钢铁半固态连铸成形技术的研究现状与展望

简要概述了半固态成形技术的基础理论研究，对钢铁半固态连铸的试验研究进行了分析，指出了钢铁半固态连铸工艺工业化的关键技术和努力方向。     

半固态铝合金设计与试验研究

在半固态加工的基本原理基础上采用合金热力学计算方法设计了Al-Si-Mg系半固态新合金，并进行了初步的试验验证。结果表明，新合金在铸态和半固态下的组织和力学性能特点与预测结果基本一致，并且发现适当增加Mg，si含量可以改善铝合金半固态加工性能和提高合金的力学性能。这对进一步开发新型的实用半固态合金具有一定的指导作用。     

金属的半固态加工技术

半固态金属加工是近年来金属加工技术研究的热点，本文在总结半固态加工技术特点的基础上，对半固态合金坯(浆)料的制备方法、半固态合金的成形技术以及近几年出现的一些新工艺和新方法进行了详细的论述。     

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。     

金属半固态铸造成形技术

金属的半固态铸造是近年来出现的一种新的铸造加工成形方法。该方法与传统的全液态铸造相比，具有节约能源、生产率高、产品质量好等优点。本文介绍了半固态金属浆料的制备方法，半固态压铸、半固态连铸等金属半固态铸造成形技术，并指出了存在的问题及进一步研究工作。     

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。     

汽车用铝合金零件的半固态触变压铸工艺研究

针对半固态触变压铸工艺特点，对国产J1128卧式冷室普通液态压铸机的压射系统和模具系统进行了结构改进．对压铸工艺参数进行了优化选择，并采用半固态专用铝合金AlSi6Mg2和商用铝合金A357开展了大量半固态触变压铸试验研究。结果显示，半固态触变压铸工艺与普通液态压铸有很大的不同，在压射室和模具预热温度分别为100℃和250℃、低压压力为4．0MPa、射料二速工作压力为12MPa、增压压力为20MPa、快压射速度为1．4m／s的条件下，可获得充型完好的汽车用铝合金半固态压铸零件。     

钢铁材料半固态坯料制备与成形的研究现状与展望

半固态成形技术是冶金材料领域重要研究课题。本文总结了半固态钢铁等高熔点材料制备与成形技术中的组织演变、坯料制备和成形工艺等方面理论与应用研究成果，对其发展现状与趋势进行了分析与讨论，并指出钢铁等高熔点材料半固态成形技术广阔的应用前景。     

半固态非枝晶组织合金的制备技术与应用

本文详细论述了半固态非枝晶组织合金制备技术的基本原理与特点，介绍了半固态非枝晶组织合金制备技术的现状与发展概况，并展望了半固态非枝晶组织合金的应用前景。     

稀土La对半固态A356初生相细化机制的研究

利用Al-La稀土中间合金对液态A356铝合金进行了细化处理,并用低过热度浇注技术制备了半固态A356铝合金浆料,研究了稀土La对所制备半固态A356铝合金的初生α相形貌和尺寸的影响.研究结果表明,含有适量稀土La的A356铝合金经低过热度浇注可制备具有颗粒状和蔷薇状初生α相的半固态浆料,稀土La可显著改善半固态A356铝合金中初生α相的晶粒尺寸和颗粒形貌.稀土La对半固态A356铝合金的初生α相细化机理可能与稀土在铝合金中诱发的共晶反应有关.     

微量Ce对细化A356合金初生相的作用

利用低过热度浇注技术制备了半固态A356-Ce合金浆料,研究了稀土Ce对半固态A356合金的初生相形貌和尺寸的影响.研究结果表明:含有适量稀土Ce的A356铝合金经低过热度浇注可制备具有颗粒状和蔷薇状初生相的半固态浆料,合金熔体等温温度会影响Ce细化半固态A356合金中初生相的效果.Ce对半固态A356铝合金的初生相细化机理与稀土在铝合金中诱发的共晶反应有关.      

立弯式浇道对半固态A356铝合金浆料组织的影响

采用立弯式浇道制备A356铝合金半固态浆料,研究了浇注温度对A356铝合金半固态浆料组织的影响,并考察了浆料经过均热处理后的组织。结果表明,采用立弯式浇道可以制备出半固态浆料,在本实验条件下,获得理想的半固态A356铝合金浆料的浇注温度为630℃和640℃,而且随着浇注温度的降低,初生相的形态由树枝状→蔷薇状→颗粒状转变;经过感应均热后,初生相更圆整,且尺寸、分布都很均匀。     

Microstructure and rheological properties of a semisolid A356 alloy with erbium addition

The effects of erbium addition on the rheological properties and microstructure of a semisolid A356 alloy were studied. The semisolid slurries were prepared through the serpentine channel technique before they were thixoformed using parallel-plate compression with cylindrical discs. The grain and globule size decreases as the Er content increases, resulting in an improved and uniform distribution of spherical primary α-Al phase within the semisolid slurry. The addition of the Er modifies the grain morphology and size of the α-Al grains, resulting in a better and more uniform distribution of spherical primary α-Al phase within the semisolid slurry. As a result, rheocast quality index increases with the addition of Er, which is suitable for the thixoforming process. The A356 alloy without Er has the highest viscosity herein. The viscosity decreases, and the flow characteristics of the semisolid feedstock are expected to improve when Er is added as a result of the refinement of primary α-Al and modification of eutectic silicon. Furthermore, the refined semisolid A356 alloys with Er show a slightly larger fraction of high-angle grain boundaries compared to that for the unre?ned alloy.     

