Qing Feng Zhu
Northeastern University
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Featured researches published by Qing Feng Zhu.
Advanced Materials Research | 2010
Qing Feng Zhu; Zhi Hao Zhao; Xiang Jie Wang; Jian Zhong Cui
The effect of increasing the amount of added grain refiner and combination electromagnetic filed on grain size and morphology has been investigated by die casting of commercial aluminum. The results show the grain size and the grain morphology both are transited with the increasing of the addition of Al-5Ti-B. The grain size continuously decreased with increasing the addition of grain refiner. Without grain refiner additions, an obvious transition in grain size and morphology is observed with the application of low frequency electromagnetic field (LFES). The efficiency in grain refinement of LFES decreases with increasing the amount of grain refiner. However, even when the addition of grain refiner is 2 wt. % Al-5Ti-B, 63 % grain size reduction still is observed by the affect of LFES. This result shows that the LFES can enhance the efficiency in grain refinement of grain refiner.
Materials Science Forum | 2014
Qing Feng Zhu; Zhi Hao Zhao; Yu Bo Zuo; Lei Li; Jian Zhong Cui
In this study, a purity of 99.995percent high purity aluminum was multi-directionally forged up to a maximum cumulative strain of 4.5 at room temperature. The macro and micro structure evolution in the multi-directionally forge process was investigated by structure observations and hardness measurements. The results show that the inhomogeneous deformation of multi-directional forging results in that the structure and hardness is quite different between the easy deformation zone and stagnant zone. Dynamic recrystallization occurs in easy deformation zone of high purity aluminum sample at room temperature as the cumulative true strain is 1.5 (3 forging passes), while the structure in the stagnant zone is still not recrystallizated even at a cumulative true strain of 4.5 (9 forging passes). The recrystallized grain size in the easy deformation zone is reduced with the number of forging passes, and the area of recrystallize grains increase with the number of forging passes.
Advanced Materials Research | 2011
Qing Feng Zhu; Zhi Hao Zhao; Xiang Jie Wang; Jian Zhong Cui
7075 aluminum alloy ingot with the diameter of 100 mm has been produced by horizontal direct chill casting in different casting speed. The effect of casting speed on the sump profile and the ingot surface quality was studied by sump profile observation. It was found that increasing the casting speed results in the deepening of the liquid pool, the adding of segregation knots and the reducing of cold shouts in the ingot surface. It is also found that the depth of the liquid pool is directly proportional to the casting speed and the squared radius of the ingot.
Materials Science Forum | 2007
Zhi Hao Zhao; Jian Zhong Cui; Qing Feng Zhu
The horizontal direct chill (HDC) casting process is a well-established production route for an aluminum alloy ingot; however, the ingot may suffer from inhomogeneous microstructures and serious macrosegregation due to the unbalanced cooling condition and gravitational effect. In order to control the defect, a low frequency electromagnetic field has been applied in the HDC casting process and its influences on microstructures and macrosegregation have been studied. The results show that the low frequency electromagnetic field can improve macrostructures, reduce inhomogeneous microstructures and macrosegregation in HDC product; and two main parameters of the electromagnetic field—density and frequency influence the microstructures and solution distribution along the diameter of the ingot significantly. In the range of ampere-turns and frequency employed in the experiments, the optimum ampere-turns and frequency have been found to be 10000At, 30Hz.
Materials Science Forum | 2016
Qing Feng Zhu; Jia Wang; Lei Li; Chun Yan Ban; Zhi Hao Zhao; Jian Zhong Cui
The effects of final forging temperatures on deformability and structure evolution of high purity aluminum during multi-directional forging process were investigated. The results showed that increasing the initial forging temperature is beneficial for controlling the sample shape in the initial forging passes. Recrystallization during the initial forging passes improves the deformability of the sample in the following low-temperature forging processes. An X-shape fine grain zone is formed in the sample due to the inhomogeneous deformation of multi-directional forging process. When the forging pass is 6, the final forging temperature has an important influence on the grain size in the fine grain zone. The grain size decreases from 302 μm to 60 μm with the final forging temperature decreasing from 310 °C to 65 °C. The X-shape fine grain zone caused by the inhomogeneous deformation cannot be eliminated by increasing the final forging temperature (even higher than the recrystallization temperature of high purity aluminium).
