SiC_p/2024铝合金复合材料粉末混合半固态挤压法制备

研究了SiCp/ 2 0 2 4铝合金复合材料的粉末混合 半固态挤压成形工艺及所制备材料的组织和界面特征。不同温度下半固态挤压的挤压力与位移曲线表明 ,半固态挤压过程的成形力低且稳定。SEM和TEM电镜观察结果表明 ,该工艺可以获得增强颗粒分布均匀、基体组织致密、界面结合良好且无界面反应的复合材料型材。分析了半固态挤压后复合材料的力学性能 ,结果表明 :与基体合金相比 ,复合材料的弹性模量、屈服强度、抗拉强度均有很大提高 ;与其它工艺生产的该复合材料相比 ,所制备的复合材料的塑性相对较高。     

半固态制备Ti_3SiC_2/Al-4Si复合材料的界面反应对组织及性能影响

以Ti_3SiC_2粉末为增强体,Al-4Si合金作为基体,通过半固态工艺制备了5%(质量分数)Ti_3SiC_2/Al-4Si复合材料。利用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)等研究了半固态制备5%(质量分数)Ti_3SiC_2/Al-4Si复合材料的界面反应对其组织及性能的影响。结果表明,在半固态制备过程中Ti_3SiC_2与Al-4Si基体发生界面反应生成了Al_3Ti、TiC、Al_4C_3物相,Al_3Ti及TiC颗粒分布在晶界处;复合材料硬度约为46.8 HV0.3,相比Al-4Si基体合金硬度略微提高;与Al-4Si基体合金相比,界面反应产生的第二相颗粒显著改善复合材料的摩擦学性能,摩擦系数为0.263,磨损量为0.0069 g。     

触变成形亚/过共晶铝-硅双金属复合材料性能研究

通过应变诱发熔化激活(SIMA)半固态触变模锻技术,制备了亚/过共晶铝-硅合金双金属复合铸造制品,其中亚共晶合金为Al-7Si合金,过共晶合金为Al-20Si合金。运用金相显微(OM)和电子扫描显微(SEM)技术对双金属复合材料界面组织和界面处的缺陷进行了分析;运用拉伸试验机对复合材料界面的结合性能进行了检测和分析。结果表明,界面处组织在压力的作用下相互融合均匀,界面处存在少量气孔、夹杂;室温拉伸试样都在过共晶Al-20Si合金一侧断裂,界面保持良好,其抗拉强度为113 N/mm2。经过计算,复合界面的结合强度大于80 N/mm2,该界面达到冶金结合。     

半固态合金加工技术的新探索

在"我国第一届半固态金属加工技术研讨会"和"第6届国际合金及复合材料的半固态加工学术会议"的学术论文中,对发展半固态合金加工技术提出一些值得注意的、富有挑战性的技术见解.作者对其中的控制冷却和采用新材料进行了初步探索.     

SiCp/ZL102复合材料的半固态流动变形性能

对颗粒增强铝基复合材料进行压力铸造工艺加工 ,是解决颗粒增强铝基复合材料近终成形的一种新方法。在模拟压铸充型的条件下 ,研究了SiCp/ZL10 2复合材料的半固态流动变形性能。结果表明 ,在相同的实验条件下 ,复合材料的半固态流动变形性能比基体合金优越 ,且在SiC颗粒体积分数低于 12 %的条件下 ,SiC颗粒越多 ,材料的半固态流动变形性能越好。此外 ,随保温温度的提高、保温时间和重锤高度的增加 ,复合材料和基体合金的半固态流动变形性能都有所提高。     

半固态合金加工技术若干问题的思考

在第一届半固态金属加工技术研讨会和第6届国际合金及复合材料的半固态加工学术会议的学术论文中,对发展半固态合金加工技术提出一些值得注意的、富有挑战性的技术见解,例如控制冷却的制浆技术、连续加热的加热-部分重熔技术、新型半固态合金的研制、成形与凝固分离、等温-密实-冷锻-密实-终成形、加工过程的集成和一体化等等,作者均给予了扼要介绍,并提出了发展我国半固态加工技术的前景对策。     

SiC_p/ZA27复合材料在半固态等温热处理中的组织演变

研究了 Zr变质处理的 Si Cp/ ZA2 7复合材料在半固态温度保温过程中的组织演变情况 ,并与基体合金作了对比。结果表明 :经 0 .6 % Zr处理的 Si Cp/ ZA2 7复合材料在 46 0℃保温 30～ 40 min可获得良好的半固态触变成形所需的组织 ;复合材料的组织演变速率比基体合金的快 ,且在长时间保温 (>40 min)时 ,其组织的粗化现象不如基体合金明显     

半固态成形技术最新进展——第11届合金与复合材料半固态成形国际会议技术报告综述

两年一次的合金与复合材料半固态成形国际会议是半固态成形领域内水平最高的学术会议.第11届合金与复合材料半固态成形国际会议于2010年9月16-18日在北京召开.会议发表的技术报告,内容涉及材料开发及合金设计,组织及性能,流变行为、模型及数值模拟,工艺开发,工业应用等.     

