扬州大学成功研制新型稀土铝合金连杆

近日,扬州大学机械工程学院研究生刘韬带领的科研小组,在陈荣发教授的指导下,成功研制出新型的高强度半固态成型稀土铝合金连杆。这种新型的高强度半固态成型稀土铝合金连杆在铝合金成形过程中加入     

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。     

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。     

稀土在铝及铝合金中的应用现状与展望

稀土（RE）是十分活泼的金属。稀土元素作为微量元素加入铝合金中，可以净化合金熔体、减少夹杂．细化、变质微观组织；作为合金元素加入适量稀土可显著提高铝合金的综合性能。本文讨论了稀土在铝及铝合金中的作用机理，论述了稀土在铝及铝合金中的开发应用现状．展望了稀土铝合金的发展前景。     

半固态A356合金重熔加热时初生相的组织演变

利用低过热度浇注技术制备了半固态A356铝合金坯料,研究了半固态温度区间重熔加热时半固态A356铝合金坯料的初生相形貌的转变过程.结果表明,在半固态两相区保温,半固态A356合金的初生相逐渐团球化,该过程随保温温度的升高而加快.半固态A356铝合金晶粒的圆度与保温温度和保温时间的关系不大,但晶粒的尺寸随着保温温度和保温时间的增加而增大.半固态A356合金试样重熔加热最佳工艺制度为583℃下保温30min,其晶粒平均等积圆直径为80μm,晶粒平均圆度为0.83.     

浇注温度对合金熔体冷却规律和半固态组织的影响

介绍了一种实验室自主研发的轻合金半固态浆料制备设备——锥桶式流变成形机(TBR),该设备利用刻有凸纹和沟槽的内、外锥桶的相对转动,使合金熔体在凝固过程中受到剧烈的剪切搅拌,从而获得合金半固态浆料.对TBR工艺的传热模型进行了推导,以A356为实验材料得出制备的A356铝合金半固态浆料温度与浇注温度的关系式,同时分析了不同浇注温度下合金熔体的冷却规律和获得的半固态组织形貌.结果表明,适当降低A356合金熔体的浇注温度可以延长初生固相受到的剪切时间和增加剪切次数,从而获得细小、均匀的半固态组织.当浇注温度为640℃时,初生固相平均晶粒尺寸为68μm,形状因子为0.82.     

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.     

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。     

铝合金半固态触变模锻成形过程流动充型模拟

设计了铝合金半固态模锻标准拉伸试样模具,采用一模五件。选用典型锻造铝合金7075作为材料,用Deform软件进行模拟分析,分别进行流动充型试验,对比分析不同的充型结果。确定合理的坯料尺寸、放置方式及半固态温度为:60×120mm,垂直放置,580℃。选用7050合金进行实际半固态模锻成形,制备了拉伸试样零件,结果表明,本模具设计合理,充型流动模拟优化方法合理可靠。     

稀土在铝和铝合金中应用的研究及进展

稀土元素作为微量元素加入铝及其合金中,不仅有细化晶粒的变质作用,还有净化熔体、减少气体含量及氧化夹杂的精炼效果,从而可显著改善和提高铝及其合金的综合性能.分析讨论了稀土在铝及铝合金中的作用,论述了稀土在铝及铝合金中的开发应用现状,展望了稀土铝合金的发展前景.     

