Microstructure and Mechanical Property of Brazed Joints in Titanium Alloy and Aluminum Alloy Combination with Tin Foil Interlayer

Xinjian Yuan,Xuebo Liang,Xiuyang Li,Miao Hong,Kunlun Tang 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Brazing of a titanium alloy and an aluminum alloy was performed in a vacuum furnace with a pure tin foil interlayer. The microstructure and mechanical property of the brazed joint were investigated as functions of parameters including post bonding heat treatment. The results indicated that Al-Ti-Sn secondary phases were present in the joining region. These secondary phases coarsened clearly with increasing temperature from 450oC to 500oC. At 450oC, the unbonded zone appeared in the interface area between the Ti alloy and the joining zone. At 500oC, some cracks and coarsened secondary phases were observed in the joint. From 450oC to 500oC, the strength of the joint gave a hill-shaped curve change. The fracture was mainly brittle fracture. As the post bonding heat treatment was applied, the interdiffusion region with about 6 μm was found in the interface zone between the Ti alloy and the joining area, the secondary phases distributed with a small and dispersed pattern, and the tensile strength of the joint was improved to a higher value. Failure mode with lots of dimples was a ductile pattern.

Gut Microbiota Alteration Influences Colorectal Cancer Metastasis to the Liver by Remodeling the Liver Immune Microenvironment

Yuan Na,Li Xiaoyan,Wang Meng,Zhang Zhilin,Qiao Lu,Gao Yamei,Xu Xinjian,Zhi Jie,Li Yang,Li Zhongxin,Jia Yitao 거트앤리버 소화기연관학회협의회 2022 Gut and Liver Vol.16 No.4

Background/Aims:This study aimed to explore the effect of gut microbiota-regulated Kupffer cells (KCs) on colorectal cancer (CRC) liver metastasis. Methods: A series of in vivo and in vitro researches were showed to demonstrate the gut microbiota and its possible mechanism in CRC liver metastasis. Results: Fewer liver metastases were identified in the ampicillin-streptomycin-colistin and colistin groups. Increased proportions of Parabacteroides goldsteinii, Bacteroides vulgatus, Bacteroides thetaiotaomicron, and Bacteroides uniformis were observed in the colistin group. The significant expansion of KCs was identified in the ampicillin-streptomycin-colistin and colistin groups. B. vulgatus levels were positively correlated with KC levels. More liver metastases were observed in the vancomycin group. An increased abundance of Parabacteroides distasonis and Proteus mirabilis and an obvious reduction of KCs were noted in the vancomycin group. P. mirabilis levels were negatively related to KC levels. The number of liver metastatic nodules was increased in the P. mirabilis group and decreased in the B. vulgatus group. The number of KCs decreased in the P. mirabilis group and increased in the B. vulgatus group. In vitro, as P. mirabilis or B. vulgatus doses increased, there was an opposite effect on KC proliferation in dose- and time-dependent manners. P. mirabilis induced CT26 cell migration by controlling KC proliferation, whereas B. vulgatus prevented this migration. Conclusions: An increased abundance of P. mirabilis and decreased amount of B. vulgatus play key roles in CRC liver metastasis, which might be related to KC reductions in the liver.

Microtubule WGM Sensor: Applications and Key Technologies

Yuan Guoqing,Li Hong,Luo Xinjian,Lu Lidan,Zhu Lianqing 한국바이오칩학회 2023 BioChip Journal Vol.17 No.2

Whispering gallery mode (WGM) microtubule resonators are widely used in highly sensitive sensing applications due to their ultra-high quality factor Q and extremely small mode size. Capillary microtubules, as sensing devices, have the advantages of low reagent sample consumption, a large specific surface area to enhance analytical sensitivity, and a fast mass transfer rate to shorten analysis time. In recent years, research scholars have conducted extensive and in-depth studies on the optimization of microtubule resonators. However, there are still several problems that limit the development of the technology applications and solutions that need to be explored. Therefore, this paper analyzes the current research status of resonant sensing technology in microtubule whispering gallery, analyzes key problems, and points out research priorities and methods in coupled resonance technology and microtubule structure optimization. Finally, suggestions for future development are made.