SiC颗粒、保温时间对SiC_P/AZ61复合材料半固态组织的影响

研究SiC颗粒、保温时间对SiCP/AZ61复合材料半固态组织的影响,并探讨复合材料等温过程中半固态组织演变机理。结果表明,SiCP/AZ61复合材料在温度595℃,不同保温时间(0min～90min)下,其组织的演变过程为,枝晶臂合并→大块状组织→晶界处局部熔化分离→晶粒组织球化→球状组织缓慢长大。在温度595℃,保温30min～60min时,SiCP/AZ61复合材料可以获得最佳的半固态组织;与AZ61基体合金相比,由于SiC颗粒的加入,使得SiCP/AZ61复合材料在等温热处理过程中的半固态组织更为细小,并且随着SiC颗粒体积分数增加,其半固态组织中球状颗粒的尺寸越小。     

SiCp／ZA27复合材料在半固态等温热处理中的组织演变

研究了Zr变质处理的SiCp／ZA27复合材料在半固态温度保温过程中的组织演变情况,并与基体合金作了对比。结果表明：经0．6％Zr处理SiCp/ZA27复合材料在460℃保温30－40min可获得良好的半固态成形所需的组织;复合材料的组织演变速率比基体合金的快,且在长时间保温（＞40min）时,其组织的粗化现象不如基体合金明显。     

A2017合金半固态压缩变形力学特性

采用Gleeble 15 0 0热模拟机 ,对SCR (shearing/coolingroll)技术制备的A2 0 17半固态合金和常规铸造A2 0 17合金在不同变形温度和不同变形速率下进行半固态压缩实验 ,研究了A2 0 17合金半固态压缩变形的力学特性。实验结果表明 ,相同变形温度下 ,SCR技术制备的A2 0 17半固态合金半固态压缩变形抗力低于常规铸造A2 0 17合金半固态压缩变形抗力 ,这主要是SCR技术制备的A2 0 17半固态合金具有的均匀的近球形晶和共晶液相组成的组织优于常规铸造的枝晶组织 ,其压缩变形机制不同于常规铸造枝晶的压缩变形机制。实验结果还表明 ,SCR技术制备的A2 0 17半固态合金半固态压缩变形抗力 ,对压缩变形温度和变形速率具有敏感性 ,随着变形温度降低或者变形速率升高 ,变形抗力增加。     

Synchrotron Radiography Studies of Shear-Induced Dilation in Semisolid Al Alloys and Steels

An improved understanding of the response of solidifying microstructures to load is required to further minimize casting defects and optimize casting processes. This article overviews synchrotron radiography studies that directly measure the micromechanics of semisolid alloy deformation in a thin-sample direct-shear cell. It is shown that shear-induced dilation (also known as Reynolds’ dilatancy) occurs in semisolid alloys with morphologies ranging from equiaxed-dendritic to globular, at solid fractions from the dendrite coherency point to ~90% solid, and it occurs in both Al alloys and carbon steels. Discrete-element method simulations that treat solidifying microstructures as granular materials are then used to explore the origins of dilatancy in semisolid alloys.     

铝含量对应变诱发法半固态镁合金的影响

结合半固态合金成分设计原则,通过热力学计算,研究了3种成分的半固态镁合金。通过组织观察和流变学参数分析表明,半固态组织的形成速度随铝含量增加而加快,固相粒子变得细小、圆整。分析得出铝元素主要通过两个方面影响半固态组织,一个是液相形核,另一个是再结晶晶粒尺寸。随着铝含量增加,液相形核数量增多,再结晶晶粒尺寸减小,这些都促进了半固态组织的形成和演变,有利于镁合金半固态加工。     

Controlled Nucleation Method:A New Process for Semisolid Metal Forming

Semisolid metal forming requires special feedstock material with a fine-grained and globular structure to achieve thixotropic properties. A number of methods have been developed to produce such feedstock materials. Controlled Nucleation Method (CNM) is a new and simple, cost effective method that has been developed by the University of Queensland. The CNM process does not use the conventional stirring process, instead, it uses solidification conditions to control nucleation, nuclei survival and grain growth, thereby produce fine and globular structures suitable for semisolid forming. No specialised equipment is required. The method can produce both semisolid slurry for rheocasting and semisolid billet for thixocasting. It can be applied to a wide range of alloys and can easily be incorporated into existing metal forming installation. Semisolid slurries/billets of hypoeutectic and hypereutectic aluminium-silicon casting alloys, aluminium wrought alloys and a magnesium alloys have been successfully produced.     

