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Effects of post-weld Heat Treatment on Microstructure, Mechanical Properties and the Role of weld Reinforcement in 2219 Aluminum Alloy TIG-welded Joints

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Acta Metallurgica Sinica(English Letters) 2019年第6期32卷 684-694页

作者： Deng-Kui Zhang Guo-Qing Wang Ai-Ping Wu Ji-Guo Shan Yue Zhao Tian-Yi Zhao Dan-Yang Meng Jian-Ling Song Zhong-Ping Zhang Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China China Academy of Launch Vehicle Technology Beijing 100076China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationTsinghua UniversityBeijing 100084China Tianjin Long March Launch Vehicle Manufacturing Co. Ltd.Tianjin 300462China

In as-welded state,each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second *** the post-weld heat treatment,both the amount and the size of the eutectic structure orθphases ***,both the Cu content inα-Al matrix and the microhardness increased to a similar level in each region of the joint,and the tensile strength of the entire joint was greatly ***-weld heat treatment played the role of solid solution strengthening and aging *** the post-weld heat treatment,the weld performance became similar to other regions,but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff *** joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties,and the specimens randomly crack in the weld zone.

关键词： 2219 Aluminum alloy Tungsten inert gas arc welding post-weld heat treatment weld reinforcement Digital image correlation technique

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Effect of post-weld Tempering on the Microstructure and Mechanical Properties in the Simulated HAZs of a High-Strength-High-Toughness Combination Marine Engineering Steel

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Acta Metallurgica Sinica(English Letters) 2020年第3期33卷 391-402页

作者： Wen-Chao Dong Ming-Yue Wen Hui-Yong Pang Shan-Ping Lu Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Wuyang Iron and Steel Co.Ltd. Pingdingshan 462500China

The effects of tempering temperatures on the microstructure and mechanical properties of the simulated coarse-grain heataffected zone(CGHAZ) and inter-critical heat-affected zone(ICHAZ) were investigated for a high-strength-high-toughness combination marine engineering *** results demonstrate that the microstructure of the simulated CGHAZ and ICHAZ after tempering is characterized by tempering sorbites and coarse grain in the simulated *** tempering temperature increases,the tensile strength of the simulated CGHAZ and ICHAZ decreases and the Charpy absorbed energy of the simulated ICHAZ at-50℃increases remarkably,but the impact toughness of the simulated CGHAZ is not *** tempering at 550℃,the coarse flake carbides,which distribute at the prior austenite grain and martensite lath boundaries,deteriorate the impact toughness of the simulated *** the increase in tempering temperature,the morphology and the size of the carbides gradually change from coarse flake to fine granular,which is beneficial to the improvement of impact ***,the coarse-grain size of the simulated CGHAZ and the M23 C6-type carbide precipitated along the grain boundaries weakens the enhancing effect of carbides on impact toughness.

关键词： High-strength-high-toughness combination steel post-weld heat treatment Heat-affected zones(HAZs) Carbides Impact toughness

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In-situ evaluation for corrosion process at fusion boundary of stainless steel strip overlay joints in H2S containing solution

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中国有色金属学会会刊：英文版 2004年第z1期14卷 413-419页

作者： ZOU Yang PAN Chun-xu FU Qiang Department of Physics & Center for Electron Microscopy Wuhan University Wuhan 430063 China Department of Physics & Center for Electron Microscopy Wuhan University Wuhan 430063 China Department of Physics & Center for Nano-Science and Technology Wuhan University Wuhan 430063 China

The present work studied the corrosion properties around the fusion boundaries of 2.25Cr-1Mo steel with stainless steel strip overlay joints under as welded condition and after post-weld heat treatment (PWHT) in H2 S containing solution (NACE TM-01-77 standard) with different time. An in-situ observation method was introduced for evaluating corrosive progress in the fusion boundary in H2 S containing solution, that is, the samples were marked firstly at the boundary and then treated in the solution for variant time. Each time after the corrosion treatment, the observations were kept to focus at the same marked area by using scanning electron microscopy (SEM) to observe the corrosion progress. The results reveal that the fusion boundary is the worst region for corrosion resistance when comparing with other boundaries, and a broad fusion boundary has a stronger resistance for "hydrogen induced disbonding" than a narrow one.

