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学者姓名：张建勋
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Abstract ：
The fracture toughness of each micro-region in 30Cr2Ni4MoV steam turbine rotor welded joint was studied, including the central zone of the SAW bead (SAW-C), the overlapping zone of the SAW bead (SAW-Z), and the central zone of the TIG weld metal (TIG), coarse-grained heating affected zone (CGHAZ), fine-grained HAZ (FGHAZ) and base metal (BM). The microstructure, fracture morphologies and cracking paths were observed by OM and SEM microscope, and the influence of microstructure on fracture toughness was analyzed. The research results show that the fracture toughness of the weld metal is lower than that of BM and HAZ, and the fracture toughness of the weld metal is non-uniform. TIG and SAW-C are composed of columnar tempered bainite, intergranular tempered lath martensite and carbides, and the fracture toughness is the worst. SAW-Z is zigzag columnar tempered bainite and equiaxed granular tempered bainite between weld passes, which has good fracture toughness. CGHAZ and FGHAZ are equiaxed tempered martensite with the best fracture toughness. By observing the fracture morphology and cracking path, SAW-C and TIG are dominated by brittle cleavage fracture mode, and SAW-Z, FGHAZ, CGHAZ and BM are in the ductile fracture mode. The straight columnar grains of SAW-C and TIG are prone to crack propagation, but the tempered bainite acts as a bridge. SAW-Z has a zigzag tempered bainite grains, and the crack propagation path is tortuous. For FGHAZ, CGHAZ and BM with equiaxed grains, the fracture toughness is related to the grain size and the dimple size around the crack tip. The crack propagation process is that the dimples are first formed in a certain range around the crack tip, but only the dimples in the lower strength micro-regions grow and merge preferentially, and rapidly form new cracks.
Keyword ：
Crack propagation Fracture toughness Micro-region Microstructure Welded rotor
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| GB/T 7714 | Guo, Yang , Li, Zeyu , Dong, Zhiwei et al. Influence of microstructure on the micro-region fracture toughness of the 30Cr2Ni4MoV turbine rotor welded joint [J]. | INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING , 2023 , 201 . |
| MLA | Guo, Yang et al. "Influence of microstructure on the micro-region fracture toughness of the 30Cr2Ni4MoV turbine rotor welded joint" . | INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING 201 (2023) . |
| APA | Guo, Yang , Li, Zeyu , Dong, Zhiwei , Xiong, Jiankun , Xu, Jian , Xu, Dexing et al. Influence of microstructure on the micro-region fracture toughness of the 30Cr2Ni4MoV turbine rotor welded joint . | INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING , 2023 , 201 . |
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Abstract ：
A novel martensitic steel powder was employed to remanufacture broken teeth on open gears by plasma arc direct energy deposition technique. To fabricate tapered rectangles resembling broken gear teeth, a process was developed and both cross sections and longitudinal sections were optimized. The hardness of the remanufactured tooth was 2.92 times that of the AISI 1045 gear, and the wear loss was decreased by 35.9%. The microstructure of the intragranular martensitic structure, the intergranular eutectic (Fe, Cr)23C6 particles and the M2B hard phase were the main reasons for the high hardness and wear resistance. The hardness of the remanufactured tooth presented a uniform distribution in general, which was due to the microstructure of the novel 1Cr17Ni2B deposition material. © 2021
Keyword ：
3D printers Chromium alloys Deposition Gear teeth Hardness Martensitic stainless steel Powder metals Textures Wear of materials Wear resistance
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| GB/T 7714 | Liu, Yan , Zhang, Jianxun , You, Qishen et al. A novel martensitic steel powder for plasma arc direct energy deposition to remanufacture broken gear teeth [J]. | Materials Letters , 2021 , 301 . |
| MLA | Liu, Yan et al. "A novel martensitic steel powder for plasma arc direct energy deposition to remanufacture broken gear teeth" . | Materials Letters 301 (2021) . |
| APA | Liu, Yan , Zhang, Jianxun , You, Qishen , Zhang, Linjie . A novel martensitic steel powder for plasma arc direct energy deposition to remanufacture broken gear teeth . | Materials Letters , 2021 , 301 . |
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Abstract ：
The EQ70 high-strength low-alloy steel plate was treated using ultrasonic impact treatment (UIT) with titanium alloy (Ti6Al4V) pins. Scanning electron microscopy with energy dispersive X-ray microanalysis and X-ray photoelectron spectroscopy were employed to study the structure, morphology, surface chemical state, and composition of the treated product on the surface of the EQ70 steel. The microhardness was measured on the surface and the cross-section of the specimens. And the electrochemical corrosion test in the 3.5 wt% NaCl medium was carried out to evaluate the corrosion resistance of the UIT-treated specimens with different impact intensities and that without UIT. It is found that the UIT with Ti6Al4V pins can result in a mixed oxide cladding layer on the surface of the steel plate, the thickness of which increased with the impact intensity (treatment time). The elements in the cladding layer mainly come from the impact pin (Ti, Al, V), base metal (Fe), and the atmosphere (0), and the contents of these elements do not change significantly with the impact intensity. TiO, TiO2, FeO and Fe2O3 are found to be the main oxides in the cladding layer. The mutual effect of the material transfer between the pin and the treated base metal is found. The surface hardness of the cladding layer increases with the impact intensity, reaching an almost constant value (approximately twice the hardness of the parent material) when the impact intensity is over 1.33 s/mm(2). The cladding layer can improve the corrosion-resistant properties of the EQ70 steel and get the best corrosion-resistant properties with an impact intensity ranging from 1.00 to 1.33 s/mm(2). The possible formation procedure of the cladding layer after UIT with titanium alloy pins is suggested. The chip from the pin (material transfer from the pin) and the mechanochemical oxidation is the main cause to form the cladding layer.
