Papers by Author: Xiao Qiu Zheng

Abstract: The influences of heating temperature and holding time on the microstructures were investigated during the semi-solid remelting process of rare earth Al-4.5Cu alloy. The evolution mechanism of crystal organization was discussed. Experiments show that the heating temperature and holding time are very important to the grain size and uniformity. It is the most suitable parameters, as heating temperature is 630°C and holding time is 20 minutes, to remelting process. During the remelting process, grain mergering and Ostwald growing up is the main mechanism of change on microstructures.

Abstract: Gd substrates were differently coated with Ti and 1Cr18Ni9Ti by means of DC magnetron sputtering technology. The characteristics of the films have been investigated by scanning electron microscopy(SEM), EDS,X-ray photoelectron spectroscopy(XPS),and the adhesion of films were tested by tension test. The results show that the surfaces of films are smooth and perfect, the interferences between Gd and films join together strongly, and the adhesion strengths are larger than 15MPa in these tests.

Abstract: In order to research the adhesion of sputtering protective coating of Gd. Gd substrates were differently coated with 1Cr18Ni9Ti, Ti, Cu and Al by means of DC magnetron sputtering technology. The characteristics of the films were investigated by scanning electron microscopy (SEM), EDS, and the adhesions of films were tested by tension test. The results show that the films of 1Cr18Ni9Ti, Ti and Al are smooth and perfect, the interferences between 1Cr18Ni9Ti, Ti, Al and Gd join together strongly, and the average strength of adhesion is 25MPa in these tests on the optimize parameters. While the films of Cu are rough and bad, the interferences between Cu and Gd join together loosely, and the largest strength of adhesion is only 3.02MPa in these tests on the optimize parameters.

Abstract: In order to research the adhesion of sputtering protective coating of Gd. Gd substrates was coated with 1Cr18Ni9Ti by means of DC magnetron sputtering technology. The characteristics of the film were investigated by scanning electron microscopy (SEM), EDS, SPM and the adhesions of film was tested by tension test. The results show that the films of 1Cr18Ni9Ti are distributed by means of islands when the sputtering was initiated and the grains are like thin fiber. After a few minutes, the films are smooth and perfect, the interferences between 1Cr18Ni9Ti and Gd join together strongly, and the largest strength of adhesion is 24.7MPa when the sputtering density is 966 w/cm2 and the sputtering time is 8 minutes.

Abstract: In order to research the adhesion of sputtering protective coating of Gd.Gd substrates were differently coated with Cu and Al by means of DC magnetron sputtering technology. The characteristics of the films were investigated by scanning electron microscopy (SEM), EDS, and the adhesions of films were tested by tension test. The results show that the films of Al are smooth and perfect, the interferences between Al and Gd join together strongly, and the largest strength of adhesion is 27.6MPa in these tests on the optimize parameters through orthogonal experimental design. While the films of Cu are rough and bad, the interferences between Cu and Gd join together loosely, and the largest strength of adhesion is only 3.02MPa in these tests on the optimize parameters through orthogonal experimental design.

Abstract: The fabrication process of refined isometric crystals of semi-solid Al7Si2RE alloy is discussed, and the remelting microstructure of Al7Si2RE alloy with isothermal holding at 580°C is also researched. Experiment shows that the casting temperature, the casting size, the casting mold and the casting method will make great effects on the fabrication of refined isometric crystals alloy microstructure. Slope copper mold casting at liquidus temperature can be used in preparing excellent non-dendritic microstructure billet; its remelting microstructure is uniform, refined isometric crystals with the average diameter of 44.2um and the average roundness of 2.08.

Abstract: In semi-solid remelting process, the various stages of reheating temperature and isothermal holding time must be accurately controlled in order to obtain the uniformly distributed and small equiaxed grains microstructure. In this paper, a temperature control program was developed and the remelting process for Al-7Si-2RE aluminum alloy was carried out. The results showed that with the raise of reheating temperature and the extension of isothermal holding time, the liquid fraction increases, α-phase grain grows and becomes rounding in the process of Al-7Si-2RE alloy semi-solid remelting. The most reasonable process parameter of reheating temperature is at 585~590°C and its appropriate isothermal holding time are about 10~15min for the semi-solid Al-7Si-2RE alloy.

Abstract: Al-4.5Cu-3Ce alloy semi-solid slurry has been prepared by using slope vibration casting. The effects of the pouring temperature, slope length, vibration amplitude and vibration voltage on alloy solidification microstructure were researched. Experiments show that these parameters play a significant role on the alloy microstructure. The uniform, small equiaxed microstructure of Al-4.5Cu-3Ce alloy can be acquired by water-cooled copper mold casting at 680°C with slope length of 20cm, vibration amplitude of 2cm and vibration voltage of 80v. Its average grain diameter is 28.1um with average roundness coefficient of 0.82.

Abstract: The semi-solid slurry of AlSi7 alloy was prepared by near-liquids cast processing. The effects of different content of RE on the cast performance and the semi-solid remelting performance in AlSi7 alloy was researched. The results indicated that adding RE will widen the AlSi7 alloy solid-liquid two-phase zone temperature and refine the grains, silicon will obvious metamorphoses. The best amount of RE is about 0.5%. Its semi-solid remelting organization is equilateral globular grains.

Abstract: SSM(Semi-solid metal) forming has been developed to become a novel technology in the 21st century for the formation of near net shape components, competing with conventional casting and forging technologies. In this paper, the casting microstructure and its change during remelting of AlSi7Cu5 alloy casting by slope near-liquidus method were researched. Experiments show that it has a significant impact on microstructure by cooling method, the thermal conductivity of the casting mold and casting method. The microstructure of AlSi7Cu5 alloy obtained by slope near-liquidus method at 600°C is uniform and small equiaxed Its average grain diameter is about 55.2um, and its average grain size roundness is about 2.13. The reheated microstructure which can be applied in thixo-forming preferable will be obtained by keeping constant temperature 25min at 580°C.