Research on fractal characteristics of primary phase morphology in semi-solid A356 alloy

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.     

Effect of Grain-Refined on Primary α Phase in Semi-Solid A356 Alloy Prepared by low superheat Pouring and Slightil Electromagnetic Stirring

The semi-solid slurry of A356 alloy, which is grain-refined by Al-Ti-B master alloy, is prepared by low superheat pouring and slight electromagnetic stirring. The effects of grain refining on the morphology and the grain size of the primary α phase in the slurry manufactured are researched. The results indicate that the slurry with particle-like and rosette-like primary α phases can be prepared by low superheat pouring and slight electromagnetic stirring from liquid A356 alloy grain-refined, in which the pouring temperature can be suitably raised. Compared with the A356 samples without grain refining, the grain size and particle morphology of primary α phase as well as the distribution of the grain with particle-like or rosette-like along radial in the ingot in A356 are markedly improved by grain refining.     

EFFECT OF GRAIN REFINING ON PRIMARY α PHASE IN SEMI-SOLID A356 ALLOY PREPARED BY LOW SUPERHEAT POURING AND SLIGHT ELECTROMAGNETIC STIRRING

The semi-solid slurry of A356 alloy, which is grain-refined by Al-Ti-B master alloy, is prepared by low superheat pouring and slight electromagnetic stirring. The effects of grain refining on the morphology and the grain size of the primary α phase in the slurry manufactured are researched. The results indicate that the slurry with particle-like and rosette-like primary α phases can be prepared by low superheat pouring and slight electromagnetic stirring from liquid A356 alloy grain-refined, in which the pouring temperature can be suitably raised. Compared with the A356 samples without grain refining, the grain size and particle morphology of primary α phase as well as the distribution of the grain with particle-like or rosette-like along radial in the ingot in A356 are markedly improved by grain refining.     

Effect of pouring temperature on semi-solid slurry of ZL101 alloy prepared by slightly electromagnetic stirring

The semi-solid slurry of ZL101 alloy is prepared by a combination technology of low superheat poudng and slightly electromagnetic stirring. The effects of pouring temperature on the slurry prepared by the technology are investigated. The results indicate that it is feasible to prepare the slurry with globular primary phases by low superheat pouring and slightly electromagnetic stirring, and that the pouring temperature has an important effect on the morphology and the size of primary α-Al in ZL101 alloy. By applying suitable slightly electromagnetic stirring combining with relatively increased pouring temperature, i.e., in a practical way to apply low superheat pouring technology, is capable of obtaining appropriate semi-solid slurry of ZL101 alloy with globular shape of primary phase. Compared with the samples made by low superheat pouring only without stirring, the samples prepared by applying both slightly electromagnetic stirring and low superheat pouring can enable to achieve the same grain size and morphology of the primary phase with that of pouring at 15-35℃ higher.     

Manufacture technique of semi-solid slurry of hypoeutectic Al-Si alloy by low superheat pouring and weak electromagnetic stirring

Semi-solid metal (SSM) process is a relatively new technology that offers distinct advantages over other near-net-shape casting processes, such as a more homogeneous microstructure, less porosity and segregation, and improved mechanical properties[1-3]. SSM can be divided into thixoforming and rheoforming, in which rheoforming is usually advantageous from the point of view of an energy and cost saving when compared with thixoforming, so rheoforming has been paid attention again by engineers i…     

Effect of local chilling on morphology of primary α (Al) in semi-solid A356 alloy

The semi-solid slurry of A356 alloy was prepared by low superheat pouring and slightly electromagnetic stirring, in which a pure copper rod was used to produce local chilling. The effect of chilling by the rod on morphology and size of primary α (Al) in A356 was researched. The results indicate that the chilling by the rod remarkably affects the morphology and the size of primary α (Al). Primary α (Al) with particle-like shape is distributed uniformly in A356, and there is no transient area in structure morphology. Compared with the samples prepared without the local chilling, the nucleation rate, morphology and grain size of primary α (Al) in A356 prepared by low superheat pouring and slightly electromagnetic stirring with the rod are markedly improved. Under the condition of chilling, the pouring temperature can be suitably raised to obtain primary α (Al) with particle-like shape.     

Research on semi-solid slurry of a hypoeutectic Al-Si alloy prepared by low superheat pouring and weak electromagnetic stirring

The semi-solid slurry of a hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouting temperature and stirring power on the semi-solid slurry were investigated. The results indicated that the semi-solid slurry to satisfy rheocasting can be manufactured by low superheat pouring and weak electromagnetic stirring. The pouring temperature （or superheat） and the stirring power remarkably affected the morphology of primary α-Al and the size of primary α-Al, and there is no obvious effect of stirring time on primary α-Al. Compared with the samples made by low superheat pouring with no stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 were markedly improved by low superheat pouring and weak electromagnetic stirring. On the condition of weak electromagnetic stirring, the pouring temperature with low superheat can be suitably raised to reach the effectiveness obtained from the lower pouring temperature without stirring.     

