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Lei Y.,Jiangsu University | Lei Y.,Jiangsu Province Key Laboratory of High End Structural Materials | Gong C.,Jiangsu University | Luo Y.,Jiangsu University | And 2 more authors.
Cailiao Yanjiu Xuebao/Chinese Journal of Materials Research | Year: 2014

The 1.3 mm thick plate of ODS high temperature alloy MGH956 was TIG welded with fillers containing different B4C (0, 0.25 and 0.5 mass%), then the effect of B4C content on the microstructure and mechanical properties of the weld joints was investigated. The results show that the microstructure of the weld metal with B4C exhibits mainly equiaxed grains, which are fine and uniform, without significant agglomeration of oxide dispersoids, while the strengthening particulates of the alloy distribute in both grains and grain boundaries. The microstructure of weld joint was finer as the filler with B4C content in a range from 0.25 to 0.5 mass%. However nearly almost the strengthening particulates of the alloy concentrate in the grain boundaries but disappear in the grains for the weld joints by filler with 0.5% B4C. The tensile strength of the weld joints firstly increases and then decreases when the B4C content of the fillers ranged from 0% to 0.5 mass%, but their toughness decreases with the induce of B4C. The tensile strength of the weld joint with filler material containing 0.25% B4C is the highest i.e. 630 MPa, reaching 87.5% of the parent material. The fractured surface exhibited characteristics of brittle fracture. © Copyright. Source


Lei Y.,Jiangsu University | Lei Y.,Jiangsu Province Key Laboratory of High End Structural Materials | Luo Y.,Jiangsu University | Ren D.,Jiangsu University | Liang S.,Jiangsu University
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2014

Trace CO2 was added in the shielding gas during MGH956 alloy arc-ultrasonic TIG welding, and the mechanism and influence law of trace CO2 on the microstructure and properties of the joint were analyzed. The results show that the grains in the weld grew smaller, the porosity in the weld became less, and the tensile strength of the joint increased. Based on the effect of the arc-ultrasonic, after 0.5% CO2 was added in pure Ar, the grains in the weld center were fine-equiaxed and uniformly distributed in the weld, the tensile strength of the joint enhanced significantly, and the joint fracture mode changed from brittle fracture to ductile fracture. Meanwhile, the hardness of the weld increased after trace CO2 was added in the shielding gas, and the comprehensive properties of the joint were improved. Source


Lei Y.,Jiangsu University | Lei Y.,Jiangsu Province Key Laboratory of High End Structural Materials | Zhao K.,Jiangsu University | Huang W.,Jiangsu University | And 2 more authors.
Jiangsu Daxue Xuebao (Ziran Kexue Ban)/Journal of Jiangsu University (Natural Science Edition) | Year: 2014

Tungsten insert gas (TIG) weldings of MGH956 alloy plates with 1.3 mm thickness were conducted with base metal (BM) and self-made high Ni wire as fill materials, respectively. The two kinds of joint microstructures and mechanical properties were compared and analyzed. With high Ni wire as fill material in the process of welding, grain refinement is realized in weld joint with reduced holes, and new composite reinforced phase by TiC is produced in the joint to ensure the joint quality and to reduce the agglomerate of nano-scale reinforced Al-Y-O composite oxide particles. The mechanical testing results show that tensile strength of the sample welded by BM welding is only 57% of that of BM with softening at weld metal (WM). Hardening appears at WM for filling high Ni wire, and the tensile strength of 581 MPa reaches about 80.7% of that of BM. The two cases of heat affected zone hardness are equal to that of BM, and the fracture surface of two weld joints both exhibit brittle fracture. Source


Luo Y.,Jiangsu University | Lei Y.-C.,Jiangsu University | Lei Y.-C.,Jiangsu Province Key Laboratory of High End Structural Materials | Gong C.-C.,Jiangsu University | Liang S.-Y.,Jiangsu University
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2015

In order to improve the microstructure and properties of MGH956 alloy TIG weld, the alloy was welded with TIG in-situ alloying. The effects of V on the microstructure and properties of MGH956 alloy weld were studied, and the mechanism of V was discussed. The OM and SEM results show that the microstructure of the welds are refined and homogenized with different content of V added in the consumables, and as wV =1.5%, the grain size is the smallest and the most uniform. At the same time the weld porosity is the lowest. The EDS results show that there are (Ti, V) C particles generated in addition to YAlO3, TiC, TiN particles in the weld. It can be observed by TEM that the interface between carbide particles and the matrix is clean and joins well. The strength of the weld is the highest when wV=1.5%, and the fracture mode of the joints changes from complete brittle fracture to ductile fracture. ©, 2014, Cailiao Gongcheng/Journal of Materials Engineering. All right reserved. Source


Luo Y.,Jiangsu University | Lei Y.,Jiangsu University | Lei Y.,Jiangsu Province Key Laboratory of High End Structural Materials | Huang W.,Jiangsu University | Liang S.,Jiangsu University
Cailiao Kexue yu Gongyi/Material Science and Technology | Year: 2014

To reduce the porosity of MGH956 alloy in the weld, the arc-ultrasonic excited by modulating TIG arc through high frequency was applied in MGH956 alloy gas tungsten arc welding. The action mechanism and functionary mechanism of arc-ultrasonic on pores and tensile strength of the joints of MGH956 alloy in TIG welding was studied by introducing arc-ultrasonic at different excitation frequency. The movement of the porosity in the weld was analyzed by mathematical theory, the calculation conclusion is consistent with the experimental result that when the excitation current is 15 A, the excitation frequency decreases at 30 kHz, the number of pores is least and the tensile strength reaches the maximum as 521 MPa, reaching to 76% of the tensile strength of base metal, and the fracture mode of the joint changes from completely brittle fracture to brittle-ductile mixed fracture. ©, 2015, Harbin Institute of Technology. All right reserved. Source

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