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Regulation of bimodal structure and mechanical properties of powder-thixoformed GO/ZK60 magnesium matrix composite through adjusting GO content

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Journal of Materials Science & Technology 2023年第31期162卷 74-89页

作者： Lingyun Wang Tijun Chen State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou 730050China

Although remarkable strength enhancements can be achieved in graphene oxide(GO)/graphene nanoplatelets(GNPs)reinforced Mg matrix composites by using the available techniques,their ductility is always quite poor due to the difficultly avoided strength-ductility *** conquer this dilemma,GO/ZK60 composites with bimodal-grain structure were fabricated using powder thixoforming in this *** results indicate that the grain size and volume fraction of coarse grains(CGs)first decrease as the GO content increases to 0.2 wt.%and then increase again as the content increases to 0.3 wt.%,while the grain size in the fine grains(FGs)almost does not ***,the strength of the composites is improved with increasing GO content and reaches the peak values at the content of 0.2 wt.%.The composite with 0.1 wt.%GO content exhibits significantly increased tensile yield strength up to 177±2 MPa while maintaining a high elongation of 23.1%±2.5%,being equivalent to that of the ZK60 matrix *** increased FGs volume fraction,together with the promoted dislocation accumulation and storage via GO and grain refinement of large-sized CGs lead to the improvement of strain hardening ability,thus rendering the composite an excellent ***,the deformation of the GO/ZK60 composites occurs progressively from the FGs to the CGs,which is opposite to the status of the milled ZK60 matrix *** view of the microstructure characteristics of the composites,a new complex calculation model was proposed and it could well predict the strength of the bimodal GO/ZK60 *** study provides a new insight into the microstructure design and fabrication technology of GO/GNPs reinforced metal-based composites with high strength and ductility.

关键词： Graphene oxide Bimodal structure Magnesium matrix composites Mechanical properties Powder thixoforming

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Formation of intermetallic compounds during reaction between Ti and Al-Mg alloys with various Mg contents

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Journal of Materials Science & Technology 2023年第28期159卷 225-243页

作者： Min Gao Tijun Chen State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou 730050China

The reactions between Ti and Al-Mg alloys were systematically investigated by heating the Ti/Al-Mg al-loy powder mixture compacts with Mg contents ranging from 5.09 to 40.36 wt.%at 660°*** element in the Al-Mg alloys contributed to the breakage of the oxide films on the surfaces of the Ti and Al-Mg alloy powders,thus,promoting the *** the samples with Mg contents varying from 5.09 wt.%to 25.93 wt.%,the first-formed intermetallic compound was Al_(18)Ti_(2)Mg_(3),and then Al_(3)Ti generated at the Al_(18)Ti_(2)Mg_(3)/Ti *** the Mg content in the Al-Mg melts decreased during the subsequent heat-ing process,the previously formed Al_(18)Ti_(2)Mg_(3)in the Ti/Al-5.09Mg sample transformed into Al_(3)Ti accom-panied by the reaction of Al with Ti to newly form Al_(3)Ti,generating a single Al_(3)Ti *** contrast,the new formation of Al_(3)Ti and its transformation to Al_(18)Ti_(2)Mg_(3)proceeded continuously in the Ti/Al-13.54Mg and Ti/Al-25.94Mg samples,resulting in a mixture of Al_(18)Ti_(2)Mg_(3)and a little Al_(3)Ti *** the Ti/Al-40.54Mg sample,Al_(3)Ti was the unique reaction product throughout the heating *** final Al_(3)Ti particles in the Ti/Al-5.09Mg sample were in a blocky shape,while they were in a plate-like form in the Ti/Al-40.54Mg sample,which was caused by the enhanced growth anisotropy due to the de-creased interfacial energy between Al_(3)Ti particles and Al-Mg melts with the increase of Mg content.A twin plane re-entrant mechanism was suggested for the growth of Al_(18)Ti_(2)Mg_(3)particles,weakening the anisotropic growth caused by the directional supply of Ti atoms,and contributing to the blocky mor-phology of Al_(18)Ti_(2)Mg_(3)*** addition,the volume difference between the formed Al_(18)Ti_(2)Mg_(3)and consumed Ti was greater than that between the Al_(3)Ti and Ti,and the Al_(18)Ti_(2)Mg_(3)has worse plasticity than the Al_(3)Ti,resulting in the Al_(18)Ti_(2)Mg_(3)reaction product fracturing more easily d