关键词： dissimilar steel welding fusion boundary H2S corrosion post-weld heat treatment

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Residual Stress Consideration in Fatigue Damage of Offshore Wind Turbine Monopiles: To Be or Not to Be?

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World Journal of Mechanics 2020年第4期10卷 39-52页

作者： Adelani A. Oyeniran Duabari S. Aziaka Department of Advanced Mechanical Engineering Cranfield University Bedfordshire UK Centre for Propulsion Engineering Cranfield University Bedfordshire UK

The purpose of this paper was to investigate the impact of residual stresses on fatigue damage of offshore wind turbine monopiles by numerical analysis approach using ABAQUS software, a finite element analysis (FEA) tool. Three monopile models with the same dimension (within standard range) have been developed in ABAQUS and partitioned circumferentially into equal rings. Longitudinal partitions have been rotated through 180°as obtainable in practice. Characteristic loads typical of a real life offshore wind turbine environment have been applied to all three models, with tensile and compressive residual stresses applied as additional loads at the critical weld region to the first and second models while the third model had no additional load. With zero boundary conditions applied in all six degrees of freedom, the simulation has been run for 107 cycles of wind and wave loads as recommended in standards in each case. Stress results obtained from the critical weld region in the three models showed that the presence of tensile residual stresses equal to the material yield stress contributed a maximum 0.05% to fatigue damage of the monopile when compared with results from the model with no residual stress while the presence of compressive residual stresses with the magnitude of the yield stress of the material caused a gain of 0.06% in fatigue life by similar comparison, indicating negligible contribution of residual stresses to the stress build up in the critical weld region, thus suggesting that the magnitude of the residual stress as high as the yield stress of the material of the monopile is not large enough to cause the monopile to open up in the axial direction.

关键词： Concentrated Force Characteristic Loads post-weld Heat Treatment S-N Curve Superposition

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Effects of Microstructural Modification Using Friction Stir Processing on Fatigue Strength of Butt-welded Joints for High-Strength Steels

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Materials Sciences and Applications 2018年第7期9卷 625-636页

作者： Hajime Yamamoto Kazuhiro Ito Joining and welding Research Institute Osaka University Osaka Japan

Friction stir processing (FSP) is an effective surface-microstructure modification technique using a rotational tool to refine and homogenize microstructure of metallic materials. In this study, FSP was conducted on the surface of the heat-affected zone (HAZ), which is a region exhibiting degraded mechanical properties and shown to have microstructural changes, of butt-welded joints for two high-strength steels with tensile strength grades of 490 MPa and 780 MPa (hereafter HT490 and HT780, respectively). Inhomogeneous mixing of materials derived from weld metals and base metals (BMs) in a stir zone (SZ) produced inhomogeneous distribution of elements and microstructure depending on the set of the advancing side and retreating side in the SZs. The welded joints with FSP for HT490 exhibited higher hardness than that of the BM through whole of the SZ surface (fine polygonal ferrite grains and bainite structure with laths at the Mn-rich and Mn-poor regions, respectively). On the other hand, those for HT780 exhibited the minimum hardness value similar to that of the BM at the SZ surface (a few polygonal ferrite grains in the matrix of martensite laths). Fatigue strength increased by about 35 MPa and 15 MPa in stress amplitude at 107 cycles as fatigue limit due to FSP. Fatigue failure occurred at the BM and the SZ, respectively, in the welded joints modified by FSP for HT490 and HT780, in comparison with the HAZs in the as-welded joints for both grade steels. The difference in fatigue strength increase due to FSP and failure location between the welded joints for HT490 and HT780 can be attributed to the topmost SZ microstructures and their distribution.

关键词： Friction Stir Processing (FSP) High-Strength Steel Fatigue Strength Grain Refinement post-weld Treatment

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