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Effect of Ultrasonic Impact on the Microstructure of Welded Joint of 2195 Al–Li Alloy

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Acta Metallurgica Sinica(English Letters) 2016年第4期29卷 367-372页

作者： Qi-Hao Chen san-bao lin Chun-Li Yang Cheng-Lei Fan State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology

It is known that an ultrasonic impact during tungsten inert gas welding can refine the grains and improve the mechanical properties of the welded joints of aluminum alloys. However, the influence mechanism of the ultrasonic impact on the microstructures is still unclear. In this research, the effects of the mechanical and ultrasonic impact on the microstructures of the welded joint of 2195 Al-Li alloy are analyzed. It is found that the mechanical impact could not refine the grains, but the ultrasonic impact could refine the grains. The grains become smaller in the weld center with an increase in the ultrasonic amplitude. Possible mechanisms for the grain refinement are discussed. The results show that the small temperature gradient promotes formation of the equiaxed grain and the cavitation promotes heterogeneous nucleation.

关键词： Ultrasound TIG welding Microstructure Al-Li alloy

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Defence Technology(防务技术) 2023年第9期27卷 138-153页

作者： Zeng Liu Cheng-lei Fan Chun-li Yang Zhu Ming san-bao lin Lang-ping Wang State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin150001China Inner Mongolia Metal Material Research Institute Yantai264000China

Ar-N_(2)-O_(2)ternary shielding gas is employed in dissimilar welding between high nitrogen steel and low alloy *** effect of O_(2)and N_(2)is investigated based on the systematical analysis of the metal transfer,nitrogen escape phenomenon,weld appearance,nondestructive detection,nitrogen content distribution,microstructure and mechanical *** are two nitrogen sources of the nitrogen in the weld:high nitrogen base material and shielding *** effect of shielding gas is mainly reflected in these two *** change of the droplet transfer mode affects the fusion ratio,N2in the shielding gas can increase nitrogen content and promote the nitrogen uniform *** addition of 2%O_(2)to Ar matrix can change the metal transfer from globular transfer to spray transfer,high nitrogen base material is thereby dissolved more to the molten pool,making nitrogen content increase,ferrite decrease and the mechanical properties *** applying N2-containing shielding gas,arc stability becomes poor and short-circuiting transfer frequency increases due to the nitrogen escape from droplets and the molten *** of the joints is improved with N_(2)increasing,but internal gas pores are easier to appear because of the poor capacity of low alloy steel to dissolve nitrogen,The generation of pores will greatly reduce the impact resistance.4-8%N2content in shielding gas is recommended in this study considering the integrated properties of the dissimilar welded joint.

关键词： High nitrogen steel Dissimilar steel joints Shielding gas Metal transfer Microstructure Mechanical properties

Effect of Ultrasound on Heterogeneous Nucleation in TIG Welding of Al–Li Alloy

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Acta Metallurgica Sinica(English Letters) 2016年第12期29卷 1081-1088页

作者： Qi-Hao Chen san-bao lin Chun-Li Yang Cheng-Lei Fan Hong-Liang Ge State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology

The effect of ultrasound on heterogeneous nucleation in a tungsten inert gas （TIG） weld pool of 2195 Al-Li alloy has been investigated by a series of experiments. An ultrasonic vibration was imposed on the surface of base material before turning off the welding arc during the TIG welding implemented at a fixed point. The results suggest that ultrasound could promote heterogeneous nucleation in the TIG weld pool of 2195 Al-Li alloy. The grain around the fusion zone is changed from a column grain to an equiaxed grain after applying the ultrasonic treatment. To study the influencing mechanism of ultrasound on heterogeneous nucleation, further investigations were implemented where the welding arc was turned off after turning off the ultrasonic power. The results show that the equiaxed grain around the fusion zone disappeared gradually with an increase in heat input after turning off the ultrasonic power. It suggests that ultrasound could promote the heterogeneous nucleation particle to nucleate in advance before turning off the welding arc and the crystal nucleus could again be melted with an increase in heat input after turning off the ultrasonic power. Moreover, the effects of the welding current and ultrasonic amplitude on heterogeneous nucleation in the weld pool of 2195 Al-Li alloy were also investigated. Possible influencing mechanism of the welding current and ultrasonic amplitude on heterogeneous nucleation was discussed.

