Behavior and Mechanisms of Deformation in Intermetallic Compound Al_(66) Mn_9Ti_(25) +La

The influence of lanthanum on the microstructure, deformed behavior, microcrack susceptibility of intermetallic compound Al 66 Mn 9Ti 25 was investigated. Adding lanthanum into intermetallic compound Al 66 Mn 9Ti 25 , the lattice parameters are not changed and the Ll 2 structure is maintained. At the same time, the dendritical grain and fine second phase are obtained, which inhibits the microcrack initiation and intergranular failure. On the other hand, the movability of dislocation is enhanced and the compressive ductility is improved. The mechanism about the role of lanthanum in intermetallic compound Al 66 Mn 9Ti 25 was discussed.

Study of the Coarse Blocky Compounds in the As－cast 7075 Aluminium Alloys Containing Rare Earth Elements

The coarse blocky compounds in the as-cast 7075 aluminium alloys containing rare earth elements, neodymium, cerium or mischmetal were investigated by means of transmission electron microscope with EDX and scanning electron microscope. The blocky compounds in these alloys were identified as rare earth compounds, (Cr, Ti)2 RE (Al, X)20 (X is magnesium, copper and zinc),body-centred cubic, with 184 atoms to the unit cell , lattice parameter 1.453￣1. 458 nm, Vickers hardness 4000￣5600 MPa and calculated density 3400 kg/m3. The results show that the amount of blocky compounds in the alloys decreases with decreasing of Ti and Cr content or with increasing of cooling rate during solidification.

Effect of La on microstructure,mechanical properties and fracture behavior of Al/Mg bimetallic interface manufactured by compound casting

To improve the Al/Mg bimetallic interface,La was added into the Al/Mg bimetallic interface manufactured by a compound casting process.The effect of La addition on the microstructure,mechanical properties and fracture behavior of the Al/Mg bimetallic interface and the formation mechanism of the interface were studied in detail.Al_(11)La_(3),Al_(8)Mn_(4)La,Al_(20)Ti_(2)La,and other rare earth precipitates(RE precipitates)preferentially precipitated at the interface with La addition,while the number of the Al_(11)La_(3)and Al_(8)Mn_(4)La located in eutectic structure area(E area)gradually increased and aggregated in the interface with the increase of the La content.Besides,the matrix structure in different areas of the Al/Mg interface changed in different degrees,and the eutectic structure and primaryγ(Mg_(17)Al_(12))dendrites in the E area were refned,but the intermetallic compounds area(IMC area)had no obvious change.With the addition of the La,the interface was strengthened under the comprehensive effect of refnement strengthening and precipitation strengthening from the E area.When the La content increased to 1.0%,the shear strength of the Al/Mg bimetal reached the maximum of 51.54 MPa,which was 30.95%higher than the group without La addition.However,with the further increase of the La content,the large area aggregation of the Al_(11)La_(3)and Al_(8)Mn_(4)La occurred in the interface,leading to the separation of the matrix structure of the E area and the decrease of the shear strength of the Al/Mg interface.

Effect of Trace La Addition on the Microstructure and Mechanical Property of As-cast ADC12 Al-Alloy

The effects of addition of La on the microstructure of as-cast ADC12 A1-Alloy were investigated by using optical microscope （OM）, X-ray diffraction （XRD）, scanning electron microscope （SEM）, and energy disperse spectroscopy （EDS）. The experimental results showed that the a-A1 and eutectic Si crystals were modified with the addition of 0.3 wt% La. The eutectic Si crystals showed a granular distribution. At the same time, the alloy possessed the best mechanical property. When more than 0.3 wt% La was added to ADC12 aluminum alloy, the microstructure of as-cast alloy was coarsening gradually with the increase of the content of La and the mechanical property decreased. The effect of rare earth La which was added in ADC 12 A1-Alloy for up to 0.9 wt% had been investigated in this study. The dendrites ofADC12 Al-alloy was refined obviously and the morphology of Si crystals showed a particle structure when the addition of La reached 0,3 wt%. Besides, the acicular La-rich intermetallics in the alloy deteriorated the mechanical property of alloy： To avoid this unwanted phase, the amount of added rare earth La must be less than 0.6 wt%.