关键词： Mg content Intermetallic compound Phase transformation Morphology Twin

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Extraction and recycling technologies of cobalt from primary and secondary resources:A comprehensive review

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International Journal of Minerals,Metallurgy and Materials 2024年第4期31卷 628-649页

作者： Yukun Huang Pengxu Chen Xuanzhao Shu Biao Fu Weijun Peng Jiang Liu Yijun Cao Xiaofeng Zhu ZhongYuan Critical Metals Laboratory Zhengzhou UniversityZhengzhou 450001China State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou 730050China

Cobalt has excellent electrochemical,magnetic,and heat *** a strategic resource,it has been applied in many hightech ***,the recent rapid growth of the battery industry has substantially depleted cobalt resources,leading to a crisis of cobalt resource *** paper examines cobalt ore reserves and distribution,and the recent development and consumption of cobalt resources are summarized as *** addition,the principles,advantages and disadvantages,and research status of various methods are discussed *** can be concluded that the use of diverse sources(Cu-Co ores,Ni-Co ores,zinc plant residues,and waste cobalt products)for cobalt production should be enhanced to meet developmental ***,in recovery technology,the pyro-hydrometallurgical process employs pyrometallurgy as the pretreatment to modify the phase structure of cobalt minerals,enhancing its recovery in the hydrometallurgical stage and facilitating high-purity cobalt ***,it represents a promising technology for future cobalt ***,based on the above conclusions,the prospects for cobalt are assessed regarding cobalt ore processing and sustainable cobalt recycling,for which further study should be conducted.

关键词： cobalt recovery copper-cobalt ore nickel-cobalt ore zinc plant residue waste cobalt products

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Effects of a novel refiner Al-3Ti-4.35La combined with Sr on microstructure and mechanical properties of as-cast A356 alloy

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China Foundry 2024年第6期21卷 641-650页

作者： Mei Xu Wan-wu Ding Li-wen Hu Shi-hao Chen Hai-xia Zhang Hai-cun Yu Wen-jun Zhao School of Materials Science and Engineering Lanzhou University of TechnologyLanzhou 730050China State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou 730050China

It is a practically significant issue to refine and modify industrial Al-Si casting alloy to improve its *** the present study,a novel refiner Al-3Ti-4.35La alloy,prepared by a melt-reaction method,was used,combined with Sr to refine the as-cast A356 *** effects on the as-cast microstructures and mechanical properties of A356 alloy were *** results indicate that the combined addition of Al-3Ti-4.35La intermediate alloy and Sr can improve the microstructure and enhance the mechanical properties of A356 *** adding 0.3wt.%Al-3Ti-4.35La and 0.03wt.%Sr to the as-cast A356 alloy,the average grain size ofα-Al decreases from 693.47μm to 264.13μm(a decrease of 61.91%),the secondary dendrite arm spacing(SDAS)is decreased by 47.8%from 32.09μm to 16.75μm,and the eutectic Si is transformed from an acicular structure to short rods and a granular *** ultimate tensile strength(UTS)and elongation(EL)of the as-cast A356 alloy modified by Al-3Ti-4.35La and Sr reach 216.3 MPa and 10.6%,which are enhanced by 29.54%and 134.66%compared with the unmodified alloy,*** fracture mode is transformed from transgranular fracture to intergranular fracture,and the ductile toughness of the alloy is *** adding the Al-3Ti-4.35La and Sr,the undercooling for the nucleation ofα-Al and eutectic Si increases,leading to an accelerated nucleation rate and an increased number of nuclei,which shortens the duration of the eutectic reaction and consequently inhibits grain growth.

关键词： A356 alloy Al-3Ti-4.35La Sr refiner grain refinement microstructure mechanical properties

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Micro-strain regulation strategy to stabilize perovskite lattice based on the categories and impact of strain on perovskite solar cells

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Journal of Energy Chemistry 2025年第1期100卷 578-604页

作者： Caixia Li Wenwu Liu Shiji Da Lingbin Kong Fen Ran State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou 730050GansuChina School of Materials Science and Engineering Lanzhou University of TechnologyLanzhou 730050GansuChina