Keyword ：
Cladding layer Material transfer Oxidation Titanium alloy impact pin Ultrasonic impact treatment
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| GB/T 7714 | Liu, Chuan , Wang, Jianfei , Tian, Lihui et al. Properties and formation mechanism of cladding layer on high-strength low-alloy steel subjected to ultrasonic impact treatment with titanium alloy pin [J]. | SURFACE & COATINGS TECHNOLOGY , 2021 , 418 . |
| MLA | Liu, Chuan et al. "Properties and formation mechanism of cladding layer on high-strength low-alloy steel subjected to ultrasonic impact treatment with titanium alloy pin" . | SURFACE & COATINGS TECHNOLOGY 418 (2021) . |
| APA | Liu, Chuan , Wang, Jianfei , Tian, Lihui , Liu, Zhenguang , Wang, Jianxin , Zhang, Jianxun . Properties and formation mechanism of cladding layer on high-strength low-alloy steel subjected to ultrasonic impact treatment with titanium alloy pin . | SURFACE & COATINGS TECHNOLOGY , 2021 , 418 . |
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Abstract ：
In this article, the microstructure, micro-hardness and low-cycle fatigue property of a 12Cr/30Cr2Ni4MoV welded joint have been studied. The results show that the microstructure of the 12Cr is lath tempered martensite, 30Cr2Ni4MoV is lath tempered martensite and granular tempered bainite. The microstructure of the buttering layer (BL) and weld metal (WM) is granular tempered bainite. WM is composed of columnar grain regions and equiaxed grain regions alternately. 30Cr2Ni4MoV has higher micro-hardness than 12Cr, and the BL is the lowest. Micro-hardness in the heat-affected zone (HAZ) is gradient change. 12Cr, 30Cr2Ni4MoV and BL show cyclic softening characteristics, while WM has initial cycle hardening and subsequent cyclic softening characteristics. BL has the highest fatigue transition life; the 12Cr/BL interface is the weakest link of the low-cycle fatigue of the entire heterogeneous welded joint. The second phase particles distributed in the grain boundary or sub-grain boundary of the columnar grains have uncoordinated deformation with the matrix of WM, which result in the initiation of fatigue cracks in second phase Copyright © 2021 Transactions of the China Welding Institution. All rights reserved.
