Development on research of advanced rare-earth aluminum alloy

The active mechanisms of rare earth element erbium ( Er ) in part of aluminum alloys were investigated. Based on the investigation of the effect of the unitary rare earth elements (Er, La, Y, Ce, Nd, Gd, and Sc) and the transition element zirconium on the aluminum alloys, it is concluded that, with Er alloyed, high purity aluminum and Al Mg alloys are featured with refined grain structure, superior heat stability and even higher hardness or tensile strength with unchanged ductility; but Er is not beneficial to the mechanical property of Al Cu alloy, so is Sc. It may also be concluded, to most of the aluminum alloys, Er can be an effective alloying element, like Sc; and for the lower price of Er, the cost of modifying aluminum alloys by Er will be reduced.

Effect of Rare Earths on Hot Cracking Resistant Property of Mg-Al Alloys

The effect of rare earths （RE） ranging from 0.1% to 1.2%（mass fraction） on hot cracking resistant property of Mg-Al alloys was investigated. The results show that hot cracking resistant property of Mg-Al alloys remarkably declines with an increase of RE addition. The causes of the decline are as follows： First, grain coarsening of Mg-Al alloys caused by RE addition reduces the fracture strain required for hot crack initiation. Second, RE reduces the eutectic microstructure of Mg- Al alloys, and as a result, shortens the time that the feeding channel remains open, making it difficult to feed the alloy. Furthermore, RE elevates the eutectic reaction temperature, which leads to the decrease in the strength of the interdendritic liquid film at the late stage of solidification. Third, when a-Mg dendrites form continuous skeletons, the interdendritic Al11 RE3 phase tends to block the feeding channels and increases the difficulty of feeding. Last, the shrinkage ratio discrepancy between Al11RE3 phases and α-Mg matrix is prone to cause shrinkage stress and promote hot crack initiation.

Effect of Rare Earth Cerium on Yield Strength Anisotropy of Al-Li Alloy Sheet and Its Theoretical Prediction

The variation of yield strength along rolling direction, transverse direction and 45° to transverse direction of 2090 Al-Li alloy and 2090+Ce alloy sheet containing rare earth cerium was comparatively investigated. The difference of deformation texture in these two alloy sheets was analyzed by means of X-ray orientation distribution function (ODF). The results show that cerium has the effects of enhancing the Brass and S rolling texture components and reducing the recrystallized texture components of Cube and Goss. This is the reason that the anisotropic degree of yield strength in 2090+Ce sheet is higher than that of 2090 alloy sheet. The prediction of yield strength along various orientations in two alloy sheets was done based on Taylor/Bishop-Hill model, and the strengthening effect of grain boundary was evaluated using Hall-Petch relationship. A modified plastic inclusion model was proposed using the concept of grain-orientation factor and T1 phase orientation factor by fitting with tensile test results.

Study of rare earth element effect on microstructures and mechanical properties of an Al-Cu-Mg-Si cast alloy

The improvements of microstructures and properties of a high strength aluminum cast alloy were studied. The effects of rare earth elements on the microstructures and mechanical properties of the high strength cast alloy Al-Cu-Mg-Si were investigated. The result shows that the addition of rare earth elements can change the microstructures in refining the grain size of the alloy and making the needle-like and laminar eutectic Si to a granular Si. With the increase of the rare earth, the tensile strength and elongation of the alloy increase first and then fall down. The mechanical properties of the alloy will reach the highest value when the content of rare earth elements is about 0.7%.

Influence of rare earth elements on corrosion resistance of BFe10-1-1 alloys in flowing marine water

The corrosion behavior of BFe10-1-1 alloy with different rare earth （RE） contents in simulated flowing marine water was investigated by X-ray diffractometer and scanning electron microscope （SEM）. It was demonstrated that the corrosion rate of BFel0-1-1 alloy with the same chemical compositions in faster flow velocity of marine water was higher than that in a lower flow velocity of marine water. Fixing the flow velocity, BFe 10-1-1 alloy had the best flushing corrosion resistance when the RE content was 0.04wt.%. The consequence of such good corrosion resistance was attributed to the formation of compact protective film on alloy surface containing RE phase such as CeNis. The RE-contained film combines with other corrosion products firmly, which was difficult to fall off from the alloy surface in the flowing marine water. Additionally, SEM analysis confirmed that pitting mechanism, which would be transformed to spalling mechanism gradually with further increasing RE content, was the prevalent mechanism when the alloy contained 0.04wt.%RE.