Study on Rheological Behavior of Semisolid A356 Alloy During Solidification

In the present work, a model is developed to predict the rheological behavior of an Al-alloy (A356) in semisolid state where the alloy is sheared between two parallel plates during continuous cooling. The flow field is represented by the momentum conservation equation where the non-Newtonian behavior of the semisolid alloy is incorporated considering the Herschel?CBulkley model. In the slurry, the agglomeration and de-agglomeration phenomena of the suspended particles under shear are represented using a time dependent structural parameter. The temperature field during cooling is predicted considering the transient energy conservation equation, and hence the fraction of solid and the yield stress of the semisolid alloy are continuously updated. Considering an apparent viscosity of the semisolid alloy as a function of structural parameter, shear stress and shear rate, the governing equations are solved analytically. Finally, the work predicts the variation of the apparent viscosity of the semisolid A356 alloy with fraction of solid. At first, the present prediction is validated against an available experimental data and, thereafter, the work predicts the effect of process parameters such as shear rate and cooling rate on the apparent viscosity.     

Mechanical Behavior of AA6061 Aluminum in the Semisolid State Obtained by Partial Melting and Partial Solidification

The tensile properties of a 6061 aluminum alloy have been studied in the semisolid state at large solid fractions. The tests have been carried out either after a partial melting treatment or after partial solidification. Results show the following: (1) the mechanical behavior depends on the liquid-phase distribution and, therefore, on the way the semisolid state has been achieved (melting or solidification); (2) there is a critical solid fraction range where the semisolid alloy is relatively brittle; and (3) the mushy alloy exhibits viscoplastic behavior with the occurrence of micro-superplasticity at low strain rate. Modeling of this behavior is carried out by considering either the area fraction of grain boundaries wetted by the liquid or a cohesion parameter of the solid phase, which depends on solid fraction and thermal treatment.     

半固态铝合金的制备工艺研究

采用自制的电磁搅拌装置，制备出具有球形初生相微粒的半固态Ａｌ６．６％Ｓｉ合金。研究了冷却速率和搅拌强度对半固态合金的球形初生相微粒形成的影响。球形初生相颗粒的生成必须具有适当的冷却速率，而高的磁感应强度则有利于初生相颗粒的细化、球化和均匀化。提出了球形初生相微粒演化机理，认为剧烈的搅拌使初生相在长大过程中，不断发生枝晶臂的弯曲融合、熔断和机械断裂。     

Microstructural and Statistical Study of Semisolid Casting of 6061 Alloy Using a Miniature Cooling Slope

Preparation of metallic semisolid slurries using the cooling slope method is increasingly becoming popular because of the simplicity of design and control of the process. Microstructural features of the resultant semisolid castings such as size and sphericity of the primary particles are affected by several processing parameters such as pouring rate, cooling slope surface angle and length as well as the melt superheat. In this work, a miniature cooling slope for semisolid casting of small parts was built and attempts were made to develop an empirical relationship showing the correlation between the sphericity of the microstructure of semisolid cast 6061-aluminum alloy and the processing variables. The relationships were developed by a two-level factorial method. The results showed that the interaction of cooling slope length and pouring rate factors had the most effect on the sphericity of the final semisolid cast microstructure.     

AM60B镁合金等温热处理过程中的组织演变

借助于液淬技术、光学显微镜和电子显微镜,考察了等温热处理技术制备AM60B镁合金非枝晶锭料的可能性,研究了AM60B镁合金的微观组织演变。结果表明:AM60B镁合金铸件经过620℃×60min半固态等温热处理后,枝晶状的铸态组织变成圆整的球状半固态组织;半固态等温热处理过程中非枝晶组织的形成主要是由于原子扩散和能量起伏等原因造成。     

Rapid compression of aluminum alloys and its relationship to thixoformability

Shaping of metals by thixoforming relies on the unusual flow behavior of semisolid slurries containing nondendritic solid phase. The microstructure of an alloy stirred during freezing consists of rounded particles of solid, as opposed to the dendrites associated with conventional solidification. In the semisolid state, these slurries are thixotropic, in that their apparent viscosity is dependent on shear rate and time. Here, a technique of rapid compression testing is outlined, carried out under conditions similar to normal industrial thixoforming, to assess slurry flow behavior and to examine the correlation between feedstock production routes, microstructure, and resistance to flow. Samples are heated to the desired temperature in the semisolid state with various soaking times and rammed at constant velocity against a platen backed by a load cell. The load-displacement curves produced from the tests may show an initial peak, believed to originate from a skeletal structure which rapidly breaks down under shear. The load signal during flow decreases with increasing soaking time and with temperature, and the initial peak eventually disappears in all alloys investigated. Quantitative metallography indicates that the lower loads correspond to greater spheroidicity of the solid particles within the slurry. The curves have been analyzed to derive the viscosity as a function of average shear rate and demonstrate that the semisolid slurries exhibit pseudoplastic flow behavior which is dependent on the compression velocity and is far removed from steady-state conditions.