Effect of High Energy Shot Peening on the Microstructure and Mechanical Property of AZ31B Mg Alloy/HSLA350 Steel Lap Joints

Rui Li,Xinjian Yuan,Ting Li,Miao Hong,Shiwei Tao,Zhuo Chen,Ge Wang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.5

When using high energy shot peening (HESP) technology, the surface layer of the welded joints produced grain breakage and residual compressive stress. When the shot peening strength is the optimal parameter 0.10 MPa, the residual compressive stress reaches a maximum value of 74.02 MPa, dislocation density in welded joints increased significantly and the tensile shear strength of the joint was increased by 18.6% compared to the joint without HESP treatment (205 MPa), and the fracture position of the welded joint was located in the Al alloy base material, these were brought by fi ne grain strengthening and strain strengthening. When the shot peening strength was 0.05 MPa, the strength of the joint was also improved, but the fracture position of the joint was the same as that without HESP treatment, and they were all in the fusion zone. However, when the shot peening strength was further increased to 0.15 MPa, severe cracks appeared inside the joint, which deteriorates the strength of the Mg/steel joint.

Nugget Formation and Its Mechanism of Resistance Spot Welded Joints in DP600 Dual-Phase and DC54D Ultralow Carbon Steel

Ci Li,Xinjian Yuan,Kanglong Wu,Haodong Wang,Zhan Hu,Xueyu Pan 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.3

Resistance spot welded joints in different configurations of DP600 and DC54D were investigated to elucidate thenugget formation process and mechanical properties of the resultant joints. Results show that, when the weldingtime was less than 4 cycles, the fusion zone (FZ) was not formed, but the heat-affected zone (HAZ) occurred with a“butterfly” shape. In 4 cycles, the FZ in dissimilar sheets occurred with an “abnormal butterfly” shape because of nuggetshift. When the welding time increased to 14 cycles, the FZ exhibited a “bread loaf” shape and the weld shifted to“dog bones.” The nugget can be divided into three regions, namely, FZ, HAZ1, and HAZ2, and the FZ consisted oflath martensite. The micro hardness of DP600 FZ was lower than that of HAZ because of the dilution of DC54D. The failure mode of B changed from interfacial failure to plug failure during the nugget formation process. The tensile-shear load of sound weld is 6.375, 6.016, and 19.131 kN.

Dissimilar Resistance Spot Welding of DP 600/A5052/DP 600 Triple Sheets

Ting Li,Xinjian Yuan,Zhan Hu,Kanglong Wu,Haodong Wang,Bangqiang Zhang 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.11

Triple sheets of DP 600/A5052 aluminum alloy/DP 600 steel were joined by means of resistance spot welding in this study. The experimental results showed that the microstructure of fusion zone was lath martensite for DP 600 and column crystals for A5052. Their grains coarsened with increasing distance away from the base metals. The interface zone between DP 600 and A5052 was composed of continuous Fe2Al5 intermetallic compound (IMC) layer and needle-like Fe4Al13 IMC. When welding time prolonged from 8 cycles to 17 cycles, the average length of Fe4Al13 phase adjacent to A5052 shortened from 2.3 μm to 0.89 μm, whereas the thickness of Fe2Al5 IMC layer near DP 600 widened from 1.59 μm to 2.59 μm. The tensile-shear load of DP 600/A5052/DP 600 joints reached a maximum value of 10.796 kN with 14 cycles welding time. Failure during tensile-shear testing occurred along DP 600/A5052 interfaces because Fe2Al5 and Fe4Al13 were brittle phases, but an amount of tearing area was found on the fracture surface.