Photovoltaic metal halide perovskite solar cells(PSCs) convert light to electricity more efficiently than crystalline silicon cells, and the cost of materials used to make them is lower than that of silicon *** efficiency is not a core issue affecting the application of perovskite solar cells in special *** present, stability is the major technical encounters that hinders its further commercial development. Microstrain in PSCs is currently a significant factor responsible for the device's instability. Strain-induced ion migration is widely believed to accelerate perovskite degradation even when external stimuli are ***, it is imperative to study strain to enhance the stability of PSCs. This paper reviews recent developments to understand strain's origin and effect mechanisms on performance of PSCs, including ion migration,failure behavior, defect formation, and its effect on photoelectric properties, stability, and ***, several well-known strain management strategies are systematically introduced based on the strain effect mechanism and strain engineering on the film, providing more clues for further preparation with increased stability. The manipulation of external physical strain applied from films to entire devices has been extensively studied. Furthermore, recommendations for future research directions and chemical approaches have been provided. It is emphasized that strain engineering plays a crucial role in improving the efficiency and longevity of PSCs. Tensile strain causes rapid degradation, while moderate compressive strain and external strain control could improve properties and stability. Efforts should focus on controlling compressive strain to mitigate residual tensile strain and introducing it in a controlled manner. Future research endeavors may focus on exploring these pathways to improve the efficiency and lifespan of PSCs.

关键词： Halide perovskite solar cells Strain origins Strain effects Strain management

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Simultaneously improving the strength and ductility of AZ91/GNPs composites through decorating graphene nanoplatelets with MgO

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Journal of Materials Science & Technology 2024年第16期183卷 133-151页

作者： Pingbo Wang Jun Shen Tijun Chen Jiqiang Ma Qinglin Li Shaokai Zheng State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals Lanzhou University of TechnologyLanzhou 730050China

Magnesium matrix composites(MgMCs)have always suffered low strengthening efficiency and poor ductility due to the difficulties in pursuing the well-bonded ***,graphene nanoplatelets(GNPs)were decorated with magnesium oxide nanoparticles(MgO NPs)through chemical co-precipitation and then incorporated into AZ91 alloy to fabricate MgMCs via powder *** effect of MgO on the interface of the Mg/graphene system was investigated based on the first-principles calculations,and the result indicated that modifying GNPs with MgO NPs was helpful in improving the Mg-GNP interface *** interface structural analysis revealed that the MgO NPs were firmly bonded with both GNPs andα-Mg through the distortion area bonding and semi-coherent interfacial bonding,severing as a bridge to fasten the interface bonding of *** addition,the MgO NPs on GNPs acted as a barrier to prevent GNPs from seriously reacting with the AZ91 *** a result,the AZ91/MgO@GNPs composite was endowed with enhancements of 31%and 10%in the yield strength,and increments of 71%and 61%in elongation compared with the AZ91 alloy and AZ91/GNPs composite,respectively,exhibiting a more significant potential in optimizing the strength-toughness tradeoffcompared with the AZ91/***,the possible strengthening and toughening mechanisms were also discussed in *** work offers a relatively novel surface modification strategy to modulate the Mg-GNP interface for a simultane-ous improvement of strength and ductility.

关键词： Graphene nanoplatelets Magnesium oxide First-principles calculations Magnesium matrix composites Powder thixoforging

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Effect of surface layer softening from previous electrochemical corrosion on electrochemical cold drawing of Q235 steel bar

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Journal of Iron and Steel Research International 2022年第5期29卷 819-835页

作者： J.L.Guo T.J.Chen State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou730050GansuChina

The effects of H_(2)SO_(4)concentration and current in electrochemical corrosion on surface layer softening or plasticizing of Q235 steel bar and their effects on subsequent electrochemical cold drawing(ECD)were *** results indicate that the electrochemical corrosion can soften or plasticize the surface layer of Q235 steel bar and then make the subsequent ECD be conducted more *** softening degree and thickness of the surface layer are continuously enhanced with increasing corrosion rate,i.e.,increasing H_(2)SO_(4)concentration or current,due to the generation of more vacancy clusters in deeper regions of surface *** vacancy clusters then relax dislocations through being absorbed during ECD,and the formation and movement of additional dislocation flux are thereby enhanced,resulting in the further obvious decrease in the drawing *** is also due to the enhanced formation and movement of additional dislocation flux that the dislocation density and thus the hardness of the surface layer are decreased,as well as that the texture structure is *** behaviors are enhanced as the corrosion rate increases.

