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Multistage strain-hardening behavior of ultrastrong and ductile lightweight refractory complex-concentrated alloys

Journal of Materials Science & Technology 2023年第18期149卷 73-87页

作者： Yuefei jia Chang Ren Shiwei Wu Yongkun Mu Long Xu yandong jia Wentao Yan Jun Yi Gang Wang Institute of Materials Shanghai UniversityShanghai 200444China Zhejiang Institute of Advanced Materials Shanghai UniversityJiashan 314100China Department of Mechanical Engineering National University of Singapore117575Singapore

Lightweight high-entropy alloys or complex-concentrated alloys have demonstrated great potential for engineering applications due to their high strength and ***,a weak strain-hardening ability and a limited tensile ductility remain their major ***,a multistage strain-hardening effect is developed to ensure a high strength and still a sufficient ductility in a rolled and annealed(Ti_(44)V_(28)Zr_(14)Nb_(14))_(98.5)Mo_(1.5)(at.%)lightweight refractory complex-concentrated alloy(M1.5A-LRCCA).This multistage strain-hardening behavior is related to the microstructure and the corresponding initial aver-age dislocation density and distribution by comparison with rolled and annealed Ti_(44)V_(28)Zr_(14)Nb_(14)(M0-LRCCA)and as-cast(Ti_(44)V_(28)Zr_(14)Nb_(14))_(98.5)Mo_(1.5)(M1.5C-LRCCA).The microstructure,with homogeneously distributed submicron precipitations,a moderate initial average dislocation density,and uniform disloca-tion distribution(e.g.,M1.5A-LRCCA),is susceptible to producing various deformation substructures,such as dislocation substructures(slip bands,Taylor lattices,microbands,DDWs),shear bands,and deformation twins,which results in the multistage strain-hardening *** method of achieving multistage strain hardening behavior through a microstructure modulation is significant for engineering applications of lightweight high-entropy alloys or complex-concentrated alloys,and it might be extended to other lightweight and high-strength alloys.

关键词： High-entropy alloy/complex-contracted alloy Lightweight Strain hardening BCC Mechanical properties

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Dual precipitate simultaneous enhancement of tensile and fatigue strength in(FeCoNi)_(86)Al_(7)Ti_(7) high-entropy alloy fabricated using selective laser melting

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Journal of Materials Science & Technology 2023年第17期148卷 90-104页

作者： Long Xu yandong jia Zhenhui Wang Shiwei Wu Yuefei jia Chuan Geng jianchao Peng Xiaohua Tan Gang Wang Institute of Materials Shanghai UniversityShanghai 200444China Zhejiang Institute of Advanced Materials Shanghai UniversityJiashan 314100China Department of Mechanical Engineering National University of Singapore9 Engineering Drive 1Singapore 117575Singapore Laboratory for Microstructures Shanghai UniversityShanghai 200444China

Recent studies have indicated that precipitation-strengthened high-entropy alloys(HEAs)show superior mechanical performance and have been successfully fabricated by additive ***,the lack of fatigue and fracture research has limited the engineering applications of additive manufacturing *** work explored a dual precipitation-strengthened(FeCoNi)_(86)Al_(7)Ti_(7) HEA with excellent tensile and fatigue strength,prepared through selective laser melting and heat *** with the as-built samples,the tensile properties and fatigue endurance limit improved through aging by 48.7%and 30%,*** strengthening mechanism and enhanced fatigue performance were clarified in *** improvement in fatigue strength was attributed to the improved resistance of the L1_(2) and L2_(1) *** deformation,the dislocation shear coherent L1_(2) precipitates reduced slip band energy and inhibited slip band expansion,while the L2_(1) particles acted as obstructions for further slip band propagation,severely limiting the rapid formation and propagation of crack ***-situ TEM cyclic tensile-tensile testing also clarified the fatigue crack growth behavior,demonstrating that crack deflection due to L2_(1) precipitate obstruction slowed down the crack growth rate and efficiently promoted the closure of the microcrack *** work offers im plications for a new strategy to develop additive manufacturing HEAs.