Keyword ：
Bainite Chromium alloys Fatigue of materials Grain boundaries Heat affected zone Martensite Microhardness Textures Welding
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| GB/T 7714 | Xiong, Jiankun , Shang, Chunqiang , Wu, Haifeng et al. Study on low-cycle fatigue property of 12Cr/30Cr2Ni4MoV heterogeneous joint [J]. | Transactions of the China Welding Institution , 2021 , 42 (2) : 16-23 . |
| MLA | Xiong, Jiankun et al. "Study on low-cycle fatigue property of 12Cr/30Cr2Ni4MoV heterogeneous joint" . | Transactions of the China Welding Institution 42 . 2 (2021) : 16-23 . |
| APA | Xiong, Jiankun , Shang, Chunqiang , Wu, Haifeng , Wang, Wenke , Cao, Tainlan , Zhang, Jianxun . Study on low-cycle fatigue property of 12Cr/30Cr2Ni4MoV heterogeneous joint . | Transactions of the China Welding Institution , 2021 , 42 (2) , 16-23 . |
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Abstract ：
The low-cycle fatigue (LCF) properties of Ti6Al4V and laser-welded joints with different welding speeds are studied using smooth and notched flat specimens. A local strain approach is proposed to estimate the LCF properties of the notched flat specimen based on elastic-plastic finite element analysis (EPFEA). The local strain used in the approach is defined as the average strain in the plastic zone at the notch root and critical section of the notched flat specimen. The results indicate that the local strain approach is suitable for estimating the LCF properties of the notched flat Ti6Al4V titanium alloy specimen. The stress-strain relationship derived from the microhardness can be used in the EPFEA. The LCF properties of the Ti6Al4V laser-welded joints are worse in the heat-affected zone (HAZ) than in the base metal (BM) due to the martensite structure in the HAZ and the mechanical heterogeneity in the welded joints. The LCF properties of the Ti6Al4V laser-welded joints with different welding speeds are close under low strain levels and worse with higher welding speeds under high strain levels.
Keyword ：
EPFEA laser welding LCF local strain approach Ti6Al4V titanium alloy
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| GB/T 7714 | Xu, Zhenzhen , Zhang, Jianxun , Wang, Wenke et al. Low-Cycle Fatigue Properties of Ti6Al4V Laser-Welded Joints Based on a Local Strain Approach [J]. | JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE , 2021 , 30 (4) : 2772-2780 . |
| MLA | Xu, Zhenzhen et al. "Low-Cycle Fatigue Properties of Ti6Al4V Laser-Welded Joints Based on a Local Strain Approach" . | JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE 30 . 4 (2021) : 2772-2780 . |
| APA | Xu, Zhenzhen , Zhang, Jianxun , Wang, Wenke , Sun, Pinpin . Low-Cycle Fatigue Properties of Ti6Al4V Laser-Welded Joints Based on a Local Strain Approach . | JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE , 2021 , 30 (4) , 2772-2780 . |
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Abstract ：
The dissimilar rotor steel welded joint (12Cr/30Cr2Ni4MoV) with buttering layer is fabricated by using the combined welding technology of narrow-gap tungsten inert gas (NG-TIG) and narrow-gap submerged arc welding (NG-SAW). The shear strength of joint microzone is obtained by microshear test, and the ductile-brittle transition temperature FATT50 of microzones is obtained by partition test. The influence of microstructure on hardness, strength and toughness of microzones is investigated. The results indicate that the distribution characteristics of hardness and shear strength in welded joint are basically the same. The mechanical properties of HAZs exhibit gradient distribution, and interface mechanical properties mismatch on both sides of the fusion line. There is a local weakening area in buttering layer, and the micro-hardness value is 227 HV, which is the weakest area of the whole welded joint. From base metal 12Cr to 30Cr2Ni4MoV, the ductile-brittle transition temperature FATT50 of joint microzones gradually decreases. At 20, the impact toughness of 30Cr2Ni4MoV and its heat affected zone is excellent, with generation of cracks at the interface between matrix and second phase, ductile fracture occurs through the aggregation of micropores. Quasi-cleavage fracture occurs in all the other microrzones, and the impact toughness of welded metal is the weakest. © 2021 Journal of Mechanical Engineering.
