半固态金属的流变行为述评

叙述了半固态金属的流变学理论，常规铸造组织和半固态金属的流变行为，固相体积分数，剪切速率，冷却速度等因素对半固态金属表观粘度的影响，以及半固态成形技术的研究现状，以期推动半固态流变理论的研究和半固态加工技术的实际应用。     

半固态铸造技术研究现状与展望

半固态铸造是一种新的材料成形技术，综述了半固态铸造合金的组织变化，坯料制备，充型过程数值模拟和应用等方面的研究成果，同时对我国发展半固态铸造技术得出了若干值得重视的问题。     

半固态加工技术的进展及我国应对措施

半固态金属成形技术具有高效、节能、近终形生产和成形件性能高等许多优点，被专家们称为21世纪最具前景的加工方法。本文介绍了半固态金属成形的成形工艺、坯料制备工艺、微观组织、数值模拟状况及国内外研究应用情况，展望了半固态金属 的前景，提出了我国的应对措施，     

半固态304型不锈钢凝固和重熔过程中的结构形态及形变特征

1前言 半固态金属成形主要用于对铝合金和镁合金等轻金属的加工。到目前为止，半固态金属成形一直被用来制造此类合金的各种金属部件，如汽车和移动电话的配件。对于轻金属半固态成形的绝大多数研究的目的是为了揭示轻金属合金半固态成形实用技术发展的基本特征。相比之下，对包括不锈钢在内的铁基合金半固态成形的研究还非常少，这可能是由于此类合金具有较高的熔点、较窄的半固态温度区间以及在凝固和重熔过程中发生复杂的γ←→δ相变。对铁基合金半固态成形工艺进行优化需要了解其在半固态时的材料特性。这些特性在半固态温度区间内受到材料显微结构变化的显著影响。对于铁基合金半固态成形的研究仍处于基础阶段。     

国外半固态合金及复合材料成形技术发展概述

据美国国家研究委员会最近提出,半固态合金及复合材料成形技术,经过近20多年的研究和发展,到目前已逐步开始进入工业应用阶段,即将成为对21世纪的制造工业产生重要影响的新兴制造工艺。 半固态金属成形技术是随着搅动铸造     

金属半固态加工技术及其在工业中的应用

半固态金属加工是近年来金属加工技术研究的热点，因为它具有一系列优点，最突出的是半固态材料的触变性，成形的零件精度高、质量好，能与净近成形或净终成形（Near-net-shape）接轨。本文详细阐述了半固态金属成形特点和半固态金属制品的力学特性，同时还介绍了半固态技术在工业中的应用。     

半固态加工技术的进展、前景及对策

半固态金属成形技术具有高效,节能,近终形生产和成形件性能高等许多优点,被专家们称为21世纪最具前景的加工方法,介绍了半固态金属成形的成形工艺,坯料制备工艺,微观组织,数值模拟状况,国内外研究应用情况,展望了半固态金属的前景,并提出了应对措施。     

半固态金属加工技术

半固态加工技术是一种新的材料成形技术。作者综述了半固态金属的成形工艺、坯料制备工艺、微观组织、国内外研究应用情况，展望了半固态金属加工技术的前景，并提出了应对措施。     

钢铁半固态成形技术的研究进展和展望

低熔点合金半固态成形技术被专家称为21世纪新兴的金属制造关键技术。该技术已经成功地在商业领域中运行，人们一直在探索将此技术应用于钢铁材料。本文综述了钢铁半固态成形技术的研究开发过程，介绍了钢铁半固态成形的工艺、浆料的制备方法、半固态金属的微观组织演变以及对这种成形工艺的展望。笔者认为电磁搅拌制备浆料方法中的搅拌是无接触搅拌，更适用于高熔点钢铁材料。由于触变成形工艺本身的特点，使其更适宜于钢铁等高熔点材料的半固态成形控制。     

半固态金属成形技术及应用

半固态金属加工是近年来金属加工技术研究的热点。本文论述了半固态金属坯料制备、成形方法、微观组织及其数值模拟，并阐述了其发展应用和前景。     

Research and Applications of Semi-solid Processing

It has been more than ten years since the semi-solid processing (SSP) technique was put into commercial ap plications in the world. A lot of work on semi-solid metals (SSM) including their preparation, reheating and semi-solid forming has been done in China. In order to produce the high quality die-casting, a novel innovation that modifies the present machines based on the SSP technique was proposed. Semi-solid die-casting on modified casting machines can manufacture parts with more excellent quality than those produced by squeeze casting. It was found that the defects such as "elephant foot" and "periphery liquid metal loss" during reheating could be avoided through controlling the non-de ndritic structure of billets and optimizing the reheating process. The processing parameters and mold designs of semi-so lid die-casting are fairly different from those of liquid die-casting.     

