee s.To Advanced Materials Research Center Department of Industrial and systems Engineering The Hong Kong Polytechnic University Hong Kong ChinaAdvanced Materials Research Center Department of Industrial and Systems Engineering The Hong Kong Polytechnic University Hong Kong ChinaAdvanced Materials Research Center Department of Industrial and Systems Engineering The Hong Kong Polytechnic University Hong Kong China

The nanostructural evolution and phase transformation of the films of a Zn-Al based alloy (Zn68Al10Cu22 in wt pct) have been studied by using X-ray diffraction and scanning electron microscopy. Nanostructural thin films of the Zn-AI based alloy were produced by using an electron beam deposition technique. It was found that a nanocrystalline phase η'n had a strong preferred crystal orientation at (0002) crystal planes in the as-deposited films. During ageing at 220℃, the decomposition of nanophase η'n started with clustering to form Z-zones, and transitionai phase, which was accompanied by an eutectoid decomposition of the η'n phase: η'n β'eut T'. Decomposition, such as clustering and the formation of the Z-zones, and the transitionai phase etc. were observed in the nanophase β'eut. The formation and the decomposition of the transitionai phase of micrometers in size were involved in the decomposition of the main nanophase η'n. The mechanism of the Z-zones formation and the stability of nanophases were discussed.

关键词： Ageing Nanostructure Nanophase stability Zn-Al based alloy film

Influence of alloying elements on microstructure and microhardness of Mg-sn-Zn-based alloys

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Transactions of Nonferrous Metals society of China 2010年第12期20卷 2246-2252页

作者： w. L. ChENG s. PARK w. N. TANG b. s. YOU b. h. KOO school of Nano ＆ Advanced Materials Engineering Changwon National University Changwon 641-773 South Korea Light Metals Research Group Korea Institute of Materials Science （KIMS） Changwon 641-831 South Korea

The phase evolution in （88%-91%）Mg-8%sn-l%Zn-X （X=A1, Mn and/or Ce） system was analyzed via CALPhAD method and simulations were used in precise selection of the chemical composition. The influence of the addition of different alloying elements such as A1, Mn and Ce on the microstructure and microhardness of Mg-8%sn-l%Zn-based alloys was investigated. Combined addition of A1 and Mn shows features distinct from separate addition of A1 or Mn. Additions of l%AI and l%Mn to base alloy result in the formation of massive A1-Mn phase in a-Mg matrix grains. Addition of Ce element can refme the second eutectic precipitates and form intermetallic compounds with sn. Fine rod-like sn-Ce phase presents mainly on the grain boundaries and plays a role in inhibiting grain growth. The effects of alloying elements on Vickers microhardness and indentation size effect of base alloy were examined.

关键词： magnesium alloys alloying elements CALPhAD method hardness indentation size effect

Conformable fractional heat equation with fractional translation symmetry in both time and space

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Chinese Physics b 2023年第4期32卷 125-129页

作者： w s Chung A Gungor J Krız b C Lutfuoglu h hassanabadi Department of Physics and Research Institute of Natural science College of Natural ScienceGyeongsang National UniversityJinju 660-701Korea Mechanical Engineering Akdeniz UniversityAntalyaTurkey Department of Physics University of Hradec KraloveRokitanskeho 6250003 Hradec KraloveCzech Republic Department of Physics Akdeniz UniversityAntalyaTurkey Faculty of Physics Shahrood University of TechnologyShahroodIran

we investigate the fractional heat equation with fractional translation in both time and position with different fractional *** examples,we consider a rod and anα-disk with an initial constant temperature and discuss... 详细信息

关键词： fractional derivative heat equation conformable symmetry

Interface dominated deformation transition from inhomogeneous to apparent homogeneous mode in amorphous/amorphous nanolaminates

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Journal of Materials science & Technology 2022年第4期99卷 178-183页

作者： Z.Q.Chen M.C.Li J.s.Cao F.C.Li s.w.Guo b.A.sun h.b.Ke w.h.wang songshan Lake Materials Laboratory Dongguan 523808PR China Institute of Physics Chinese Academy of SciencesBeijing 100190PR China Institute of Materials Engineering Nanjing UniversityNantong 226019PR China school of Physics science and Technology Xinjiang UniversityXinjiang 830046PR China school of Physical sciences University of Chinese Academy of SciencesBeijing 100049PR China state Key Laboratory for Mechanical behavior of Material Xi'an Jiaotong UniversityXi’an 710049PR China

The amorphous/amorphous nanolaminates(A/ANLs)have aroused great attentions owing to their tunable structure and enhanced mechanical ***,the plastic deformation mechanism of A/ANLs have yet been ***,we systematically examined the mechanical properties and deformation behavior of series of NiNb/ZrCuNi Al A/ANLs via nanoindentaion *** was found that both the amount and morphology of amorphous/amorphous interface(A/AIs)played crucial roles in the plastic deformation of A/*** and straighter A/AIs facilitated multiple shear banding deformation,of which the hardness increased with decreasing layer thickness,as the A/AIs hindered the propagation of shear bands(sbs).whilst,more and wavier A/AIs promoted homogeneous deformation,of which the hardness stayed at a much lower value and was relatively irrelevant with the layer thickness,for the promoted activation of shear transformation zones by A/*** results provide guidance for modifying the mechanical properties of amorphous alloys with interface engineering design.

