Papers by Author: Xiao Mei Liu

Abstract: Based on the green and saving concept, a complex process preparing semisolid alloy slurry was developed, which was composed of the low superheat pouring and low frequency electromagnetic stirring. The semisolid A356-La slurry was prepared by the complex process, and the microstructure of the semisolid A356-La alloy was researched under the different preparing parameters in the complex process, such as the pouring temperature, electromagnetic stirring frequency, stirring time and micro-addition of La. The results indicated that it was feasible to reduce the addition of La and consumption of energy during the preparation of semisolid alloy slurry by optimizing the preparing parameters in the complex process. The suitable preparing parameters were obtained by the experiment, in which the pouring temperature was 630 °C, the frequency of electromagnetic stirring was 30 Hz, and the stirring time was 8 s. When semisolid A356 alloy slurry added 0.3 wt% La was prepared by the suitable preparing parameters in the complex process, the refining effects on microstructure in the semisolid A356-0.3La alloy was indistinguishable with that of the conventional addition amount of 0.6 wt% La in semisolid A356 alloy prepared by low superheat pouring.

Abstract: Semisolid A356 alloy was prepared by low superheat pouring, and evolution of primary phase morphology in semisolid A356 alloy during isothermal holding was characterized by fractal theory. The results indicated that the primary phase morphology in the alloy had fractal character, and the evolution of the primary phase morphology in the alloy could be characterized by fractal dimension. The primary phase morphology at the different isothermal holding temperature and holding time had the different fractal dimension, which meant the effect of processing conditions on the morphology in the alloy. Solidification of the alloy was a course of change in fractal dimension.

Abstract: Mg2Si particle reinforced hypereutectic Al-Si composite was prepared by casting, and the microstructure and wear resistance of the composite were researched. The results indicated that the morphology of Mg2Si obviously changed with Mg2Si contents increasing, in which the morphology of Mg2Si in the composite had changed from polygon block to characters like and finally became coarse dendrite. There were effects of Mg2Si content and morphology on the wear resistance in the composite, which had the higher hardness and better wear resistance at the suitable Mg2Si content.

Abstract: The effects of the interface in alumina fiber reinforced Al-Si alloy composites prepared by squeeze casting on the wear resistance of the composites were studied. The results indicated that the fiber combined with the matrix well in the composites and had reinforcing effect on the alloy. The interface in the composites could hold back crack propagation, and the composites had the excellent wear resistance. The alloy elements in the matrix were favourable to forming the good interface to improve wear resistance of the composites.

Abstract: Semisolid alloy slurry was prepared by an efficient and energy-saving technology which consists of low superheat pouring and slightly electromagnetic stirring (LSPSES). The effects of the main preparing parameters on the slurry were researched. The results indicate that the slurry to satisfy rhoe-forming needed can be prepared by LSPSES. The pouring temperature and the stirring power remarkablely affect the morphology and size of primary α-Al in semisolid Al alloy slurry. Through the suitable slightly electromagnetic stirring, the pouring temperature can be suitably raised to reach the efficient and energy-saving effectiveness.

Abstract: The effects of complex modifier (consisted of mixed rare earth oxides and CaCO₃) on microstructure in Mg₂Si/A1-Si composite are researched. The results show that the morphology of Mg₂Si particle changes from irregular or crosses to polygonal shape, and its size obviously decreases. The modifier presents the better modification than mixed rare earth oxides or CaCO₃.

Abstract: Mg2Si particle reinforced in-situ Al-Si composite is prepared by melt superheating, and the microstructure and properties of the composite are researched. The results indicate that it is feasible that the melt superheating is applied to preparing Mg2Si particle reinforced in-situ Al-Si composite, and the suitable preparing parameters of melt superheating on the alloy are obtained. When the superheating temperature is 860°C and holding time is 25 min, the average size of Mg2Si particle in the alloy will be reduced to 11μm compared with 34μm without melt superheating, and the mechanical properties of the composite is obviously improved.

Abstract: The fractal characteristic of microstructure in semisolid A356 alloy was researched by the calculating program written to calculate the fractal dimensions. The results indicated that the morphology of primary grain in semisolid A356 prepared by compound process is characterized by fractal dimension, and the morphology of primary grain at the different position of ingot had the different fractal dimensions, which reflected the effect of solidified conditions at different position in the same ingot on the morphology of semisolid primary grain.