Zheng LIU
金属学报(英文版)
doi:10.1016/S1006-7191(08)60118-0
Semi-solid slurry of A356 alloy was prepared by low superheat pouring and slightly electromagnetic stirring, and the fractal characteristics of morphology in semi-solid primary phase was researched. The fractal dimensions of primary phase morphology in the semi-solid A356 alloy were calculated by the program written to calculate the fractal dimensions of box-counting in the image of solid phase morphology in semi-solid metal slurry. The results indicated that the morphology of primary phase in semi-solid A356 prepared by low superheat pouring and slightly electromagnetic stirring is characterized by fractal dimension, and the primary phase morphology obtained by the different processing parameters has different fractal dimensions. The morphology of primary phase at the different position of ingot has different fractal dimensions, which reflected the effect of solidified conditions at different positions in the same ingot on the morphology of semi-solid primary phase. Solidification of semi-solid alloy is a course of change in fractal dimension.
关键词:
Semi-solid
,
初生相形貌
,
分形
,
A356铝合金 semi-solid, morphology of primary phase, fractal, A356 alloy
Zheng LIU
金属学报(英文版)
Semi-solid Al7Si0.3Mg alloy slurry, which is grain-refined by yttrium, is manufactured by low temperature pouring. The effects of grain-refined by yttrium on the morphology and the grain size of the primary α-Al in semi-solid Al7Si0.3Mg alloy are researched. The results indicate that semi-solid Al7Si0.3Mg alloy with particle-like and rosette-like primary α-Al can be prepared by low temperature pouring from liquid Al7Si0.3Mg alloy grain-refined by yttrium. The grain size and particle morphology of primary α-Al in Al7Si0.3Mg alloy are markedly improved by 0.5 wt pct Y. The refining mechanism of Y on the morphology and the grain size of the primary $\alpha$-Al in semi-solid Al7Si0.3Mg alloy are delved.
关键词:
Semi-solid
,
钇
,
Al7Si0.3Mg合金
,
细化机制
null
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null
,
null
,
null
金属学报(英文版)
The semi-solid AlSi7Mg alloy slurry of large size was prepared by the low superheat pouring and weak electromagnetic stirring in this paper. The effects of pouring temperature and stirring power on the microstructure of the AlSi7Mg alloy slurry were studied. The results show that the semi-solid AlSi7Mg alloy slurry of 127mm in diameter can be prepared by the low superheat pouring and weak electromagnetic stirring technology and this new technology can save energy and make the pouring process convenient. When the liquid AlSi7Mg alloy is poured at 650 or 630, the solidified microstructure of the AlSi7Mg alloy slurry prepared by the weak electromagnetic stirring is remarkably improved compared with that of the slurry without stirring, the primary -Al grains appear rosette-like or spherical. When the pouring temperature is decreased, the shape of the primary -Al grains is gradually changed from dendritic-like grains to spherical grains. When the pouring temperature is appropriately increased, namely raised to a certain superheat, the pouring process becomes easier and an ideal spherical microstructure of the AlSi7Mg alloy slurry prepared by the weak electromagnetic stirring can also be obtained, in this experiment, when the stirring power is 0.36kW, the optimized pouring temperature parameter is 630.When the AlSi7Mg alloy slurry is prepared by the low superheat pouring and weak electromagnetic stirring, when the pouring temperature is 630,increasing the stirring power appropriately could gain better spherical primary -Al grains,but if the stirring power is increased to a certain value, the shape of the primary 冄-Al grains is not further improved, in this experiment, the optimized stirring power parameter is 0.36kW.
关键词:
Semi-solid
,
null
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null
,
null
,
null
Zesheng JI
,
Maoliang HU
,
Xiaoping ZHENG
材料科学技术（英文）
To investigate the thixotropic fluidities, microstructures and mechanical properties of semi-solid AZ91D magnesium alloy during reheating, a self-made die set with channels of different sizes were used. The results show that critical forming forces and maximal forming forces could be obtained and related to the holding times in the semi-solid forming process. In the holding time of 0-2700 s, with increasing the holding time, maximal forming force decreased sharply and critical forming force decreased slowly. In the whole thixotropic flowing process, the filling-in was steady and the surface fineness was good. The forming force increased when the slurry changed the flowing direction or flowed from the big-diameter chamber to the small-diameter one. The tensile strength and elongation to failure of the sample after holding time for 2700 s, compared to as-cast sample, are increased by approximately 42.7% and 180%, respectively, and the fractured surfaces presented dimple-like pattern.
关键词:
AZ91D magnesium alloy
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magnesium
,
alloy
,
semi-solid
,
thixot
Weimin MAO
材料科学技术（英文）
The effects of pouring temperature, short electromagnetic stirring with low strength and then soaking treatment on the microstructure of AlSi7Mg alloy were investigated. The results show that if AlSi7Mg alloy is poured at 630 or 650℃ and meanwhile stirred by an electromagnetic field at a low power for a short time, the pouring process can be easily controlled and most solidified primary α-Al grains become spherical and only a few of them are rosette-like. Weak electromagnetic stirring makes the temperature field more homogeneous and makes the primary α-Al grains disperse in a larger region, which leads to the spherical microstructures of primary α-Al grains. When the AlSi7Mg alloy is soaked or reheated at the semisolid state, the primary α-Al grains ripen further and they become more spherical, which is favorable to the semi-solid forming of AlSi7Mg alloy.
关键词:
AlSi7Mg alloy
,
alloy
,
semi-solid
,
pouring
,
tempera
Weimin MAO
,
Aimin ZHAO
,
Dong YUN
,
Leping ZHANG
,
Yonglin KANG
材料科学技术（英文）
The nondendritic semi-solid slurry preparation of 60Si2Mn spring steel has been studied in this paper. The experiments have shown that when stirred for 2 min on the test condition, the semi-solid slurry with 50%~60% fraction solid and spherical primary austenitic grains in the size of 100~300 μm can be obtained and is easy to be discharged from the bottom little hole of the stirring chamber. The nondendritic slurry of 60Si2Mn spring steel can be rolled into given plate form successfully, but the solid phase and liquid phase is easy to be separated in rolling process so that the solid primary austenite is concentrated in the center and the liquid is near the edge of the rolled plate. The rupture strength and elongation of the plate rolled only once with semi-solid slurry are lower than that of the traditionally repeated hot-rolled plate of 60Si2Mn spring steel.
关键词:
60Si2Mn
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null
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null
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null