Effect of yttrium on the microstructure of a semi-solid A356 Al alloy

The semi-solid slurry of an A356 Al alloy,which was grain-freed by yttrium,was manufactured by low temperature pouring.The effects of grain-refining on the morphology and the grain size of the primary α phase in the semi-solid A356 Al alloy were researched.The results indicate that the semi-solid A356 Al alloy with particle-like and rosette-like primary α-Al can be prepared by low temperature pouring from a liquid grain-refined A356 alloy.The grain size and particle morphology of primary α-Al in the A356 Al alloy are markedly improved by the addition of 0.5 wt.% Y.The fining mechanism of Y on the morphology and grain size of the primary α-Al in the semi-solid A356 Al alloy was delved.     

Preparation of Semi-Solid AlSi7Mg Alloy Slurry

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.     

高效节能制备半固态合金浆料的新工艺

应用高效节能的工艺制备了半固态合金浆料,该工艺采用了低过热度浇注和弱电磁搅拌。研究了主要工艺参数对半固态合金浆料的影响。结果表明,低过热度浇注和弱电磁搅拌工艺可制备满足流变成形所需的半固态合金浆料,浇注温度和搅拌功率显著影响初生α-Al晶粒的形貌和尺寸。通过对合金熔体的弱电磁搅拌,可适当提高低过热度浇注的温度,实现高效和节能的目的。     

6061铝合金半固态浆料的行波电磁搅拌制备工艺

采用低过热度浇注和弱行波电磁搅拌工艺,成功制备出6061铝合金半固态浆料。研究了浇注温度、搅拌功率和搅拌时间对6061铝合金半固态浆料的影响。结果表明:低过热度浇注和弱行波电磁搅拌技术可获得具有良好球状初生α-Al的6061合金半固态组织。浇注温度接近液相线温度,搅拌功率大于2.5kW,搅拌时间大于10s时,6061铝合金半固态浆料中的初生α-Al细小圆整,尺寸均匀。但是当浇注温度降至液相线温度时,组织中出现少量树枝晶。最佳工艺参数:浇注温度667℃、搅拌功率2.5kW、搅拌时间10s。     

Preparation of semi-solid AlSi7Mg alloy slurry with big capability

Semi-solid AlSi7Mg alloy slurry was prepared by low superheat pouring and weak traveling-wave electromagnetic stirring.The effects of pouring temperature and stirring power on the microstructure of AlSi7Mg alloy slurry were studied.The results show that the semi-solid AlSi7Mg alloy slurry of 5 kg can be prepared.This new technology can save energy and make the pouring process convenient.When the pouring temperature is decreased at a stirring power of 0.41 kW,the shape of primary α-Al grains gradually changes from dendritic-like to spherical.When the alloy melt is poured at the temperature(630°C) with a certain superheat,the pouring process becomes easier,and the spherical microstructure of AlSi7Mg alloy slurry can be prepared by the weak traveling-wave electromagnetic stirring.When the pouring temperature is 630°C,increasing the stirring power appropriately can result in better spherical primary α-Al grains,but if the stirring power is increased to a certain value(1.72 kW),the shape of primary α-Al grains does not obviously improve when the stirring power is continually increased.     

Al-5Ti-B和稀土Y复合添加对A356合金半固态凝固组织的影响

采用稀土Y及Al-5Ti-B中间合金对A356铝合金进行细化处理,并用低温浇注技术制备半固态坯料.研究了单独添加Al-5Ti-B和稀土Y以及两者复合添加时对A356铝合金半固态凝固组织的影响.研究结果表明,Al-5Ti-B和稀土Y对A356铝合金半固态初生相的形貌及尺寸均有不同程度的改善.将两者复合添加时,可显著提高合金中初生相的形貌及尺寸,得到细小、圆整且分布均匀的半固态组织,其添加量的最佳组合为0.02％的Ti与0.5％的Y.探讨了两者复合添加对合金凝固组织的细化机理.     