关键词： Amorphous alloys Nanolaminates shear bands hardness Interface

Microstructural evolution and superelastic properties of ultrafine-graine d NiTi-base d shape memory alloy via sintering of amorphous ribbon precursor

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Journal of Materials science & Technology 2023年第7期138卷 80-92页

作者： w.s.Cai h.Z.Lu h.Z.Li Z.Liu h.b.Ke w.h.wang C.Yang National Engineering Research Center of Near-net-shape Forming for Metallic Materials Guangdong Provincial Key Laboratory for Processing and Forming of Advanced Metallic MaterialsSouth China University of TechnologyGuangzhou 510640China songshan Lake Materials Laboratory Dongguan 523808China Institute of Physics Chinese Academy of SciencesBeijing 100190China

NiTi-based shape memory alloys(sMAs)are considered as cutting-edge intelligent functional ***,it remains a great challenge to obtain ultrafine-grained(UFGed)bulk materials with mm-scale size as well as outstanding superelastic ***,UFGed bulk Ti_(35)Zr_(15)Ni_(35)Cu_(15)NiTi-based sMA is successfully prepared via spark plasma sintering of amorphous ribbon precursor at different sintering temperatures,and microstructural evolution and superelastic properties are symmetrically *** is found that its grain size ranges from UFG to micro-grain with increased sintering temperature regard-less of the predominant b2 matrix in all bulk ***,the orientation relationships between b2 matrix and nano-scale fcc(Ti,Zr)_(2)Ni precipitate evolve from coherent to ***,the UFGed samples exhibit perfect superelasticity with the high recoverable strain of∼5.8%,the stable recov-ery rate above 99%,and the great critical stress inducing martensitic transformation higher than 1 GPa,far superior to the corresponding ones of suction-cast micro-grained TiZrNiCu ***,the perfect superelasticity is attributed to the good resistance to dislocation slip or grain boundary slip by residual nano-scale amorphous phase or secondary phase of coherent and semi-coherent fcc(Ti,Zr)_(2)Ni *** addition,the gentle superelastic plateau is associated to the favorable transfer stress and the strong ability to accommodate dislocation movement,which is generated by the coherent interface between nano-scale fcc(Ti,Zr)_(2)Ni and UFGed b2 *** results suggest that spark plasma sintering of amorphous alloy precursor is a feasible route to obtaining excellent superelasticity in NiTi-based sMAs.

关键词： shape memory alloy Amorphous alloy Microstructure superelasticity

Experimental and Numerical Investigation on Impact Performance of Carbon Reinforced Aluminum Laminates

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Journal of Materials science & Technology 2010年第4期26卷 327-332页

作者： s.h. song Y.s. byun T.w. Ku w.J. song J. Kim b.s. Kang National Core Research Center Pusan National University Busan 609-735 Korea Dept. of Aerospace Engineering Pusan National University Busan 609-735 Korea Industrial Liaison Innovation Cluster Pusan National University Busan 609-735 Korea

It is known that fiber metal laminates （FML） as one of hybrid materials with thin metal sheets and fiber/epoxy layers have the characteristics of the excellent damage tolerance, fatigue and impact properties with a relatively low density. Therefore, the mechanical components using FML can contribute the enhanced safety level of the sound construction toward the whole body. In this study, the impact performance of carbon reinforced aluminum laminates （CARAL） is investigated by experiments and numerical simulations. Drop weight tests are carried out with the weight of 4.7 kg at the speed of 1 and 2 m/s, respectively. Dynamic non-linear transient analyses are also accomplished using a finite element analysis software, AbAQUs. The experiment results and numerical results are compared with impact load-time histories. Also, energy-time histories are applied to investigate the impact performance of CARAL.

关键词： Fiber metal laminates (FML) Carbon reinforced aluminum laminates (CARAL) Numerical simulation Impact performance

MICROsTRUCTURAL ChARACTERIsTICs AssOCIATED wITh hIGh- sTRAIN-RATE PLAsTIC DEFORMATION IN ThE ELECTROFORMED COPPER LINER OF shAPED ChARGEs

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Acta Metallurgica sinica(English Letters) 2005年第5期18卷 620-626页

作者： A.L. Fan w.h. Tian Q. suns b.s. wang Department of Materials Physics and Chemistry University of Science and Technology Beijing Beijing 100083 China Taiyuan University of science and Technology Taiyuan 030024 China 210 Institute The Chinese Ordnance Industry Institute Beijing 100081 China

The microstructures of electroformed copper liners of shaped charges that had undergone high-strain-rate deformation were observed by optical microscopy （OM） and scanning electron microscopy （sEM）. Meanwhile, the orientation distribution of the grains in the recovered jet was examined by electron backscattering Kikuchi pattern （EbsP） technique. EbsP analysis reveals that the fibrous texture observed in the as-electroformed copper liners disappeared after explosive detonation deformation. OM observation shows that the microstructure evolves system- atically from the jet center to its perimeter during cooling from high temperatures after explosive detonation deformation. This microstructural characteristic is similar to that of solidification, i.e. there exist equiaxed grains in the center of the jet and significant columnar grains around the equiaxed grains. The result reveals that there is melting-related phenomenon in the jet center. Corresponding microhardness variations from the jet center to its perimeter is also determined. All the phenomena can be explained by a strong gradient of temperature across the section of the jet during plastic deformation at high-strain-rate.

关键词： jetting electroformation microstructure hardness,ultra-high strain rate deformation