THE EFFECT OF RARE EARTH ELEMENTS ON THE SOLIDIFICATION BEHAVIOR OF Al-Mg ALLOYS

The effect of rare earth element on the solidification behavior of Al-Mg alloy was investigated in a directional solidification apparatus.It was found that during the solidification process.the rare earth element segregated in the liquid at sold-liquid interface,changed the solidification morphology and reduced the secondary arm spacing markedly.

HEAT TREATMENT STRENGTHENING EFFECTS OF RARE EARTHS ON Mg-9Al ALLOY

Mg-9Al-xRE magnesium alloys were studied, where, x is 0, 0.4. 0.8. 1.2 and 1.6% (in weight percent, wt%), respectively. Influence of rare earths (RE) on micro structure. and strength in both T4 (solute heat treatment) and T6 (solute heat treatment and artificial ageing treatment) were investigated. Strength of specimen was tested at ambient temperature. The micro structure was analyzed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis. RE additions improved T4 tensile strength of the treated alloys. Small addition (0.4wt%) of RE greatly improved the strength of ageing treated (T6) Mg-9Al alloy, but further additions caused decreasing.

Effect of Rare Earth on Superplasticity of Zn-5Al Eutectic Alloy

The superplastic deformation curves of Zn 5Al eutectic alloy containing small amount of rare earth were measured, and the influence of rare earth on structure and superplasticity characteristics of the alloy was examined with optical microscope, XDF and TEM. The results show that the elongation of Zn 5Al eutectic alloy can be increased if less than 0.2 %(mass fraction) misch metal was added. Rare earth which exists in the form of compounds Al 2CeZn 2 and CeZn 3 can refrain the dissolution and diffusion of Zn to Al and postpone the saturation of the diffusion dissolution zone(DDZ) above 350 ℃, and in such a way boost up α/β interface sliding which benefits the superplasticity.

Refining Effect of a New Al3Ti1B1RE Master Alloy on Al Sheets Used for Can Manufacture and Behavior of Rare Earths in Master Alloy

The refining effect of Al3Ti1B1RE master alloy on Al sheets used for pressure can manufacture and the behavior of mixed rare earths in master alloy were investigated with XRD, OM, SEM and EDAX. It is found that the refining effect of the refiner on the material has superiority over foreign or domestic Al5Ti1B refiner, and the refiner still retains its refining ability for 6 h after adding it to molten Al, thus improving the strength and plasticity of the material remarkably. The excellent refining effect and stability of AlTiBRE refiner result from that RE can lower the surface energy of molten Al and improve the wetting characteristics of molten Al on refinement nuclei such as TiAl 3, TiB 2, etc., thus giving full play to the effect of heterogeneous nucleation and impeding the congregating tendency of TiB 2 phase in molten Al. At the same time, RE gathering in front of solid/liquid interface are also easy to cause composition supercooling in molten Al, thus impeding the growth of α Al grains and promoting α Al nucleation on refinement nuclei. In addition, RE also play certain role in purification and grain refinement, or modification, especially their effect of purification can improve the metallurgical quality of AlTiBRE master alloy.

Rare Earth Metals in Light Alloys

A review of crystallochemical thermodynamic and phase diagram data of Mg RE and Al RE based systems is presented. On the basis also of their possible applications, special attention is given to the Mg rich and Al rich alloys and to the effects of rare earth additions on their properties. A summary of the experimental work carried out by our research group on several binary and ternary alloys is reported: that is Mg RE, Al RE, and Mg RE RE′ and Al RE RE′ with two different rare earth metals. A number of regularities observed in the formation and in the crystallochemistry of binary and ternary Mg rich or Al rich phases are summarised and discussed. Their application to a fine planning of alloys having a well defined structure is suggested.