Microstructure, Mechanical Properties and Failure Mechanisms of Resistance Spot Welding Joints between Ultra High Strength Steel 22MnB5 and Galvanized Steel HSLA350

Xuebo Liang,Xinjian Yuan,Haodong Wang,Xiuyang Li,Ci Li,Xueyu Pan 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.12

Resistance spot welding of 22MnB5/HSLA350 and its weldability are investigated. From base material to the nugget, the microstructure of 22MnB5 side can be expressed as M/tempered M+ granular carbides/F+M/fine M/lath M, and on HSLA350 side, F+M/F+flocculent P+tempered M/F+flocculent P+M/F+M/lath M are observed. The heat-affected zone (HAZ) of 22MnB5 exhibits obvious softening region and strengthening region caused by the tempered M and quite fine M, respectively. The peak load of welded joints undergoes two stages of a dramatic increase and a subsequent decrease with increases in the welding current. The maximum value (13.82 kN) of peak load is achieved at a welding current of 8 kA. The failure modes involving interfacial failure (IF), pullout failure from the galvanized steel (PFG), pullout failure from boron steel and tearing of the galvanized steel (PFB-TG) and pullout failure from the boron steel (PFB) are discussed in detail.

Microstructure and Mechanical Characteristics of Dissimilar TIG Welded 9% Cr Heat-Resistant Steels Joints

Ting Li,Xinjian Yuan,Rui Li,Jiankun Xiong,Shiwei Tao,Kanglong Wu 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.6

Dissimilar 9% Cr heat-resistant steels (G115 and CB2) with good creep properties for ultra-supercritical steam turbines were butt-joined by tungsten inert gas welding. The microstructure of welded metal (WM) was quenched martensite without carbide precipitates and lath packets existed inside prior austenite grains (PAGs), which leaded to higher hardness of WM. Partially melted zone at G115 side was composed of untempered martensite within equiaxed PAGs. The lowest hardness occurred in both G115 and CB2 steels which was attributed to tempered martensite with many M 23 C 6 precipitates. The heat-affected zone consisted of three sub-grains and their microstructure was detailly analyzed in current work. As current increased from 130 to 150 A, both the tensile strength at room temperature and 650°C increased while strength had no obvious change with further increasing current. The values of 673 MPa and 309 MPa corresponded to the tensile stress with 150 A at room temperature and 650°C, respectively. The fracture mode of joints at room temperature was cleavage and ductile failure at 130 and 150 A, respectively. The high-temperature fracture surface at 150 A was composed of deep and fi ne dimples.

Formation Mechanisms for (Cr,Co)7C3/(Cr,Co)23C6 Heterogeneous Precipitates and Stacking Faults Around Carbides in Surfacing Welding of Stellite Alloy on Stainless Steel

Jiankun Xiong,Haibo Zhang,Fuheng Nie,Fen He,Jianping Yang,Zhan Hu,Zhongbo Wen,Haiyan Zhao,Xinjian Yuan 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7

The formation mechanisms for two carbides with co-existence and increasing stacking faults nearby the carbides duringsurfacing welding were investigated in this study. The results indicated that the surfacing layer had a two-phase structure ofa matrix phase and a second phase, the density of the second phase was relatively small and the second phase was discontinuous,by contrast with the as-received welding wire. Relatively uniform microstructure of surfacing layer and the weldinginterface without melting of base metal were obtained, resulting in an inapparent change in the microhardness. A few carbideswith blocky shape were identified in the surfacing layer. The mechanisms for (Cr,Co)23C6 of face-centered cubic crystalstructure co-existing with (Cr,Co)7C3 of hexagonal close-packed crystal structure and (Cr,Co)23C6 subsequently forming closeto the pre-formed (Cr,Co)7C3 during the cooling process were discussed in alloying element, calculated equilibrium phasediagram, Gibbs energy, etc. The relatively higher density of the stacking fault present around the carbides was understoodfrom forming energy of stacking faults.