Ce的添加对SnAgCu系钎料组织和性能的影响

通过向Sn-0.3Ag-0.7Cu系无铅焊料中添加微量稀土Ce,研究不同稀土含量对Sn-0.3Ag-0.7Cu合金的熔化温度和润湿性的影响,同时利用扫描电子显微镜(SEM)对焊料的显微组织进行了分析.实验结果表明,添加Ce对焊料的熔化温度影响不大,但对合金的润湿性和微观组织影响较大.当ω(Ce)=0.10%时,焊料合金的综合性能较好.     

Ce对Mg-Al-Zn系合金焊接接头显微组织及力学性能的影响

研究了Ce对Mg-Al-Zn系合金焊接接头显微组织及力学性能的影响,结果表明,稀土Ce对改善AZ31、AZ61合金接头强度及提高接头有效系数有明显作用,添加1.0％Ce将使AZ31合金的焊接接头有效系数由0.66提高到0.81.Ce能改善Mg-Al-Zn合金焊接性的原因是Ce与Al形成高熔点的Al4 Ce相,减少了粗大的Mg17 Al12相的数量并细化了焊缝区的晶粒.通过分析AZ31、AZ61Ce镁合金焊接熔池的特点和结晶过程,获得了焊缝边缘区域依托母材未熔晶粒形核与长大的联生生长机制.     

Ce含量对X100管线钢显微组织和耐腐蚀性能的影响

为了研究稀土元素Ce对X100管线钢显微组织和耐腐蚀性能的影响,利用蔡司显微镜、场发射电子显微镜及其配套的能谱仪和电化学工作站对不同Ce含量的4种试验钢0,1,2,3号(Ce质量分数分别为0,0.001 7%,0.002 8%,0.004 9%)进行测试。结果表明：随着Ce含量的增多,试验钢表面的晶粒尺寸减小,Al₂O₃夹杂被改性为CeAlO₃夹杂和Ce₂O₃夹杂。浸泡7 d后,4种试验钢的腐蚀电位均比较接近;浸泡30 d后3号试验钢的腐蚀电位较之前提高了8.94%,2号和1号试验钢的腐蚀电位分别较之前提高了6.34%和6.06%;浸泡45 d后,1号试验钢的腐蚀电位较7 d时降低了10.38%,其他3种试验钢的腐蚀电位变化不大。0号试验钢的容抗弧半径随浸泡时间的延长而逐渐减小,3号试验钢的容抗弧半径增大得最为明显。测试结果均表明,Ce含量的增加会提高试验钢的耐腐蚀性能。     

稀土对AA7075合金显微组织和性能的影响

本文讨论了AA7075合金中加入稀土元素后显微组织及性能的变化情况,指出:稀土元素加入AA7075合金后,在结晶过程中形成了一种粗大的新相,并因此降低了材料的力学性能和耐蚀性能。     

等温时效对SnAgCu/Cu焊接接头显微组织及强度的影响

研究了SnAgCu焊料与铜基的接头在150℃等温时效后,接头界面金属间化合物的形成与转变.用扫描电镜观察在时效过程中焊接接头的显微组织演变.用X射线能谱仪测定了化合物的成分.结果表明,回流焊接时,在焊料和铜基板之间形成了Cu6Sn5化合物层,随着时效时间的增加,Cu6Sn5的晶粒大小逐渐增加,并且形态逐渐从扇贝状依次转变为针状和杆状,最后转变为颗粒状.与此同时,在焊料及Cu6Sn5金属间化合物层之间形成了杆状的Ag3Sn.焊接接头的抗拉强度的测量表明,抗拉强度随着时效时间的增加开始略有增加而后逐渐下降.断口观察发现,随着时效时间的增加,断裂源从焊料内部向Cu6Sn5界面移动.在化合物层界面发生的断裂是由于化合物晶粒粗化和Cu6Sn5化合物层厚度的增加造成的.     

稀土元素对AgCuNi合金铸态显微组织的影响

研究了稀土Y和复合稀土La、Y对AgCu-Ni合金铸态显微组织及力学性能的影响。研究结果表明,随着Y含量的增加,铸态组织晶粒尺寸减小,并由树枝晶逐渐转变为胞晶;稀土元素以化合物(AgCu)5RE形式偏聚在晶界上,当La、Y复合添加时,稀土元素呈共生态在晶界析出;随着RE含量的增加,AgCuNiRE合金显微硬度增加,当RE含量由0.6%增加到2.2%时,合金硬度值比AgCuNi合金增加了0.26~1.28倍。     

冷却速度对无铅焊料Sn-3．5Ag合金微观组织和显微硬度的影响

在～10^2K／s、～10^3K／s和～10^4K／s的冷速条件下研究了凝固速度对无铅焊料Sn-3．SAg合金微观组织和显微硬度的影响。结果表明：由于非平衡凝固条件下动力学过冷的影响，导致了该共晶合金实际凝固过程开始于平衡共晶凝固点以下，合金凝固组织中包含初生β-Sn枝晶，且该初生β-Sn枝晶组织随合金凝固速度的提高而发生细化。另外，维氏硬度测试结果表明，无铅焊料Sn-3．5ag合金在不同冷速条件下的凝固组织与显微硬度的关系符合经典Hall-Petch关系式，即初生β-Sn枝晶细化能显著提高焊料合金的显微硬度。     