浇注温度和细化剂对半固态A356合金组织的影响

采用低温铸造和晶粒细化复合工艺制备A356合金半固态坯料,研究了浇注温度和细化剂(Al-5Ti-1B)添加量对半固态坯料组织的影响。结果表明,随着浇注温度从715℃降到635℃,α-Al晶粒形貌从树枝晶向蔷薇状形态再到等轴晶组织变化,浇注温度越低,晶粒越细小圆整。当浇注温度降到615℃时,晶粒开始出现粗化和不均匀。在相同温度下,随着晶粒细化剂添加量的增加,晶粒更加细小,但细化效果随着添加量的增加变得不明显。当浇注温度低于635℃时添加细化剂,晶粒尺寸和形貌无明显变化。低过热度浇注和晶粒细化复合工艺制备A356合金半固态坯料的最佳工艺条件是:浇注温度为635~655℃,细化剂添加量为0.1%~0.2%。     

低过热度浇注SiC_p/Gr/ZL101复合材料组织与性能研究

采用半固态搅拌、低过热度重力浇注的方法制备了SiCp/Gr颗粒复合增强ZL101铝基复合材料。通过显微组织观察、拉伸试验以及阻尼性能测试,研究了不同体积分数SiCp/Gr对铝基复合材料性能的影响。结果表明,通过半固态搅拌、低过热度重力铸造法,使ZL101合金中的初生相α-Al由枝晶形态变为蔷薇状,晶粒明显细化。随着SiCp体积分数的增加,复合材料的抗拉强度先升高后降低,伸长率逐渐下降,复合材料的最高抗拉强度达到191MPa,比ZL101合金提高了32%。SiCp与Gr的加入改善了ZL101合金的阻尼性能,复合材料的内耗值Q-1明显高于基体合金,并且随着SiCp体积分数的增加,复合材料内耗值Q-1逐渐提高。     

离心激冷制备半固态铝合金

研究了离心激冷装置下半固态ZL203铝合金的制备,考察了不同的离心转速、外桶预热温度和浇注温度对合金初生相形态的影响规律.结果表明,采用离心激冷的方法可以制备出初生相为球状或细小颗粒状晶粒的半固态铝合金;随着离心转速提高,合金的初生相逐渐细化,其形态由等轴枝晶变成细小的球状或颗粒状晶粒;随着激冷桶预热温度和浇注温度降低,合金的初生相先细化,后有所粗化.     

Annulus electromagnetic stirring for preparing semisolid A357 aluminum alloy slurry

The effects of pouring temperature and annulus gap width on the microstructure of the semi-solid A357 aluminum alloy slurry prepared by annulus electromagnetic stirring(AEMS) technology were investigated. The results show that low pouring temperature and narrow annulus gap are advantageous to obtaining the small spherical primary α(Al) phase. The lower the pouring temperature is and the smaller the annulus gap width is, the more uniform, the smaller and the more spherical the microstructure is. The microstructures obtained by the ordinary electromagnetic stirring and AEMS were compared. The results indicate that the primary α(Al) particles are globular, small and distribute homogeneously in the slurry obtained by AEMS. But in the slurry obtained by the ordinary electromagnetic stirring, the primary α(Al) particles are small dendrites in the edge of the slurry and they are large and rosette-like or dendritic in the inner of the slurry.     

含铒A356合金半固态浆料的制备

采用添加稀土元素铒(Er)变质处理和弱电磁搅拌制备了A356合金的半固态成形浆料。利用微观组织观察、扫描电镜、透射电镜与能谱分析等手段,对制得试样的微观组织进行了研究,并对其形貌演变机理做了分析讨论。结果表明,微量(0.05%)Er元素添加到合金中,可使合金的初生α-Al晶粒从蔷薇花状变成细小的球状。在625℃时对含Er的合金液进行适当的弱电磁搅拌,可以进一步细化合金晶粒,制得半固态成形所需的浆料。     

半固态金属浆料先进制备技术的研究进展

总结了10多年来半固态金属浆料先进制备工艺的研究和应用现状,分别介绍了压室浆料、双螺旋机械搅拌浆料、低过热度倾斜板浇注浆料、低过热度浇注和弱机械搅拌浆料、连续流变转换浆料、低过热度浇注和弱电磁搅拌浆料、蛇形通道浇注浆料、熔体分散混合浆料、转桶搅拌浆料、波浪倾斜板浇注浆料、旋转倾斜圆筒浆料、超声振动浆料、倒锥形通道浇注浆料、自孕育浆料、偏旋热焓平衡浆料、气泡搅拌浆料、环状电磁搅拌浆料等金属浆料的先进制备工艺及其发展前景。     

阻尼冷却管法制备A356铝合金半固态浆料的研究

介绍了阻尼冷却管法制备A356铝合金半固态浆料工艺的试验装置及其工艺流程,在不同浇注温度下进行了系列试验,并与冷却斜槽法进行了对比分析。结果表明,浇注温度越低,浇注的铸件晶粒尺寸和形状因子数值就越小,晶粒球化程度越高。与冷却斜槽法相比,同一工艺参数下阻尼冷却管法制备的铸件晶粒更为细小和圆整。