Effect of mixed rare earth oxides and CaCO_3 modification on the microstructure of an in-situ Mg_2Si/Al-Si composite

The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive spectrum analysis. The results showed that the morphol-ogy of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape,their sizes decreased from 75 μm to about 25 μm,and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth o...

Microstructure evolution of rare earth Pr modified alumina-silicate short fiber-reinforced Al-Si metal matrix composites

Al-Si metal matrix composites (MMCs) reinforced with 20 vol.% alumina-silicate shot fibers (Al2O3-SiO2(sf)) were fabricated by an infiltration squeeze method. Pure Pr metal was added into these composites. The effect of Pr addition on the microstructure evolution of Al-Si MMCs was investigated by SEM,TEM,and EDS. Pr addition is favorable to make uniform microstructures with the modified eutectic Si crystal. PrAlSi phase with high contents of Pr and Si is observed on the interface between the fiber and the m...

Effect of rare earth Pr on microstructure and mechanical properties of Al_2O_3-SiO_2(sf)/Al-Si composites

The Al2O3-SiO2(sf)(volume fraction,20%)/Al-12.6Si metal matrix composites(MMCs)with or without rare earth Pr addition were fabricated by infiltration squeeze method.Effect of Pr addition on microstructures and fractographs of Al-Si MMCs was investigated by SEM and TEM.Tensile properties at room temperature and 200℃were tested.It is shown that the addition of Pr is favorable to produce uniform microstructures and modify the eutectic Si crystal effectively.Compounds/intermetallics with high content of Pr are formed at the interface between short fiber and matrix.Yield strength(σ 0.2 ),ultimate tensile strength(σ b)and fracture elongation of Al-Si MMCs are improved by adding suitable amount of Pr.Compared with those values of Al-Si based MMC at 200 ℃,σ 0.2 andσ bof MMC with 0.29%Pr are increased by 33%and 55%,respectively.The tensile fracture surface of Al-Si MMCs with Pr addition presents ductile fracture features.

Mixed rare earth metal conversion coatings on 2024 alloy and Al6061/SiC_p metal matrix composites

The processes of mixed rare earth metal (REM) conversion coatings on 2024 alloy and Al6061/SiC p metal matrix composites (MMC) were introduced. The coatings were examined to be honeycomb like feature by scanning electron microscope. X ray diffraction analysis revealed that the coatings are amorphous structure. The results of X ray photoelectron spectroscopy indicated that the mixed REM conversion coatings consist predominantly of Ce and O, the contents of other rare earth elements (such as La, Pr) are relatively low, the coatings are about 2～4 μm thickness with excellent adhesion and wearability. The results of mass loss test showed that the mixed REM conversion coatings produce corrosion resistant surface of 2024 alloy and Al6061/SiC p. [

Effect of Rare Earth Metals on Microstructure of Directional Solidified Al－3Li Alloy

The effect of rare earth metals (La, Ce, Pr, Nd, Mm and Ymm) on microstructure of directional solidified Al-3Li alloy has been studied. Results show that rare earth metals reduce the distance between primary longitudinal dendrites for Al-3Li alloy, which is related with species, content of rare earth metals and solidification rate of the alloy. RE is mainly segregated at grain boundaries. Constitutional supercooling formed in RE-rich regions during solidification is considered to be the main factor of modification of microstructure.

Experimental Study of the Phase Equilibria in the R-Al-Si Ternary Systems (R: Rare Earth Element) the Ho-Al-Si Isothermal Section at 500?C

The effect of holmium addition to the Al-Si system has been experimentally studied, as the isothermal section at 500?C. The constitution of the alloys has been determined by means of scanning electron microscopy (SEM), electron microprobe analysis (EDXS) and X-ray powder diffraction. The knowledge of the phase relationships in the R-Al-Si ternary systems (R: rare earths element) is essential to deeply understand the technological properties of the Al-Si based alloys, that are useful in different industrial fields. In the system investigated have been identify nineteen ternary fields and twelve two phase fields. Three ternary compounds have been found in this ternary section: τ2-Ho2Al3Si2 (mS14-Y2Al3Si2), τ4-Ho2AlSi2 (oI10-W2CoB2) and τ5-Ho6Al3Si (tI80-Tb6Al3Si). The results obtained can be useful compared with the other known R-Al-Si systems also for predictive purposes.