Materials Science Forum | 2016
Zhi Hao Zhao; Qing Qiang Chen; Qing Feng Zhu; Wen Qiang Liu; Gao Song Wang
The 6xxx series aluminium alloy wires (with the diameters of 2.84 mm) produced by the continuous drawing and rotary-wheel continuous casting, were directly aged in different conditions. The results show that, when ageing temperature is at 150°C, the tensile strength of the wire firstly decreased from 283 MPa to 265 MPa as the ageing time extended from 0 to 4 hours, and then increased from 265 MPa to 270 MPa as the ageing time extended from 4 to 12 hours, and finally decreased from 270 MPa 263 MPa as the ageing time extended from 12 to 24 hours. The electrical resistively of the wires continued decreases with the ageing time extend from 0 to 24 hours. When the ageing temperature is at 160, 170, 180 and 190 °C, both the tensile strength and the electrical resistively of the wire continuously decreased with the ageing time extended from 0 to 24 hours. When the ageing time was identical, the wires with higher ageing temperature possessed lower tensile strength and electrical resistively.
Materials Science Forum | 2016
Yu Bo Zuo; Qing Feng Zhu; Lei Li; Guang Ming Xu; Jian Zhong Cui
A low frequency electromagnetic field was introduced into the direct chill (DC) casting process and the ingots of Al-Cu alloy were prepared to study the macrosegregation behaviour of the ingots under the influence of the electromagnetic field. The experimental results showed that there is an obvious positive segregation near to the surface and a negative segregation in the centre area of the ingot. Cu shows the highest segregation tendency among the main elements of Cu, Mg and Mn. Grain refiner element Ti shows a segregation trend opposite to that of Cu. With the application of electromagnetic field, the negative centreline segregation in the centre area of the ingot was evidently reduced although it didn’t show significant effect on the segregation near to the ingot surface. A significant grain refinement was also achieved with the application of electromagnetic field. The mechanism of the reduction of macrosegregation with electromagnetic field was also analyzed in the present work.
Materials Science Forum | 2015
Qing Feng Zhu; Wen Jing Wang; Zhi Hao Zhao; Yu Bo Zuo; Jian Zhong Cui
A purity of 99.995% high purity aluminum was deformed by multi-forging with different conditions (forged by different forging passes with and without water cooling). The effect of multi-forging on macrostructure and mechanical property of the high purity aluminum was investigated. The results show that the deformation heat during the MDF process can obviously affect the recrystallization of the high purity aluminum. Recrystallization occurs in the easy deformation zone of the sample as forged by 3 passes at room temperature. While, when the sample are cooling by water for each pass, no recrystallization occurs in the whole sample as forged by 9 passes. When the high purity forged at room temperature, the structure difference between the easy deformation zone and stagnant zone can not be eliminated by increasing the forging pass to 9. While, the area of the recrystal grain extends with increment of the forging pass.
Applied Mechanics and Materials | 2014
Xiao Ming Wang; Sheng Zhu; Jian Zhong Cui; Qing Chang; Qing Feng Zhu
To develop high wear-resistant protective materials for magnesium alloy, high-silica Al-based alloy modified via P-element was fabricated by DC casting method. Microstructure of ingot samples was observed by using optical microscopy (OM), etc. The results demonstrated that Al-Si-0.01%P alloy with unique microstructure and without defects such as voids and rarefaction might be generated by processing control. Owing to modification by Al-P interalloy, primary crystal silicon phase in hypereutectic Al-Si alloy were refined effectively. Its size in Al-18Si-0.01%P alloy decreased from 50μm to 20μm, and distributed uniquely than that in Al-18Si alloy. Al-P acted as heterogeneous core of primary crystal silicon phase, which was the main mechanism for Al-P interalloy to modify primary crystal silicon in Al-Si alloy.
Materials Science Forum | 2013
Qing Feng Zhu; Zhi Hao Zhao; Yu Bo Zuo; Lei Li; Jian Zhong Cui
2024 Al alloy ingot with diameter of 100 mm is produced by conventional and combined electromagnetic fields (CEMF) horizontal direction chill (HDC) casting processes. The effect of CEMF on the ingot structure is investigated. The results show that the CEMF is effective in changing the inner structure of the 2024 HDC cast ingot. In the conventional HDC ingot, feathery grains mainly distribute over the majority of the area of the ingot, and coarse equiaxed grains mixed with coarse floating grains distribute in a crescent-shaped area near the bottom surface. With the application of the CEMF, the majority of the feathery grains transform to fine equiaxed grains, and the mixture of feathery and fine grains only exist in the area near the upper surface. In addition, the coarse floating grains completely disappeared in the ingot with the application of CEMF.