关键词： Electrochemical corrosion Electrochemical cold drawing Surface layer softening Vacancy Additional dislocation flux

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Effect of La addition on semi-solid microstructure evolution of Mg-7Zn magnesium alloy

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China Foundry 2022年第5期19卷 403-410页

作者： Zhan-yu Zhang Xiao-feng Huang Fan Yang Sheng Zhang Jiao-li Fu State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou 730050China

Semi-solid billets of Mg-7Zn and Mg-7Zn-0.3La alloys were prepared by semi-solid isothermal heat *** effects of the La element on the as-cast and semi-solid microstructures of Mg-7Zn alloy were ***,the effects of isothermal temperature and holding time on the evolution of the semi-solid microstructure of Mg-7Zn-0.3La alloy were also *** indicate that the addition of a small amount of La can significantly refine the as-cast and semi-solid *** the semi-solid thermal transformation,the size and shape factor of solid particles decrease at first and then increase with the increase of isothermal temperature and holding *** semi-solid microstructure of Mg-7Zn-0.3La alloy obtained by holding at 605℃ for 30 min is the *** average size of solid particles,shape factor,and solid fraction are 42μm,1.45 and 61.8%,*** the same time,a comparative study on the coarsening process of particles in the semi-solid billets of Mg-7Zn and Mg-7Zn-0.3La alloys reveals that the addition of La effectively decreases the coarsening rate of solid particles and restricts the growth of solid particles.

关键词： magnesium alloy La element semi-solid microstructure evolution coarsening rate constant

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Efficient fabrication of semisolid nondendritic Al alloy slurry with high quality

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China Foundry 2022年第2期19卷 117-130页

作者： Zong-xu Zhang Ti-jun Chen Kun Liu Han Xue Jia-chen Qi Guang-li Bi Ying Ma State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou 730050China

Subjecting a normal mechanical vibration to a cooling slope plate,is a proposed method for preparing semisolid nondendritic slurry,named shear-vibration coupling sub-rapid solidification(SCS).Taking Al-8Si alloy as model material,the temperature field and distribution field of solid or liquid phase during SCS were simulated using COMSOL Multiphysics software to primarily choose the optimal processing ***,the slurries were prepared with the parameters selected according to the simulation results and the microstructures of the slurries were experimentally *** indicate that the simulation results could provide a basis for roughly choosing the processing parameters,although the calculated solid fractions are always higher than the experimental *** processing parameters affect the primary grain size,shape factor and solid fraction mainly through altering the contact duration of melt on the plate,and thus affecting the cooling effect on the melt,nucleation rate,and grain dissociation and *** with optimized processing parameters show that the primary grains in the slurry have an average size of about 32μm and shape factor of 1.38,and are quite uniform,even at the highest pouring rate of 2.81 kg·s^(-1),the size and shape factor are about 46μm and 1.7,respectively,which implies that the proposed SCS is a promising technology for efficient fabrication of high-quality Al slurry available for engineering applications.

关键词： semisolid nondendritic slurry semisolid forming simulation primary grains shape factor

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Self-sensing tribological coating with phosphor particles for wear indicator

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Rare metals 2023年第7期42卷 2462-2469页

作者： Ling He Xue-Yan Wu Wen-Sheng Li Mi-Na Zhang Shu-Jie Liu State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of TechnologyLanzhou730050China School of Materials Science and Engineering Lanzhou University of TechnologyLanzhou730050China

Monitoring of coating health was achieved by embedding sensor materials(MAl_(2)O_(4):Eu^(2+),Dy^(3+),M=Sr,Ba)in tribological *** the luminescence disappears under ultraviolet(UV)light,it means that the functional coating is worn out and that recoating is *** this work,four types of alloy(Cu-14Al-X,Cu,Cu-Al,Al)composite coatings were investigated by vacuum pres sure-as sis ted sintering *** composite coatings with different copper-aluminium alloy matrixes were compared by phase composition,microstructure,luminescence properties and tribological *** results indicate that the Cu-14Al-X matrix composite coating shows not only good resistance to wear but also exhibits strong green light emitting under ultraviolet(UV)*** is the best wear-resistant self-sensitive coating which has potential industrial *** the coating wore or broke,the emitting intensity will decrease or disappear.

关键词： Copper-aluminium alloy coatings Luminescent powders Wear indicator Luminescent spectroscopy Tribology

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