Keyword ：
Chromium alloys Chromium steel Ductile fracture Fracture toughness Gas welding Heat affected zone Inert gases Microhardness Molybdenum steel Nickel steel Submerged arc welding Temperature Vanadium steel Welded steel structures
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| GB/T 7714 | Zhu, Bo , Wang, Wenke , Guo, Yang et al. Research on Impact Toughness in Microzones of 12Cr/30Cr2Ni4MoV Dissimilar Rotor Steel Welded Joint [J]. | Journal of Mechanical Engineering , 2021 , 57 (2) : 53-61 . |
| MLA | Zhu, Bo et al. "Research on Impact Toughness in Microzones of 12Cr/30Cr2Ni4MoV Dissimilar Rotor Steel Welded Joint" . | Journal of Mechanical Engineering 57 . 2 (2021) : 53-61 . |
| APA | Zhu, Bo , Wang, Wenke , Guo, Yang , Xiong, Jiankun , Zhang, Jianxun . Research on Impact Toughness in Microzones of 12Cr/30Cr2Ni4MoV Dissimilar Rotor Steel Welded Joint . | Journal of Mechanical Engineering , 2021 , 57 (2) , 53-61 . |
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Abstract ：
Buttering layer (BL) was used to weld two ultra-supercritical turbine rotor steels. Low-cycle fatigue behavior of different regions in the dissimilar metal welded joint (DMWJ) was compared and evaluated at 280 °C. Microstructure, fracture and weak link were observed by OM, SEM, EDS and TEM. BL had lower fatigue life than weld metal (WM) and base metals (BMs). Weld zone showed cyclic softening characteristic. Microstructures evolved into cell structures after LCF tests. Fatigue crack in weld zone propagated mainly through coarse carbides. The interface near BL was the weakest link of the DMWJ due to ferrite layer and strength mismatch. © 2020 Elsevier Ltd
Keyword ：
Carbides Fatigue of materials Microstructure Turbine components Welding Welds
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| GB/T 7714 | Wang, Wen-Ke , Zhang, Jian-Xun , Zhong, Jie . Comparative evaluation of LCF behavior of dissimilar steels and welds in an ultra-supercritical turbine rotor at 280 [J]. | International Journal of Fatigue , 2020 , 139 . |
| MLA | Wang, Wen-Ke et al. "Comparative evaluation of LCF behavior of dissimilar steels and welds in an ultra-supercritical turbine rotor at 280" . | International Journal of Fatigue 139 (2020) . |
| APA | Wang, Wen-Ke , Zhang, Jian-Xun , Zhong, Jie . Comparative evaluation of LCF behavior of dissimilar steels and welds in an ultra-supercritical turbine rotor at 280 . | International Journal of Fatigue , 2020 , 139 . |
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Abstract ：
The microhardness curve trend and its relationships with microstructure and misorientation were analyzed to enhance the comprehension of the microstructure and mechanical property of micro-areas in Ti6Al4V laser-welded joints with different welding speeds. The microhardness measured on the fusion line (Hm) is the highest from the weld center to the base metal. Hm increases with increasing weld width in a welded joint and increasing degree of the non-uniformity in all studied welded joints. The microhardness decreases from the weld metal to the base metal with decreasing amount of martensite α’ and increasing amount of original α phase. When the microstructure is mainly composed of martensite α’, the microhardness changes with the cooling rate, grain size of the martensite, and peak values of the fraction of misorientation angle of the martensite in a wide weld metal zone or weld center at different welding speeds, whereas the difference is small in a narrow weld metal zone. © 2020 The Nonferrous Metals Society of China
Keyword ：
Aluminum alloys Martensite Metals Microhardness Microstructure Ternary alloys Titanium alloys Vanadium alloys Welding Welds
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| GB/T 7714 | XU, Zhen-zhen , DONG, Zhi-qiang , YU, Zhao-hui et al. Relationships between microhardness, microstructure, and grain orientation in laser-welded joints with different welding speeds for Ti6Al4V titanium alloy [J]. | Transactions of Nonferrous Metals Society of China (English Edition) , 2020 , 30 (5) : 1277-1289 . |
| MLA | XU, Zhen-zhen et al. "Relationships between microhardness, microstructure, and grain orientation in laser-welded joints with different welding speeds for Ti6Al4V titanium alloy" . | Transactions of Nonferrous Metals Society of China (English Edition) 30 . 5 (2020) : 1277-1289 . |
| APA | XU, Zhen-zhen , DONG, Zhi-qiang , YU, Zhao-hui , WANG, Wen-ke , ZHANG, Jian-xun . Relationships between microhardness, microstructure, and grain orientation in laser-welded joints with different welding speeds for Ti6Al4V titanium alloy . | Transactions of Nonferrous Metals Society of China (English Edition) , 2020 , 30 (5) , 1277-1289 . |
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Abstract ：
High cycle fatigue (HCF) behaviors were systematically evaluated of a CrMoV/NiCrMoV dissimilar metal welded joint (DMWJ) with buttering layer in steam turbine rotor at 280 °C. Fatigue curves and parameters of the base metals (BMs), weld metal (WM), buttering layer (BL) and heat affected zones (HAZs) in the welded joint were obtained. Characteristic microstructures, carbides, and fatigue fracture were observed using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrum (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD). The results show that the fatigue properties of each region in the DMWJ are different. Fine-grained HAZs show a lower slop of fatigue curve than BMs. The fracture locations of HAZs occur at fusion boundaries, and this is related to the ferrite layer and carbon migration at the interface. The interface with ferrite layer is the weakest zone in whole DMWJ. After fatigue, dislocation density increases, and the dislocations are mainly entangled around the carbides, which enhances the fatigue properties of the welded joint. Coarse M7C3-type carbides in BL and WM are mainly concentrated on the subgrain boundary, and this causes fatigue crack propagation along the carbides. A fatigue fracture model associated with carbide is established to explain the cause and process of the fatigue crack propagation along carbides. © 2020 Elsevier B.V.
