Authors: Hong Yan, Zhi Hu, Zeng Pan
Abstract: The perfect semi-solid magnesium alloy had been prepared using ultrasonic stirring
method. The effect of technological parameters such as melt temperature, ultrasonic power and
ultrasonic treatment time on the microstructure of semi-solid AZ61 alloy had been investigated. The
results showed that the better refined and well-distributed globular semi-solid magnesium alloy had
been acquired with the increasing of output power of ultrasonic stirring when melt temperature and
ultrasonic treatment time were at a certain range.
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Authors: Zhi Qiang Zheng, Xin Gen Xiong, Ke Ming Chen, Bo Jun Lin, Xu Wen Li
Abstract: The tube spread around strong cooling technology is new technology of the making semisolid slurry and semisolid billet in Semi-Solid Processing. The technologic parameter of its on the A356 Alloy is researched in the article. It is showed by the result of the experimentation: that the fine and form verge on rotundity crystal grain is made at 180L/h and at 640-650°C. It has met all the conditions in the semi-solid processing on semisolid billet. Semi-solid forming technology has been called the "new metal processing technology in the 21st century", which in foreign countries has certain industrial applications. In 1996 in the United States the sales of semi-solid casting was up to 1 billion dollars. But the industrial application in China is almost empty, one of the most important reasons is: the preparation of slurry or billet is too complicated or cost of production is too high, so that semi-solid forming technology in China has suffered serious setbacks on the road of industrialization. According to this situation, we have done a little attempts on manufacturing slurry and billet of semi-solid forming and have developed a new technology of spread around strong cooling whose intellectual property rights belong to us, equipment production is simple and the process is easy to control and the semi-solid slurry is east to prepare continuously. It will be discussed in this paper that process parameters of the single-tube strong cooling impacts on the microstructure of semi-solid
98
Authors: Zhan Yong Zhao, Ren Guo Guan, Fu Rong Cao, Li Qing Chen
Abstract: The influence of the interfacial friction on the continuous rheo-forming microstructures of magnesium alloy. The effects of interfacial friction on the microstructure evolution in magnesium alloy were investigated. It was shown that strong shear stress and internal friction occur inside the melt under the interfacial friction. In roller-shoe chamber, the growth direction of dendrites growing along the normal direction of the roller near the roller-shoe is changed under shear stress and melt resistance force. when the degree between dendrite and normal direction of roller is about 45 degree, the dendrites can be stablized and grow easily along this direction. Under an appropriate pouring temperature, with the increase of pouring temperature, there is enough room for the grains near the roller-shoe to grow, the grains are not easy to collide mutually, so the dendrites form. In roller-shoe chamber, coarse dendrites near the roller become gradually refined when they grow into the mushy region. Moreover, because dynamic friction force and shear stress of roller are stronger at the exit of the chamber, dendrites fracture and fracture layer or cracks appears. The microstructures consist of mainly rosette and spherical grains on the central position.
659
Authors: Salman Nourouzi, Amin Kolahdooz, Mohammad Botkan
Abstract: This investigation studied semi-solid (SSM) aluminum-silicon alloy produced by mechanical stirring. Aluminum alloys produced by this method, are widely used instead of conventional die casting and forging processes. In this research by using a mechanical stirrer slurry maker, the effects of stirring speed, the solid fraction percent and mold temperature are investigated on micro-structure and hardness of A356 aluminum alloy in semi-solid casting. By optimizing the forming parameters, dendrite microstructure changes to globular and mechanical properties improves. This is because of breaking and globularizing dendrites of primary α-AL phase. It is determined that stirring temperature of 608°C and stirring speed of 300 RPM leads to the uniform grains distribution and therefore arrives to better hardness for the produced billets.
331
Authors: Farshid Marani, Behzad Niroumand
Abstract: Semisolid casting and non-dendritic solidification of commercially pure tin (about 1 °C freezing range) and Zamak 3 alloy (about 10 °C freezing range) by a modified serpentine channel method were studied. It was shown that semisolid casting of very small freezing range metals with a non-dendritic structure was possible using this method. The results showed that the wall of the copper serpentine channel mold acted as a substrate for heterogeneous copious nucleation of primary solid particles and the channel provided sufficient self-steering action to disperse the nuclei in the melt. The average diameter and shape factor of the primary particles in the semisolid cast CP-Sn sample was measured to be about 107 μm and 0.75, respectively. The average diameter and shape factor of the primary particles in the semisolid cast Zamak 3 alloy was measured to be about 16 μm and 0.8, respectively. Hardness of semisolid samples was slightly higher than those of conventional gravity cast samples.
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