Dual characteristic of trace rare earth elements in a commercial casting Al-Cu-X alloy

The effect of rare earth elements on microstructure and mechanical properties of casting Al-Cu-X alloy （X = Mn, Ti, V, Cd, Zr） was investigated in as-cast and T6 conditions. Microstructure evolution was characterized by optical microscopy, scanning electron microscopy, and transmission electron microscopy. RE-containing intermetallic compounds （IMCs） formed in this alloy were indentified by X-ray diffraction （XRD） and energy dispersive spectroscopy （EDS）. It is shown that the additions of RE （60Ce-40La, wt%） result in the formation of Ce-rich blocky-shaped A12o（Ti, V）2RE and La-rich skeletal-shaped A18Cu4RE. Tensile results of samples after T6 treatment indicate that the strength and ductility increase slightly to 480 MPa and 9.7 %, respectively, with RE content increasing from 0 wt% to 0.3 wt%. This is due to the combinative hardening effects of reduced grain size, enhanced precipitation of 0＇ （Al2Cu） phase and Al20 Cu2Mn3 dispersed particles, and minor La-rich IMCs at the grain boundaries of α-Al dendrites. The decrease of strength of 0.5 wt% RE-added sample is ascribed to the aggregation of Al20（Ti, V）2RE IMCs inside the grains. The dual characteristic of rare earth elements was also discussed in terms of its positive and negative effects on mechanical properties.

Microstructure,wetting property of Sn-Ag-Cu-Bi-xCe solder and IMC growth at solder/Cu interface during thermal cycling

The effects of adding small amounts of cerium(Ce) to Sn-3.3 Ag-0.2 Cu-4.7 Bi solder on microstructure,wettability characteristic,interfacial morphology and the growth of interfacial intermetallic compound(IMC) during thermal cycling were investigated by optical microscopy(OM),scanning electron microscopy(SEM) and solderability tester.It is found that the p-Sn phase,Ag_(3)Sn phase and Cu6 Sn5 phase in the solder are refined and the wetting force increases.Ce is an active element;it more easily accumulates at the solder/flux interface in the molten state,which decreases the interfacial surface energy and reduces the driving force for IMC formation on Cu substrate;therefore,the thickness of IMC at the solder/Cu interface decreases when appropriate Ce was added into the solder.Moreover,the Ce-containing solders have lower growth rate of interfacial IMC than solders without Ce during the thermal cycling between-55 and 125℃.When the Ce content is 0.03 wt% in the Sn-3.3 Ag-0.2 Cu-4.7 Bi solder,the solder has the best wettability and the minimum growth rate of interfacial IMC layer.

添加微量稀土对SnBi基无铅钎料显微组织和性能的影响

研究了添加微量稀土对Sn58Bi基无铅钎料熔化温度、润湿性能、钎焊接头强度、高温时效前后IMC厚度的变化和显微组织的影响,并与添加一定量Ag对Sn58Bi钎料的试验结果做了比较。试验所用钎料为Sn58Bi,Sn58Bi0.5Ag,Sn58Bi0.1RE和Sn58Bi0.5Ag0.1RE,添加稀土为Ce基混合稀土。试验结果表明,添加微量稀土不仅抑制了Sn58Bi钎料高温时效引起的IMC的生长,而且细化了显微组织;微量稀土添加对钎料熔化温度没有明显影响,但能显著改善Sn58Bi钎料的润湿性能和接头强度,而且改善的程度优于添加微量Ag对Sn58Bi钎料的作用。

稀土导电铝合金的铸态组织和相组成

本文利用光学显微镜、扫描电镜、Ｘ射线衍射仪等，研究了Ｌａ、Ｃｅ对工业纯铝铸态组织和相组成的影响。结果表明，Ｌａ、Ｃｅ能细化工业纯铝的铸态组织，并和Ｆｅ、Ｓｉ等元素结合生成了二元或三元稀土化合物相。

稀土镨对金属间化合物Mg_2Si组织的影响

为了改善金属间化合物Mg2Si在常温下的组织形态与分布,采用在Al-30Mg2Si合金中添加不同量稀土元素镨(Pr)的办法,研究Pr对该合金中Mg2Si变质的影响.结果表明:适量的稀土元素Pr能够明显细化Mg2Si晶粒,改善其形态及其分布.当Pr加入0.2%时能够抑制Mg2Si树枝晶生长,且能使Mg2Si相均匀分布.当Pr加入0.6%～0.8%时,Mg2Si相呈规则多边体形态,且分布更加均匀,组织更加细小,可认为该含量时Mg2Si组织最完善,稀土Pr变质效果最好.当Pr增加到1.7%时,Mg2Si相再次呈不规则状,且分布不均匀.