关键词： Ultrasound TIG welding Grain Al-Li alloy

Microstructure and Corrosion Behavior of Friction Stir Welded Al Alloy Coated by In Situ Shot-Peening-Assisted Cold Spray

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 172-182页

作者： Hua Zhang Chang-Yu Zhao Qi-Long Guo Rui-Sheng Yang Li-Yuan Liu san-bao lin School of Mechanical Engineering Beijing Institute of Petrochemical TechnologyBeijing 102617China Beijing Institute of Astronautical Systems and Engineering Beijing 100076China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China

To improve the corrosion resistance of friction stir welded(FSW)joints,in situ shot-peening-assisted cold spray coating was applied to the surface of FSW *** microstructure and corrosion behavior of the coatings were *** results showed that a dense coating was obtained by cold spraying ***,the use of in situ shot-peeningassisted technology significantly reduced the porosity of the coating,which has a positive impact on the microstructure and the mechanical *** corrosion tests showed that the coating aff ected positively on the corrosion *** the coated surface,the craters caused by shot-peening particles were corroded in the form of exfoliation corrosion,while the exposed particles were corroded in the form of intercrystalline *** work provides a new approach to the corrosion protection of FSW joints.

关键词： Aluminum alloy coating Cold spray Friction stir welding In situ shot-peening Intergranular corrosion

Gas metal arc welding of high nitrogen stainless steel with AreN_(2)-O_(2)ternary shielding gas

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Defence Technology（防务技术） 2021年第3期17卷 923-931页

作者： Zeng Liu Cheng-lei Fan Zhu Ming Chao Chen Ang Liu Chun-li Yang san-bao lin Lang-ping Wang State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin150001China Inner Mongolia Metal Material Research Institute BaotouChina

High nitrogen stainless steel with nitrogen content of 0.75%was welded by gas metal arc welding with Ar-N_(2)-O_(2)ternary shielding *** effect of the ternary shielding gas on the retention and improvement of nitrogen content in the weld was *** test was conducted first to compare the ability of O_(2)and CO_(2)in prompting nitrogen *** nitrogen content of the surfacing metal with O_(2)is slightly higher than CO_(2).And then AreN_(2)-O_(2)shielding gas was applied to weld high nitrogen stainless *** using N_(2)-containing shielding gas,the nitrogen content of the weld was improved by 0.1 wt%.As N_(2)continued to increase,the increment of nitrogen content was not obvious,but the ferrite decreased from the top to the *** the proportion of N_(2)reached 20%,a full austenitic weld was obtained and the tensile strength was improved by 8.7%.Combined with the results of surfacing test and welding test,it is concluded that the main effect of N_(2)is to inhibit the escape of nitrogen and suppress the nitrogen diffusion from bottom to the top in the molten pool.

关键词： High nitrogen stainless steel AreN2-O2 shielding gas Action mechanism

Long-term Evolution of Solar Activity and Prediction of the Following Solar Cycles

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Research in Astronomy and Astrophysics 2024年第3期24卷 194-204页

作者： Pei-Xin Luo bao-lin Tan National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

Solar activities have a great impact on modern high-tech systems,such as human aerospace activities,satellite communication and navigation,deep space exploration,and related scientific ***,studying the long-term evolution trend of solar activity and accurately predicting the future solar cycles are highly *** on the wavelet transform and empirical function fitting of the longest recorded data of the annual average relative sunspot number(ASN)series of 323 yr to date,this work decisively verifies the existence of the solar century cycles and confirms that its length is about 104.0 yr,and the magnitude has a slightly increasing trend on the timescale of several hundred *** on this long-term evolutionary trend,we predict solar cycles 25 and26 by using phase similar prediction *** for solar cycle 25,its maximum ASN will be about146.7±33.40,obviously stronger than solar cycle *** peak year will occur approximately in 2024,and the period will be about 11±1 *** for solar cycle 26,it will start around 2030,and reach its maximum between2035 and 2036,with maximum ASN of about 133.0±3.200,and period of about 10 yr.