喷射沉积材料半固态成形的现状与发展前景

综述了喷射沉积材料的半固态成形的研究进展和发展趋势,分析了喷射沉积材料的半固态成形工艺、半固态变 形特征和半固态成形的加热和保温过程中组织演变规律,提出高固相率的触变成形是喷射沉积材料半固态成形的发展方 向。     

Site occupancy in ternary L12 ordered alloys as determined by diffraction: observations on (Al,Cr)3 Ti alloys

The nature and occurrence of point defects have been studied in L1₂ ordered (Al,Cr)₃Ti alloys. Four compositions were investigated, two stochiometric alloys with either 9 or 12 at. pct. Cr, and two nonstoichiometric alloys with 10 at. pct. Cr and either 23 or 27 at. pct. Ti. Measurements of lattice parameter, density, and composition were combined to calculate the average number of atoms per unit cell. No variation in this quantity was detected with alloy composition, suggesting that the dominant point defects in these ordered phases are antisite defects rather than constitutional vacancies. A lack of constitutional vacancies was further supported by comparisons of measured and calculated superlattice peak intensities. The common method of regression fitting calculated and measured X-ray diffraction intensities using a single wavelength is shown to be unable to define the two independent order parameters unambiguously, calling into question the results of such previous studies on these ternary alloys. Only if an assumption is made that one type of site substitution dominates the antisite formation can the method be used to estimate the solution for the dominant behavior. Assuming that one type of substitution dominates the antisite formation on β (Ti) sites, the measurements performed in this study suggest a small amount of Cr, but not Al, substitution on β sites, and that most of the Cr is on α (Al) sites. Increasing the Cr level in stoichiometric alloys causes more Cr to occupy β sites, displacing some Ti to α sites, thus creating more antisite defects. The Ti deficiency in hypostoichiometric alloys is alleviated by enhanced substitution of Cr on β sites. However, the excess Ti in hyperstoichiometric alloys greatly decreases any Cr substitution on β sites.     

An internal-variable constitutive model for semisolid slurries at high solid fractions

A mathematical model is proposed to represent the thixotropic behavior of semisolid slurries at high solid fractions (ƒ_s > 0.6), as occurs in dispersion-strengthened metal-matrix composite processing. The model assumes that the slurry behaves as a viscoplastic porous medium saturated with liquid phase and hardened or softened, depending on the shear rate and solid fraction. The model is validated by comparison of its predictions with a recent set of experimental data on Sn-Pb alloys.     

金属半固态加工

半固态加工是生产形状复杂的近终形产品的一种新方法。从半固态金属的基本物理性能,阐述了半固态金属浆液的制备、半固态金属的成形、半固态加工产品的机械性能、应用及未来发展趋势。     

半固态金属成形技术的研究概况

在合金凝固过程中加以搅拌或通过其它处理,可得到非枝晶结构合金,其凝固组织为球状的等轴晶,这种合金在固相含量６０％以下时流动性好,变形抗力很小。半固态金属成形是将具有上述特殊组织的、固液相共存的半固态坯料加工成所需形状、性能制品的技术,包括半固态锻造、半固态挤压、半固态轧制、半固态压铸等类型。它是７０年代出现的新兴技术,优点显著,前景良好,有望成为２１世纪金属制造关键技术之一。     

Effects of homogenisation conditions on semisolid microstructures of Al–Mg–Si–Mn alloys produced by D-SSF process

Abstract

The effects of different heating rates to a homogenisation temperature on the semisolid microstructure of Al–Mg–Si–Mn alloys are investigated. It is found that the size, morphology and distribution of the α-Al₁₂Mn₃Si₂ intermetallic compound (Mn containing dispersoid) depend on the heating rate in the homogenisation process. Fine spherical and homogeneously distributed Mn containing dispersoid particles are found in the slow heated samples (0˙7°C min^?1), while inhomogeneously distributed coarser particles with a rod-like shape are found in the rapid heated samples (110°C min^?1). The homogenised sample is deformed by 60% cold rolling. It is found that the recrystallised and semisolid grain sizes of the rapid heated sample are smaller than those of the slow heated sample in all conditions. Compared with the M4 alloy (0˙4 mass-%Mn), the M7 alloy (0˙72 mass-%Mn) has much finer semisolid grain size and smaller values of the shape factor close to 1. The Mn containing dispersoid greatly affects the semisolid grain size of the alloys. The results in this work show that the rapid heating in the homogenisation process is useful to produce high quality semisolid products of the Al–Mg–Si–Mn alloys.