稀土铝合金结晶过程的研究

半固态成型正在成为有色金属成型的一种新技术.目前大部分铝合金是为了满足液态成型或塑性成型的特性而设计的,难以较好地满足半固态成型的特性要求,因此,设计出新的铝合金以满足半固态成型要求就十分必要.为此,本文讨论了稀土元素对铝结晶过程的影响.实验结果表明:在纯铝中加入稀土元素后,不但使合金的结晶温度区间加宽,而且使合金的结晶时间延长,这样将有利于半固态成型技术的实现.     

半固态浆料制备技术发展动向及其对策

以半固态金属流变成型技术为依托，论述了半固态浆料的质量要求和浆料制备新工艺，并针对浆料制备的关键技术(半固态浆料制备工艺和设备、新型材料设计和等轴非枝晶的形成机理)提出了建议性对策。     

Grain Boundary Characteristics of As-cast Semi-solid Processed Ultra-high Carbon Steel

The microstructure of 1.4?% carbon steel produced either by ordinary casting or semi-solid casting with different primary fraction of solids using cooling plate technique was investigated. The microstructure of ordinary ultrahigh-carbon steel (O-UHCS), was improved by the semi-solid processing. Grain boundary cementite thickness of UHCS and its morphology is affected by semi-solid process. Grain boundary cementite thickness of about 2???m can be achieved by pouring the semi-solid slurry with 0.31 fraction of solid. The pearlitic interlamellar spacing of semi-solid processed UHCS is shorter compared to O-UHCS.     

New aspects of the plastic deformation of light alloys in the thixotropic state

Conclusions Ultrasonic (cavitational) treatment of the melt during continuous casting makes it possible to form a limitingly fine nondendritic structure, which opens up new possibilities for the process of semi-solid deformation. The deformation process is made easier and the treatment eliminates the need for the additional operation of converting the fine-grained dendritic structure of the ingot into a coarse nondendritic structure by heating the metal in the semi-solid state. The process can be used for the die-forging of complex parts made of high-strength structural aluminum alloys of the system Al-Zn-Mg-Cu-Zr. Russian Academy of Natural Sciences. Translated from Metallurg, No. 4, pp. 18–20, April, 1998.     

Simulation of Cooling of Liquid Metal in an Inclined Slope to Predict the Condition for Semi Solid Forming and Its Experimental Validation

In semi solid processing, the preparation of slurry with globular microstructure is very important. A recent technique named the inclined slope casting, to produce the semi-solid metal slurry, has been evolved. The microstructure of casting depends on several process parameters like initial temperature of liquid metal, length of the slope, cooling rate and the rate of flow of liquid metal. In the present work numerical modelling of cooling of liquid was carried out. Modelling was done for different mass influx velocities, temperature of pouring and different inclinations of the slope set-up. In this work, a CFD model based on finite volume method for simulating flow along the inclined slope was carried out. Heat transfer, fluid flow and solidification were studied by varying the process parameters like slope angle and inlet pouring rate. The numerical results were verified with experiments for same conditions.     

Influence of Procedure Parameters on Rheological Property of Semi-Solid AZ91D Magnesium Alloy

Semi-solid AZ91D magnesium alloy was investigated in isothermal steady-state condition. The influence of stirring technological parameters such as stirring temperature and shear rate to apparent viscosity of semi-solid alloy slurry was discussed. Apparent viscosity increases with stirring temperature decreases at the same shear rate. At the same stirring temperature, apparent viscosity decreases rapidly at first with shear rate increases, and then apparent viscosity decreases slowly with shear rate increases, when shear rate reaches a certain value, apparent viscosity appears tiny increase. According to the experimental data, the relation between solid volume fraction and apparent viscosity of semi-solid AZ9l D alloy at shear rate 238 s- 1 is fitted by regression method, it supplies useful data to the numerical simulation of semi-solid AZ91D alloy die casting process.     

Investigation of spherisation in microstructures of aluminium casting alloys for thixoforging process

Thixoforging combined with low superheat casting (LSC) is a promising shaping process for aluminium casting alloys. LSC process is based on rapid solidification of an alloy which cast with low pouring temperature. With this method, a feedstock material is produced with non-dendritic microstructure that ready for spherisation in reheating sequence of further semi-solid process. Al-Si alloys are still castable even at low temperatures due to their excellent fluidities. This study subjects to present spherisation of A356 and A380 alloy billets cast with LSC process that provides appropriate beginning material with relatively high sphericity. Obtained billet parts were reheated for different times at a semi-solid state temperature. Some of these billets were directly quenched for observing the effects of reheating and the others were thixoforged. With sufficient reheating time, deformation of thixoforging process did not significantly affect on the spherical microstructure. Unnecessarily long reheating period caused excessive grain growth. A356 alloy had higher spherisation tendency than A380 alloy under similar process conditions.