关键词： Sun activity-Sun evolution-(Sun) sunspots-methods data analysis

An isolated symmetrical 2T2R cell enabling high precision and high density for RRAM-based in-memory computing

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Science China(Information Sciences) 2024年第5期67卷 287-294页

作者： Yaotian linG Zongwei WANG Yuhang YANG lin bao Shengyu bao Qishen WANG Yimao CAI Ru HUANG School of Integrated Circuits Beijing Advanced Innovation Center for Integrated Circuits Peking University State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications

In-memory computing(IMC), leveraging emerging memories, holds significant promise in overcoming memory limitations and improving energy efficiency. However, the prevailing IMC array structure based on serially connected transistors and memory cells(1T1R/2T2R), along with the signed weight mapping scheme, can lead to asymmetrical weight sensing issues(AWS) due to electrical asymmetry within the1T1R/2T2R structure, particularly in highly scaled cells where the transistor's resistance becomes significant. In this paper, we propose and fabricate an electrically symmetric memory cell based on a physically isolated 2T2R structure for IMC. This design aims to enhance the precision and density of RRAM-based IMC arrays. The 2T2R cells are manufactured using the back-end-of-line(BEOL) process of a commercial40 nm technology platform. The feasibility of this design is verified through measured and simulated results,showcasing its capability to address the issue of AWS. Compared to conventional 2T2R cells, this design achieves a considerably smaller transistor footprint without compromising accuracy, while also improving integration density by 42.2%. These innovative memory cell advancements have the potential to further advance high-energy-efficient IMC technology.

关键词： RRAM 2T2R multi-level storage weight asymmetry in-memory computing

Effect of Mo and cold forging deformation on strength and ductility of cobalt-based alloy L605

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Journal of Iron and Steel Research International 2024年第7期31卷 1811-1823页

作者： Zhong-lin Wang Zhi-hua Gong Quan Li Han-sheng bao School of Materials and Metallurgy Inner Mongolia University of Science and TechnologyBaotou 014017Inner MongoliaChina Institute of Special Steels Central Iron and Steel Research Institute Co.Ltd.Beijing 100081China

Mo element was added to cobalt-based alloy L605,and cold forging deformation was *** effects of the addition and cold forging deformation on the microstructure and mechanical properties of the alloy were studied by thermodynamic calculation,electron backscatter diffraction,transmission electron microscopy,and X-ray *** stacking fault energy(SFE)of the alloy decreased after the addition,and the formation of stacking faults and intersections were promoted to improve the strength and *** tensile strength of the alloy with Mo increased from 1190 to 1702 MPa after 24%cold deformation,producing significant work *** strengthening mechanism is strain-induced martensitic transformation(SIMT)and deformation *** alloy,combined with Mo and after 24%deformation,had both high strength and ductility in comparison with the original cobalt-based alloy *** is attributed to the lower SFE which caused the increase in stacking fault *** the tensile process,theε-hcp phase was easily generated at the stacking fault to reduce the stress concentration and increase the *** SIMT by adjusting the density of stacking faults can improve the mechanical properties of cobalt-based ***ε-hcp phase,the interaction between deformation twins and dislocations,and the interaction between e-hcp phases during cold forging deformation caused local stress concentration,lowering ductility and toughness.

关键词： Cobalt-based alloy-Stacking fault energy Strain-induced martensitic transformation Deformation twin Cold forging deformation

Intelligent casting:Empowering the future foundry industry

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China Foundry 2024年第5期21卷 409-426页

作者： Jin-wu Kang bao-lin Liu Tao Jing Hou-fa Shen School of Materials Science and Engineering Key Laboratory for Advanced Materials Processing TechnologyTsinghua UniversityBeijing 100084China

Emerging technological advances are reshaping the casting sector in latest *** technology is evolving towards intelligent casting paradigm that involves automation,greenization and intelligentization,which attracts more and more attention from the academic and industry *** this paper,the main features of casting technology were briefly summarized and forecasted,and the recent developments of key technologies and the innovative efforts made in promoting intelligent casting process were ***,the technical visions of intelligent casting process were also put *** key technologies for intelligent casting process comprise 3D printing technologies,intelligent mold technologies and intelligent process control *** future,the intelligent mold that derived from mold with sensors,control devices and actuators will probably incorporate the Internet of Things,online inspection,embedded simulation,decision-making and control system,and other technologies to form intelligent cyber-physical casting system,which may pave the way to realize intelligent *** is promising that the intelligent casting process will eventually achieve the goal of real-time process optimization and full-scale control,with the defects,microstructure,performance,and service life of the fabricated castings can be accurately predicted and tailored.

关键词： intelligent casting 3D printing intelligent mold process control cyber-physical casting system embedded simulation