Influence of the Magnetic Field on the Crystallization of Aluminum Melts

In order to control the crystallization of metals consciously with the purpose of forming the specified ingot microstructure, various physical fields are used. They vary the internal state of the melt and, consequently, the crystallization kinetics when affecting the melt. In this article, the thermodynamic and kinetics of the crystallization of aluminum under melt processing with the magnetic field is described. A rather simple experimental setup which makes it possible to investigate the magnetic-field effect on the melts of aluminum or other metals and alloys is designed. It consists of several main units: (1) the electrical furnace, (2) the water-cooled copper crystallizer combined with an electromagnetic coil, (3) mechanical facility for the rapid motion of a crucible with the aluminum melt, (4) the monitoring and control system of the melt temperature, and (5) the electronic part for recording and processing information. It is established experimentally that the magnetic field varies the temperature of the melt–crystal phase equilibrium, latent heat of the phase transition, and supercooling temperature of the melt during crystallization. It is shown that the variation in these parameters leads to a decrease in the radius of critical nuclei and an increase in their nucleation rate. The temperature–temporal dependences of crystallization are found. It is established experimentally that the crystallization time shortens under the aluminum melt treatment with the magnetic field. The analysis of aluminum samples formed under the magnetic-field effect showed that their structure is finer grained when compared with the samples not subjected to such treatment.     

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。     

Thixoforming of A356/SiC and A356/TiB2 Nanocomposites Fabricated by a Combination of Green Compact Nanoparticle Incorporation and Ultrasonic Treatment of the Melted Compact

Thixoforming is a type of semi-solid processing which is based on forming metals in the semi-solid state rather than fully liquid or solid state. There have been no reports of the thixoforming of nanocomposites in the literature. The incorporation of ceramic nanoparticles into liquid metals is a challenging task for the fabrication of metal matrix nanocomposites due to their large surface-to-volume ratio and poor wettability. Previous research work by a number of workers has highlighted the challenges with the incorporation of nanoparticles into liquid aluminum alloy. In the present study, SiC and TiB₂ nanoparticles with an average diameter between 20 and 30 nm were firstly incorporated into green compacts by a powder forming route, and then the compacts were melted and treated ultrasonically. The microstructural studies reveal that the engulfment and relatively effective distribution of the nanoparticles into the melt were achieved. The hardness was considerably improved with only 0.8 wt pct addition of the nanoparticles. The nanocomposites were successfully thixoformed at a solid fraction between 0.65 and 0.70. The microstructures, hardness, and tensile mechanical properties of the thixoformed nanocomposites were investigated and compared with those of the as-received A356 and thixoformed A356 alloys. The tensile properties of the thixoformed nanocomposites were significantly enhanced compared to thixoformed A356 alloy without reinforcement, indicating the strengthening effects of the nanoparticles.     

Characterization of Flow Behavior of Semi-Solid Slurries with Low Solid Fractions

Semi-solid slurry casting is a metal-forming process that involves transforming liquid metal into slurry having a low solid fraction and then forming the slurry into solid parts. To successfully apply this slurry-forming process, it is necessary to fully understand the flow behavior of semi-solid slurries. This present work applied the rapid quenching method and the modified gravity fluidity casting to investigate the flow behavior, which involves characterizations of the initial solid fraction, fluidity, and microstructure of semi-solid slurries. Three commercial aluminum alloys were used in this study: 383 (Al-Si11Cu), 356 (Al-Si7MgFe), and 7075 (Al-Zn6MgCu) alloys. The results show that the initial solid fractions can be controlled by varying the rheocasting time. The rapid quenching mold can be used to determine the initial solid fractions. In this method, it is important to apply the correcting procedure to account for growth during quenching and to include all the solid phases. Results from the fluidity study of semi-solid slurries show that the fluidity decreases as the initial solid fraction increases. The decrease is relatively rapid near the low end of the initial solid fraction curves, but is quite slow near the high end of the curves. All the three alloys follow this trend. The results also demonstrate that the slurries that contain high solid fractions of up to 30 pct can still flow well. The microstructure characterization results show that the solid particles in the slurries flow uniformly in the channel. A uniform and fine microstructure with limited phase segregation is observed in the slurry cast samples.     

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.     

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。     

Mg-Al系镁合金半固态组织二次凝固特征

半固态浆料液相的凝固行为决定了其二次凝固组织,这将直接影响半固态成形件的性能.Mg-Al系镁合金随着成分、凝固行为的不同,其二次凝固组织有较大的不同.该文描述了Mg-Al系合金半固态浆料液相凝固过程以及二次凝固组织特征,并针对其特征对其形成原因展开了分析.     

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。