Keyword ：
Carbides Chromium compounds Cracks Fatigue crack propagation Fatigue of materials Ferrite Fracture Heat affected zone High resolution transmission electron microscopy Scanning electron microscopy Welding
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| GB/T 7714 | Wang, Wen-Ke , Liu, Yan , Guo, Yang et al. High cycle fatigue and fracture behaviors of CrMoV/NiCrMoV dissimilar rotor welded joint at 280 °C [J]. | Materials Science and Engineering A , 2020 , 786 . |
| MLA | Wang, Wen-Ke et al. "High cycle fatigue and fracture behaviors of CrMoV/NiCrMoV dissimilar rotor welded joint at 280 °C" . | Materials Science and Engineering A 786 (2020) . |
| APA | Wang, Wen-Ke , Liu, Yan , Guo, Yang , Xu, Zhen-Zhen , Zhong, Jie , Zhang, Jian-Xun . High cycle fatigue and fracture behaviors of CrMoV/NiCrMoV dissimilar rotor welded joint at 280 °C . | Materials Science and Engineering A , 2020 , 786 . |
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Abstract ：
2 mm-thick 6061-T6 aluminum alloy and SPCC cold-rolled steel plate are used to obtain aluminum steel composite joints with both fusion and brazing characteristics by means of wire filling laser brazing method. The influences of pre-coated flux, groove bevel angle, bevel morphology and solder composition on the microstructure and mechanical properties of brazing joint are studied. The results show that pre-coating flux can greatly improve wettability of filler metal. The mechanical properties of laser brazing joint are better when 60° groove is prefabricated on the side of steel base metal than when 45° groove is prefabricated.. When the prefabricate groove angle of steel material is 60°, and the laser power, welding speed, wire feeding speed, laser defocusing amount, offset center of the laser spot center are 3.1 kW, 0.5 m/min, 2 m/min, -8 mm, +0.6 mm, respectively, with ER2319 Al-Cu filler metal, the average and maximum tensile strength of the joint are respectively 147 MPa and 159 MPa, the interface layer presents short whisker shape, the interface layer is 5-8 μm in thickness, the Cu element is dissolved in Al-Fe brittle phase by replacing Fe elements to reduce its brittleness. With ER5356 Al-Mg filler metal, the average tensile strength of the joint is 118 MPa when the laser power is 3 kW, the interface layer presents coarse saw tooth shape, and consists of FeAl2, Fe2Al5 and FeAl3 phase, the interface layer is 8-12 μm in thickness, the Mg element is gathered at the outside of brittle phase, and it has no obvious inhibitory effect on the growth of Al-Fe brittle phase; with ER4043 Al-Si filler metal, the average tensile strength of the joint is 129 MPa when the laser power is 3 kW, the interface layer presents small saw tooth shape, the interface layer is 3-4.5 μm in thickness, the Si element is dissolved in Al-Fe brittle phase to inhibit its growth. © 2020 Journal of Mechanical Engineering.
Keyword ：
Aluminum alloys Aluminum coated steel Binary alloys Brazing Cold rolled steel Cold rolling Filler metals Fillers Fracture mechanics Magnesium alloys Metal cladding Metals Morphology Silicon Steel sheet Tensile strength Welding
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| GB/T 7714 | Zhang, Jianxun , Jiang, Xu , Xu, Zhenzhen et al. Study on Characteristics of Laser Welding-brazing of 6061 Aluminum Alloy to SPCC Cold Rolled Steel [J]. | Journal of Mechanical Engineering , 2020 , 56 (6) : 41-49 . |
| MLA | Zhang, Jianxun et al. "Study on Characteristics of Laser Welding-brazing of 6061 Aluminum Alloy to SPCC Cold Rolled Steel" . | Journal of Mechanical Engineering 56 . 6 (2020) : 41-49 . |
| APA | Zhang, Jianxun , Jiang, Xu , Xu, Zhenzhen , Zhang, Guifeng . Study on Characteristics of Laser Welding-brazing of 6061 Aluminum Alloy to SPCC Cold Rolled Steel . | Journal of Mechanical Engineering , 2020 , 56 (6) , 41-49 . |
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