关键词： High-entropy alloy Selective laser melting Precipitation strengthening Fatigue Crack deflection

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Abnormal mechanochemical effect in ultraprecision machining of an additively manufactured precipitation-strengthened high-entropy alloy

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Journal of Materials Science & Technology 2024年第3期170卷 221-237页

作者： Long Xu Yuchao Bai Yunfa Guo Chang Ren Xiaohua Tan yandong jia Gang Wang Hao Wang Institute of Materials Shanghai UniversityShanghai 200444China Zhejiang Institute of Advanced Materials Shanghai UniversityJiashan 314100China Department of Mechanical Engineering National University of SingaporeSingapore 117575Singapore

Recently,researchers have explored the use of precipitation strengthening and finer microstructures with high-density dislocations in additive manufacturing to produce high-entropy alloys(HEAs)with adjustable ***,the inherent surface roughness and lack of machinability research in AMed HEAs limit their engineering *** this study,we systematically investigated the microstructural characteristics,mechanical properties,and machinability of Fe_(29.3)Co_(28.7)Ni_(28.6)Al_(6.8)Ti_(6.6)(at.%)HEAs with three different structures:single FCC phase cellular(SPC),dual precipitation-strengthened(DPS),and single precipitation-strengthened(SPS).These structures were fabricated by selective laser melting and isothermally annealing at 780 and 940℃.Compared to SPC HEA,DPS HEA exhibits a significant increase in yield strength and ultimate tensile strength but with a dramatic sacrifice in *** HEA exhibits similar mechanical properties to SPC HEA due to the pronounced coarsening of L21 *** ultraprecision machining micro-cutting test showed that SPC HEA had a significant mechanochem-ical effect,as evidenced by a sharp drop in cutting force for inked workpieces,but not DPS *** abnormal finding was that the negligible reflection of cutting force for SPS HEAs suggested a negative mechanochemical effect,even though SPS HEA had equally excellent plasticity like SPC *** was found that nanocrystallization-induced strength enhancement and ductility reduction of SPS HEA lead to chips’deformation dominated by shear avalanche rather than chip folding of SPC HEA,which involves the reduction of surface energy and friction of chips’***,these results and our research findings may guide the machining of AMed precipitation-strengthened HEAs and accelerate their engineering ap-plication.

关键词： High-entropy alloy Selective laser melting Precipitation strengthening Machinability Mechanochemical effect

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Simultaneously healing cracks and strengthening additively manufactured Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3) high-entropy alloy by utilizing Fe-based metallic glasses as a glue

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Journal of Materials Science & Technology 2024年第12期179卷 125-137页

作者： Hao Kang Kaikai Song Leilei Li Xiaoming Liu yandong jia Gang Wang Yaocen Wang Si Lan Xin Lin Lai-Chang Zhang Chongde Cao School of Physical Science and Technology Northwestern Polytechnical UniversityXian 710072China School of Mechanical Electrical&Information EngineeringShandong UniversityWeihai 264209China Institute of Materials Shanghai UniversityShanghai 200444China Herbert Gleiter Institute of Nanoscience School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing 210094China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXian 710072China Centre for Advanced Materials and Manufacturing School of EngineeringEdith Cowan University270 Joondalup DriveJoondalupPerthWestern Australia 6027Australia Research and Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China

Solidification cracking issues during additive manufacturing(AM)severely prevent the rapid development and broad application of this *** this work,a representative Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3) high-entropy al-loy(HEA)susceptible to crack formation was fabricated by selective laser melting(SLM).As expected,many macroscopic cracks *** crack issues were successfully solved after introducing a certain amount of Fe-based metallic glass(MG)powder as a glue during *** effect of MG addition on the formation and distribution of defects in the SLM-processed HEA was quantitatively *** an increasing mass fraction of the MG,the dominant defects transformed from cracks to lack of fusion(LOF)defects and finally ***,the MG preferred to be segregated to the boundaries of the molten ***,the coarse columnar crystals gradually transformed into equiaxed crystals in the molten pool and fine-equiaxed crystals at the edge of the molten pool,inhibiting the initiation of cracks and providing extra grain boundary ***,multiple precipitates are formed at the boundaries of cellular structures,which contribute significantly to *** to the brit-tle SLM-processed Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3) HEA,the SLM-processed HEA composite exhibited a high ultimate tensile strength greater than 1.4 Ga and enhanced *** work demonstrates that adding Fe-based MG powders as glues into SLM-processed HEAs may be an attractive method to heal cracks and simultaneously enhance the mechanical properties of additively manufactured products.

