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47 results on '"Gao, Minqiang"'

31. Nucleation and growth behavior of primary Al11Ce3intermetallic compounds during solidification in a hypereutectic Al–Ce alloy

Author

Ye, Jieyun, Xiao, Jinrong, Gao, Minqiang, and Guan, Renguo

Abstract

In this study, the nucleation and growth mechanisms of Al11Ce3intermetallic compounds (IMCs) in a hypereutectic Al–Ce alloy during solidification were investigated through synchrotron radiation X-ray real-time imaging. The results showed that Al11Ce3IMCs nucleate and grow from the melt as the primary phase at the initial stage of solidification. Growth preferred orientations were observed in two opposite directions, resulting in an I-shaped growth pattern. Based on the minimum energy criterion, the morphology of Al11Ce3IMCs displayed either hollow cubic tubes or grooves. The nucleation and growth rates of Al11Ce3IMCs gradually decreased over time, owing to the variations in the Ce concentration in the melt and the undercooling. The nucleation and growth characteristics of Al11Ce3IMCs can provide the theoretical basis for optimization on the performance of Al–Ce alloys.

Published
2024
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39. Microstructure evolution, diffusion behavior, and mechanical properties of a Cu/AlCoCrFeNi2.1composite under pulsed magnetic field

Author

Sun, Wanting, Fu, Ying, Gao, Minqiang, Zhang, Junjia, Kong, Xiangqing, and Guan, Renguo

Abstract

A Cu/AlCoCrFeNi2.1composite was fabricated via solid-liquid method. In order to acquire the good interface bonding, the pulsed magnetic field (PMF) treatment was applied during the preparation of the Cu/AlCoCrFeNi2.1composite. The effects of different processes and parameters, including pulse frequency on the interface microstructure, element distribution, diffusion thickness, and mechanical properties of the composite were investigated. The results demonstrated that PMF treatment effectively decreased the diffusion layer thickness of the composite, and improved mechanical properties of the Cu side. The diffusion thickness of the composite reduced from 31.22 μm to 6.20 μm after applying PMF. The action mechanism of PMF during preparation was revealed. The ultimate tensile strength, yield strength, and elongation of the Cu/AlCoCrFeNi2.1composite via PMF were 192.6 MPa, 121.7 MPa, and 43.8%, respectively, which were higher than that of the composite without PMF. The maximum shear strengths of the composites with and without PFM were 120.2 MP and 137.4 MPa, respectively. When the pulse frequency was 2 Hz, the macro-segregation was eliminated to form the high-quality interface. This work paves a way for the performance improvement and complex parts preparation of layer composite by using PMF.

Published
2023
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45. Cementites decomposition of a pearlitic ductile cast iron during graphitization annealing heat treatment

Author

Jun-hua You, Li Guanglong, Ying-dong Qu, Rongde Li, and Gao Minqiang

Subjects
Materials science, Annealing (metallurgy), Scanning electron microscope, Metallurgy, Metals and Alloys, 02 engineering and technology, engineering.material, Microstructure, 020501 mining & metallurgy, 0205 materials engineering, Mechanics of Materials, Ultimate tensile strength, Materials Chemistry, engineering, Cast iron, Elongation, Ductility, Tensile testing
Abstract

Cementites decomposition of a pearlitic ductile cast iron during graphitization annealing heat treatment was investigated. Fractographies and microstructures of heat treated samples were observed using a scanning electron microscope and mechanical properties were measured by a universal tensile test machine. The results indicated that during isothermal annealing at 750 °C, the tensile strength of pearlitic ductile cast iron was increased to a peak value at 0.5 h, and decreased gradually thereafter but the elongation was enhanced with the increase of annealing time. Moreover, the diffusion coefficient of carbon atoms could be approximately calculated as 0.56 µm2/s that could be regarded as the shortrange diffusion. As the holding time was short (0. 5 h), diffusion of carbon atoms was incomplete and mainly occurred around the graphites where the morphology of cementites changed from fragmentized shape to granular shape. In addition, the ductile cast iron with tensile strength of 740 MPa and elongation of 7% could be achieved after graphitization annealing heat treatment for 0. 5 h. Two principal factors should be taken into account. First, the decomposition of a small amount of cementites was beneficial for increasing the ductility up to elongation of 7%. Second, the diffusion of carbon atoms from cementites to graphites could improve the binding force between graphites and matrix, enhancing the tensile strength to 740 MPa.

Published
2017

47. Ultra-Long Pore Fabrication Process by Pulling–Casting in Aluminum Alloy

Author

Jun-hua You, Qu Yingdong, Sun Fengshuang, Qin Gang, Jin Meiling, Li Rongde, and Gao Minqiang

Subjects
Fabrication, Materials science, Mechanical Engineering, Alloy, Microporous material, engineering.material, Casting, Aspect ratio (image), Industrial and Manufacturing Engineering, Surface tension, Mechanics of Materials, engineering, General Materials Science, Fiber, Wetting, Composite material
Abstract

The main preparation methods of ultra-long pores are carried out by mechanical or special processing over a long time, and by the casting method the aspect ratio of pores is smaller than 2. In the present article, according to weak wettability between carbon fiber and aluminum, carbon fiber was chosen as the pore-forming material then ultra-long pores were fabricated successfully by means of pulling–casting. The experimental result demonstrated that the pore aspect ratio was 495, and pore diameter was about 0.222 mm. Theoretical analysis shows that the effect of surface tension on invalid pore length can be neglected – this value was only 0.01 mm. X-ray diffraction results showed that there was almost no chemical reaction between aluminum and carbon fiber bundles, which means that undamaged carbon fiber was beneficial for pulling. Otherwise, because the carbon fiber was in a loose state previously and there were differences between actual measurement diameter and theory diameter after pore formation, loos...

Published
2014

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