Al_(66)Mn_9Ti_(25)+La金属间化合物的变形行为与机制

研究了微量稀土元素La对Al6 6 Mn9Ti2 5 金属间化合物显微组织、变形行为、裂纹生成的影响。在Al6 6 Mn9Ti2 5 金属间化合物中添加微量La ,保持L12 结构 ,晶格常数基本无变化 ,促进了晶粒枝晶化和第二相弥散化 ,起到一定的抑制微裂纹生成和扩展以及沿晶开裂的作用 ;同时 ,还可增强位错的可动性 ,使压缩塑性得到改善。探讨了La改善变形行为的机制。

微量Y对Mg-5Sn-1Si镁合金组织的影响

研究了稀土Y变质(0%~0.8%,质量分数)对Mg-5Sn-1Si合金显微组织的影响。通过XRD和SEM分析了该合金的组织和相组成。结果表明,受成分过冷的作用,适量Y能有效细化铸态组织。随着Y含量从0.2%增加到0.8%,生长抑制因子GRF值从Mg-5Sn-1Si-0.2Y的16.94增大到Mg-5Sn-1Si-0.8Y的17.96,枝晶臂间距平均尺寸从不含Y的Mg-5Sn-1Si合金的23.7μm减小至Mg-5Sn-1Si-0.8Y合金的12.5μm,减小了约47%。由于Y元素在Mg2Si表面的偏聚,Mg-Y二元相或是Mg-Si-Y三元相将在Mg2Si和α-Mg前沿析出,抑制了共晶Mg2Si的异向生长,使复杂汉字状的Mg2Si转变为棒状组织。当Y含量达到0.8%时,Y元素对Mg2Si变质效果最佳。通过XRD和SEM分析了该合金的相组成,合金由α-Mg基体、Mg2Sn、Mg2Si和少量的Mg24Y5和Mg Si Y组成。使用CASTEP软件包基于第一性原理,计算了三种Mg Si Y晶胞结构的结合能Ecoh,计算结果与Mg2Si结合能的对比,证实了Mg Si Y存在的可能性。

汽车微电子产品无铅焊料中添加稀土元素的研究

选用Sn57Bi1.0Ag无铅焊料,研究添加不同质量分数的混合稀土元素对无铅焊料/Cu界面及微观组织的影响,并分析了时效过程中界面处金属间化合物的生长规律。结果显示:随着稀土元素的加入,焊料中的富Bi相形貌及偏聚、富Sn相的比例和金属间化合物的分布都有所变化。当稀土添加量小于5%时,稀土元素对界面金属化合物的生长抑制作用随稀土元素添加量的增加而呈线性增强。

含稀土高硅铝合金的组织特征

为深入研究含稀土(RE)高硅铝合金的组织特征,将质量分数为0.08%P和质量分数为0.6%RE复合变质Al-20%Si-2%Cu-1%Ni-xMg(x=0.4%,0.8%)高硅铝合金浇入金属模具中成形.通过光学显微镜(OM)、X射线衍射(XRD)、扫描电镜(SEM)、能谱分析(EDS)等测试方法,分析了该合金的相组成.结果表明:合金中生成Mg2Si相、Al-Si-Cu-Ni-RE相、AlCuNi相、AlFeMnSi相等金属间化合物;合金中加入质量分数为0.6%RE能较好地变质共晶Si,但过剩的RE易生成针状的Al-Si-Cu-Ni-RE相,该富RE五元化合物的形态在T6热处理前后变化不明显;T6热处理后合金中粗大的AlCuNi相粒状化,且分布较均匀.

稀土元素Sm对AZ61镁合金的组织与力学性能的影响（英文）

采用OM,XRD,SEM和EDS等分析手段,研究了不同含量的稀土元素钐（质量分数,0.0%,0.5%,1.0%,1.5%和2.0%）对AZ61镁合金组织与性能的影响。结果表明：在含钐为0.5%～2.0%的AZ61镁合金中发现了大量的颗粒状Al2Sm金属间化合物（体积分数为0.4%～2.2%）,这些颗粒的直径为1～7μm。当合金中稀土元素钐的含量从0.0%增加到2.0%时,合金中Al2Sm颗粒尺寸逐渐增大,而β-Mg17Al12的含量却不断减小。经693 K固溶24 h的含钐AZ61镁合金的晶粒尺寸随着钐含量的增加而先减小后增加,当钐含量为1.0%时,合金的晶粒尺寸最小。固溶态AZ61镁合金中的钐含量达到1.0%时,合金的极限抗拉强度、屈服强度和延伸率都达到最大,分别为215、142 MPa和4.1%。

Y对Cu的显微组织和性能的影响

借助金相显微镜、扫描电子显微镜、能谱仪、透射电镜、X射线衍射仪及涡流电导率仪、硬度仪研究了真空感应制备的Cu-Y合金的组织和性能。实验结果表明,Cu-Y合金的组织随着Y含量的增大而不断细化,未固溶的Y元素在Cu中以中间相化合物六方Cu7Y的形式富集在晶界处,退火后Cu7Y相会分解为立方Cu5Y相。Cu-Y合金的导电率随Y含量的增加会先上升再降低,当Y含量为0.05%时导电率达到最大102%IACS。而显微硬度随着Y含量的增加而不断升高,主要硬化机制为细晶硬化和第二相硬化。