关键词： Selective laser melting High-entropy alloys Crack healing Metallic glasses Mechanical properties

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Optimization of mechanical properties of Sn-3.8Ag-0.7Cu alloys by the additions of Bi, In and Ti

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Progress in Natural Science:Materials International 2022年第5期32卷 643-654页

作者： Youyang Chen Kangdong You Shuting Yu Tixin Yang Ziqiang Dong Jincang Zhang yandong jia Gang Wang Jubo Peng Shanshan Cai Xiaobin Luo jiajun Wang Chen Liu Institute of Materials Shanghai University Materials Genome Institute Shanghai University Yunnan Tin Group (Holding) Co.Ltd.

Bi, In and Ti were added to Sn-3.8Ag-0.7Cu(SAC387) solder alloy to optimize the mechanical performance. The alloying effects of Bi, In and Ti on the microstructure, thermal and mechanical properties of SAC387 based solder alloys were investigated. The results demonstrate that adding 3.5 wt % of Bi could refine the microstructure,optimize the thermal properties, and improve the tensile strength. Meanwhile, the ductility of the solder alloys reduced evidently. Adding 2.8 wt % of In into SAC387–3.5 wt %Bi alloy could increase both the strength and ductility, which is attributed to the beneficial effect of In addition, as adding In could improve the solubility of Bi in the β-Sn matrix. Meanwhile, the melting point was reduced, and the wettability improved with the addition of In. Introducing amounts of Ti into SAC387–3.5 wt % Bi-2.8 wt % In alloy could further increase the ***, the ductility was significantly reduced when 0.8 wt % of Ti was added due to the formation of the coarse Ti2Sn3phase. The undercooling was remarkably reduced with the addition of Ti. The nanoindentation tests demonstrate that the hardness increased mainly due to the hardening effect of the Bi addition. Among all the samples prepared, alloy SAC387–3.5 wt % Bi exhibited the highest creep resistance at the ambient *** adding In and Ti into SAC387–3.5 wt % Bi alloys reduced the creep resistance of the solder alloys. The mechanism associated with the different mechanical responses is also discussed in this study.

关键词： Sn–Ag–Cu solder Alloys Microstructure Tensile strength Nanoindentation

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Design of Vehicle License Plate Positioning System Based on FPGA

Design of Vehicle License Plate Positioning System Based on ...

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第37届中国控制会议

作者： yandong jia Chunyang Wang Jilin Province Advanced Control Technology and Intelligent Automation Equipment Research Engineering Lab Changchun University of Science and Technology

Traditional License Plate Positioning（LPP） systems always utilize complex structures, resulting in low processing speed. In this paper, we propose an identification system for vehicle license plates based on Field-Programmable Gate Array（FPGA）. The improved Sobel edge detection algorithm is applied to conduct image preprocessing, and the watershed algorithm is used to identify the plates. This leads to a simplified system structure and a higher speed for the plates identification. This system uses a camera to collect image information, the FPGA to conduct image reception and processing, and a monitor to display the identification results. After debugging and executing, the design is proved to be of high performance, and is capable of applying to practical engineering projects.

关键词： License Plate Positioning Field-Programmable Gate Array image preprocessing

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Multi-Channel High Precision Time Digital Converter System Based on Equivalent Pulse Counting

Multi-Channel High Precision Time Digital Converter System B...

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第30届中国控制与决策会议

作者： yandong jia Chunyang Wang Hongwei Shi Xuelian Liu School of Electronic and Information Engineering Changchun University of Science and Technology

Time-to-digital converter（TDC） implemented in Field Programmable Gate Array（FPGA） has been developed for years and obtained superior performance. In an application with a large amount of channels, trade-off must be weighed between performance and complexity if TDC is implemented in FPGA. In this paper, a TDC prototype with equivalent pulse counting structure implemented in low-cost FPGA is presented. It contains 64 time measurement channels and can be applied in laser three–dimensional（3 D） imaging systems. Preliminary tests show the resolution after calibration can reach 72.1 ps and the standard deviation can reach 0.501 LSB.

关键词： TDC FPGA Equivalent Pulse Counting Multi-channel time measurement

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Design of Linear Active Disturbance Rejection Controller for Airborne Optical Electro Tracking Platform

Design of Linear Active Disturbance Rejection Controller for...

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第30届中国控制与决策会议

作者： Wang Chunyang Peng Yeguang Shi Hongwei jia yandong Liu Xu Academy of Electric Information Engineering Changchun University of Science and Technology

This paper introduces the architecture of two-axis and two-framework airborne optical electro tracking platform（OETP）, describes the structure and control loops. In order to eliminate the disturbances and increase the system response seed, developed a linear active disturbance rejection controller（LADRC）. Compared with PID controller under same bandwidth. The simulation results indicated that LADRC controller can makes OETP get higher performance than traditional PID controller.