国产Zn-5%Al-混合稀土合金镀层高钒封闭索丝耐久性研究

以国家速滑馆首次应用的国产Zn-5%Al-混合稀土合金镀层高钒封闭索丝为研究对象,对其使用性能、基本特性及耐久性等进行研究。采用了国家速滑馆内部高空索体实际服役环境处的大气暴露试验方式,综合考虑索在加工安装过程中易产生的损伤,对索丝试件进行了划痕、刮擦、焊点的预制缺陷设计,研究了含预制缺陷的国产Zn-5%Al-稀土合金镀层高钒封闭索丝在真实使用环境中的大气腐蚀行为规律,并采用力学性能测试研究了索丝在服役环境大气腐蚀作用下的力学性能变化规律及不同缺陷对力学性能的影响。结果表明,加工安装过程中在索丝表面合金镀层产生的划痕、刮擦、焊点等损伤,会破坏合金镀层的完整性。大气暴露试验和力学性能试验中,三类缺陷对索丝金属镀层防大气腐蚀性能和单丝抗拉强度均有负面影响,其中焊点缺陷影响最大,单丝抗拉强度下降约40%。

锌镁比对Al-Zn-Mg-Cu-Er-Sc-Zr合金显微组织与耐腐蚀性能影响的研究

通过调整Al-Zn-Mg-Cu-Er-Sc-Zr合金中的Mg元素含量,研究了Zn/Mg比的变化对合金相演变以及腐蚀性能的影响规律。结果表明:Al_(8)Cu_(4)Er相、Al_(3)(Er,Sc)相与含Fe相存在明显的伴生关系,二者依附于含Fe相生长。Zn/Mg比的变化可显著改变三者间的交互形式,高的Zn/Mg比例有利于稀土相独立生长,且在比值为4.18的条件下,Al_(8)Cu_(4)Er相与含Fe相均得到了显著细化。细化的晶界第二相使腐蚀坑深度仅为82μm,而连续的伴生混合相、粗大稀土相等均会不同程度降低合金的耐蚀性能。

富Ce稀土对多元Al-Si活塞合金凝固组织的影响

采用DSC以及光学显微镜与扫描电镜研究了富Ce稀土(0.1wt%,0.3wt%,0.5wt%)对多元近共晶Al-11.5Si-4Cu-2Ni-1Mg-0.5Fe(wt%)活塞合金凝固组织的影响。发现富Ce稀土加入对该合金的共晶硅和多种第二相的凝固温度、形态与体积分数均有明显影响。富Ce稀土的加入,使Al-Si共晶温度降低,T-Al_(9)FeNi相和δ-Al_(3)CuNi相析出温度升高。富Ce稀土加入量0.3wt%时,共晶硅变质效果最佳,T-Al_(9)FeNi相由初始的板条状转变为小块状,体积分数减小到3.22vol%,δ-Al_(3)CuNi相由初始的片状转化为鱼骨状,体积分数增加到6.47vol%。富Ce稀土中La、Ce原子在凝固过程中富集在固液界面前沿,增大了成分过冷,细化共晶组织。当富Ce稀土含量为0.5wt%时,合金中出现长针状富稀土相。

稀土元素对Zn-5Al-2Mg-0.5Si合金微观组织和性能的影响

为了开发新型高耐腐蚀热浸镀锌合金材料,使用微合金化方法将稀土元素添加到Zn-5Al-2Mg-0.5Si合金中,并对试样的微观组织、腐蚀性能、硬度和腐蚀产物进行了分析和表征。结果表明:稀土元素的加入可以为合金提供异质形核核心,增加形核数目,细化晶粒,提高合金的硬度。另外稀土元素还可以增加电荷转移的阻力,降低腐蚀反应的驱动力,促进腐蚀产物中Zn_(5)(OH)_(6)(CO_(3))_(2)的生成,该物质可能与合金腐蚀性能的提高紧密相关。