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。     

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。     

近液相线半连续铸造法制备半固态铝合金的研究进展

介绍半固态铝合金的各种制备工艺，分析了近液相线半连续铸造法制备半固态铝合金的现状与发展趋势，探讨半固态初生球状晶形成机理的研究现状，指出近液相线半连续铸造法具有广阔的应用前景。     

半固态金属加工工艺过程的模拟进展

论述了半固态金属加工技术,即流变铸造,二次加热与触变成形等工艺过程数值模拟技术的研究进展和现状,给出了各工艺过程的模拟实例,并对半固态金属加工过程模拟的发展进行了评价。     

带有晶粒细化剂的铝合金半固态铸造工艺

美国专利US7025113本方法是把钛基晶粒细化剂混合入亚共晶铝硅合金半固态浆料中,用以细化半固态浆料中的初晶铝。所涉及的专利工艺是把钛硼合金与亚共晶铝硅合金液混合,在半固态铸造中控制初晶铝相的形态尺寸和分布。本发明能使晶粒细化技术很好地应用于铝硅亚共晶合金的半固态铸造。     

半固态锌基复合材料摩擦特性研究

采用流变成型法制备了半固态ZA27—16Vol％Si合金，与常规铸造合金进行了对比，并对其摩擦特性进行了研究，为锌铝合金的半固态加工新技术提供了理论依据。     

基于铸造软件的发动机外壳件铸造过程的模拟

铸造铝合金在汽车、摩托车零件中广泛应用,但传统铸造方法铸造时间长,铸造缺陷多,已无法满足产品质量的稳定要求。半固态铸造作为一种新型铸造工艺,已逐渐得到行业和企业的重视。本文以铸造CAE软件的数值模拟方法作为研究手段,对摩托车发动机外壳件进行半固态铸造成形过程的有限元模拟。通过FLOW-3D铸造软件在液态和半固态情况下的模拟仿真,得到不同条件下的充型和浆料流动特点,获取合理的模拟凝固时间和保压时间。通过对比分析,得出相对优化的数值参数,为铸造企业进行相关的半固态铸造实验提供可参考的工艺参数。     

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     

7A04高强铝合金轮毂半固态锻造工艺在汽车制造中的应用

传统铝合金轮毂锻造工艺复杂,制件性能较低。传统锻造难以复杂的形状轮毂,且容易变形。半固态锻造工艺介于液态和固态两种形态锻造之间,完美融合优点,具有短流程、低成本、高性能等优势。为此,提出一种7A04高强铝合金轮毂半固态锻造工艺技术,该技术在较为复杂的铝合金轮毂一副模具内半固态流铸造和锻造一体化实现,完美融合了铸造和半固态成形等工艺,锻造过程短流程、出产轮毂快速高效、复杂零件力学性能高。仿真实验表明,提出的7A04高强铝合金轮毂半固态锻造工艺在汽车制造中应用,比传统方法锻造工艺用时更短,质量更高,具有广泛使用价值。     

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。     

稀土细化剂对半固态A356铝合金等温热处理组织的影响

利用低温浇注与晶粒细化法制备了半固态A356铝合金坯料,研究了在细化剂作用下等温热处理工艺条件对其组织的影响规律.研究结果表明,稀土细化剂的加入对试样等温热处理前的铸态组织和热处理后的加热组织都有明显的改善作用,且稀土细化及低温浇注共同作用时,所获得的半固态非枝晶A356铝合金试样等温热处理最佳工艺条件为583℃下保温30 min,此时坯料触变性良好,其晶粒平均圆度达到0.83,晶粒平均等积圆直径达到80μm.     

AlMg_5Si_2Mn铝合金等温热处理半固态成形工艺探索

铝合金等温半固态触变成形是一种先进的成形工艺理念,目前尚处于工程化应用前期。本文以AlMg_5Si_2Mn铝合金为研究对象,采用等温热处理法制备实验合金半固态浆料,并研究其半固态等温过程的组织演变规律。然后使用压铸设备开展AlMg_5Si_2Mn铝合金的半固态成形工艺试验,探索可行的半固态成形工艺和合理实现路径。     

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.     

铜镍合金化及半固态处理工艺对ZrCoAl系非晶合金组织的影响

向以Zr80Co15Al5为基体的非晶合金中添加微量铜和镍,利用铜模吸铸法和半固态处理工艺制备棒状(Zr0.88Cu0.12)95-2x Al5(NiCu)x(x=1.5、2.5、3.5)非晶合金。利用SEM、XRD和光学显微镜(OM)分析研究了半固态处理工艺对非晶合金的微观组织结构、玻璃形成能力及断口形貌的影响。结果表明,在半固态处理工艺基础上对Zr80Co15Al5添加微量铜和镍后有较好的晶体形成能力。     

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.     

Computational modelling of dendritic to globular transition using an isothermal binary phase-field model

Globular microstructure is suitable for high pressure die casting of semi-solid billets. This is achieved by means of mechanical deformation of the melt or by means of a forced convection in the presence of a thermal gradient. The morphological evolution in an alloy with the starting microstructure as predominantly dendritic is simulated using the phase-field technique. An attempt is made to study the effect of varied thermal profiles that are imposed on the solidified dendrite and the morphological changes effected there upon. Two dimensional simulations are performed for a dilute alloy of a simple lens type phase diagram and the results are presented.     

Modeling of the Twin-Roll Casting Process: Transition from Casting to Rolling

During twin-roll casting, an alloy melt is passing the gap between two counter-rotating rolls, where cooling and solidification leads to the continuous formation of a solid strand. In order to describe this process, a two-phase Eulerian–Eulerian volume-averaging model is presented that accounts for (1) transport and growth of spherical grains within a flowing melt, (2) the formation of a coherent solid network above a specific solid fraction and (3) the viscoplastic flow of the solid network with the interstitial melt during casting and compression. For the considered case of an inoculated Al–4wt%Cu alloy, the process conditions are chosen such that two relatively thick viscoplastic semi-solid shells meet between the rolls, and thus, the material is pressed together and squeezed against the casting direction. The squeezed out material consists of segregated melt and some solid that quickly disappears after melting. It is observed during this study that macrosegregation distributions are inherently connected to the mush deformation that is enforced during the hot rolling process.     

Effect of lanthanum addition on microstructure and hardness of brass alloys produced by rheological squeeze casting

The effect of La addition (0–0.30 wt%) on the microstructure and hardness of rheological squeeze casting brass alloys was experimentally investigated. The rheological squeeze casting process is improved by controlling the wall surface crystals and melt flow rate to realise the preparation of semi-solid melt with flow, and a brass alloy workpiece with La is produced. The microstructure and properties of the brass alloy samples were investigated using metallography, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and hardness testing. The results indicate that the hardness of the rheological squeeze casting brass alloy is increased by 20.4% from 108 to 130 HBW with an increase in the La content from 0 to 0.30 wt%. The microstructural analysis results show that La significantly refines the primary α-phase grains, and the main mechanism is the constitutional undercooling and heterogeneous nucleation caused by the La enrichment in the front of the solid–liquid interface. The squeeze pressure promotes undercooling, which improves the nucleation rate and affects the solute diffusion and nucleus growth. The dual effects of these two aspects aggravate the grain refinement process, consequently increasing the number of grain boundaries and improving the hardness of the brass alloy.     

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.