关键词： automatic control technology Optical electro tracking platform linear active disturbance rejection controller

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中国潜在产出的综合测算及其政策含义

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金融研究 2019年第3期 1-17页

作者：徐忠贾彦东中国人民银行研究局北京100800

本文分别利用生产函数法、状态空间模型、宏观计量经济模型及DSGE模型四种方法,对我国1993-2018年的潜在产出进行了估算,详细分析了其变动原因和政策含义,并给出未来10年的趋势预测。主要结论有:(1) 1993-2018年我国潜在产出呈现出逐步... 详细信息

本文分别利用生产函数法、状态空间模型、宏观计量经济模型及DSGE模型四种方法,对我国1993-2018年的潜在产出进行了估算,详细分析了其变动原因和政策含义,并给出未来10年的趋势预测。主要结论有:(1) 1993-2018年我国潜在产出呈现出逐步放缓走势,平均增长率为9. 4%,略低于9. 5%的实际GDP平均增长率。其中,全要素生产率趋势平均增速为3. 6%,资本投入平均增速为11. 7%,劳动力投入平均增速为0. 6%,对潜在产出增速的平均贡献率分别为38. 3%、58. 3%和3. 4%。(2)近年来潜在产出增速的趋势性放缓主要源于高投资并未形成有效资本,进而导致有效资本投入对潜在产出的拉动力持续走低。而投资专有技术进步放缓,投资调整成本上升,资本形成效率快速下降,是有效资本投入不足和潜在产出放缓的深层次原因。这也是供给侧结构性改革的理论基础。(3)劳动力市场搜寻成本较高,供需结构不匹配,导致劳动的增长贡献率较低,我国的人口优势并未得到充分利用和有效发挥,进一步加剧了近年来潜在产出增速的趋势性放缓。(4)如果不推动供给侧结构性改革,未来5-10年我国潜在产出平均增速仍将缓慢下降。与发达经济体相比,我国潜在产出增长仍有较大提升空间,尤其在劳动投入方面。(5)政策上,应在平衡好短期需求与中长期改革目标基础上,以结构性改革为导向,完善劳动力市场,提高劳动力质量,降低就业主体的搜寻成本。着力促进全要素生产率提升,更加注重优化投资质量和结构,提高投资专有技术进步水平。

关键词：潜在产出全要素生产率投资专有技术进步资本形成效率 DSGE

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货币政策和宏观审慎政策的关联及启示——基于英格兰银行的经验

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金融研究 2019年第12期 38-57页

作者：王信贾彦东中国人民银行研究局北京100800

时至今日,宏观审慎政策在内涵、工具和框架等方面快速发展,不仅政策目标更加清晰,工具类型更加丰富,相关理论基础也在不断完善。作为危机后形成的新政策框架,宏观审慎政策在工具有效性、作用机制、政策框架设计及与货币政策的关系方面... 详细信息

时至今日,宏观审慎政策在内涵、工具和框架等方面快速发展,不仅政策目标更加清晰,工具类型更加丰富,相关理论基础也在不断完善。作为危机后形成的新政策框架,宏观审慎政策在工具有效性、作用机制、政策框架设计及与货币政策的关系方面都还有待深入研究。特别是在制度框架中,如何考虑宏观审慎政策与货币政策的关联,合理设计政策决策框架均已成为关键。对中国而言,系统风险识别、监测与分析更加复杂、困难,需要对宏观审慎政策开展更加精细、深入研究,尤其应吸收借鉴国际经验,建立、完善适合中国的宏观审慎政策框架。基于此,本文首先对宏观审慎政策的理论基础、政策目标及工具等进行系统综述,而后从两类政策关联中涉及的三个重要问题出发,着重分析宏观审慎政策与货币政策之间关系,并分别从组织架构设计、货币政策框架改革、金融政策框架设计等方面,系统介绍了英格兰银行在货币政策和宏观审慎政策框架改革的经验,重点阐述英格兰银行如何实现理论发展与制度设计的较好融合。最后,给出我国宏观审慎政策发展的若干启示和政策建议。

关键词：宏观审慎政策货币政策外部性英格兰银行

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