稀土Er和Ce复合改性对过共晶Mg-Si合金组织与性能的影响

通过金相、SEM、EDS和XRD等方法研究了稀土元素Er、Ce复合改性对过共晶Mg-3.2Si合金中初生Mg_2Si相的影响,并探讨了改性机制。结果表明,在过共晶Mg-3.2Si合金中,添加约0.6%(质量比,下同)Er时,初生Mg_2Si相的平均尺寸由150μm减小到40μm,其形态从粗大树枝状变为不规则多面体;在此基础上,继续添加1.0%Ce,可获得5~10μm大小的多面体或球状初生Mg_2Si相,改性效果最佳;但稀土添加过量,会出现过改性现象。改性机制:稀土Er和Ce吸附或富集在初生Mg_2Si相表面,降低固液界面张力,减小临界形核功,有利于更多初生Mg_2Si晶核的生成;稀土Er和Ce在初生Mg_2Si相的表面富集,减小了晶向之间的相对生长速度,使初生Mg_2Si相从粗大树枝状变为不规则多面体形状;合金凝固时,稀土Er与Ce的晶体结构相同,形成了连续固溶体。当稀土添加量为0.6%Er和1.0%Ce时,Mg-3.2Si合金试样的抗拉强度σb与伸长率δ分别提高到127 MPa和3.7%最大值。     

稀土Ce对涂层阳极电催化性能的影响

在涂层阳极中掺入稀土Ce对电催化性能的影响报道较少.利用热分解方法在不同温度下制备了不同摩尔分数Ce的三元涂层Ru0.3Ti(0.7～x)CexO2,通过极化曲线测试、交流阻抗谱测试、扫描电镜观察,研究了所制备涂层的电催化活性.结果表明:Ce的掺入量有一个最佳范围,摩尔分数为0.2～0.3时涂层阳极电催化性能最好;适当的热分解温度有利于含Ce涂层阳极性能的提高,最佳温度为450℃;在阳极涂层中引入Ce可以提高其电催化活性.     

冷却速度对无铅焊料Sn-3.5Ag合金微观组织和显微硬度的影响

在～102K/s、～103K/s和～104K/s的冷速条件下研究了凝固速度对无铅焊料Sn-3.5Ag合金微观组织和显微硬度的影响.结果表明:由于非平衡凝固条件下动力学过冷的影响,导致了该共晶合金实际凝固过程开始于平衡共晶凝固点以下,合金凝固组织中包含初生β-Sn枝晶,且该初生β-Sn枝晶组织随合金凝固速度的提高而发生细化.另外,维氏硬度测试结果表明,无铅焊料Sn-3.5Ag合金在不同冷速条件下的凝固组织与显微硬度的关系符合经典Hall-Petch关系式,即初生β-Sn枝晶细化能显著提高焊料合金的显微硬度.     

Effects of trace rare earth Nd addition on microstructure and properties of SnAgCu solder

Effects of rare earth Nd on solderability of the Sn3.8Ag0.7Cu alloy were studied by wetting balance method, and the mechanical properties (such as pull-force and shear-force) of the joints soldered with SnAgCu–XNd solders were determined using STR-1000 joint strength tester. Moreover, the microstructures of SnAgCu–XNd solders bearing different amount of Nd as well as the intermetallic compounds (IMCs) formed at solder/Cu interface during soldering have been investigated using optical microscopy, scanning electron microscopy and energy dispersive X-ray analysis, respectively. The results indicate that trace amount of Nd addition can remarkably improve the solderability and mechanical properties of SnAgCu solder. At the same time, it is found that rare earth Nd in SnAgCu solder could refine and improve microstructure of the solder, some bigger IMC plates in SnAgCu solder were replaced by fine granular IMCs. Moreover, the thickness of the intermetallic layer at the Cu/solder interface was reduced significantly. In summary, we suggest that the most suitable content of rare earth Nd is about 0.05 wt% and it will be inadvisable when the Nd exceeds 0.25 wt%.     

Effect of rare earth addition on shear strength of SnAgCu lead-free solder joints

In the present study, the effect of adding trace amount of rare earth (RE) on the shear strength of Sn3.8Ag0.7Cu lead-free solder joints has been investigated. The shear strength of the solder joints as-reflowed and after aging at 150 °C for 168 and 336 h was measured at a constant loading rate of 0.3 mm/min and room temperature. The investigation indicates that the shear strength of Sn3.8Ag0.7Cu0.1RE solder joints is lower than that of Sn3.8Ag0.7Cu solder joints. The shear strength of both Sn3.8Ag0.7Cu solder joints and Sn3.8Ag0.7CuRE solder joints was reduced after aging at elevated temperature. However, the shear strength reduction rate of the Sn3.8Ag0.7Cu solder joints was much faster than that of Sn3.8Ag0.7CuRE solder joints. Moreover, the fracture surfaces were examined by scanning electron microscopy (SEM) and the thickness of intermetallic compounds layer (IML) in the solder joints that join Cu substrate was measured. The results indicated that the addition of rare earth elements suppresses the growth of the thickness of intermetallic compounds layer.     

Effects of rare earths on properties and microstructures of lead-free solder alloys

In order to further enhance the properties of lead-free solder alloys such as SnAgCu, SnAg, SnCu and SnZn, trace amount of rare earths were selected by lots of researchers as alloys addition into these alloys. The enhancement include better wettability, physical properties, creep strength and tensile strength. For Sn3.8Ag0.7Cu bearing rare earths, when the rare earths were La and Ce, the creep-rupture life of solder joints can be remarkably improved, nine times more than that of the original Sn3.8Ag0.7Cu solder joints at room temperature. In addition, creep-rupture lifetime of RE-doped solders increases by over four times for SnAg and seven times for SnCu. This paper summarizes the effects of rare earths on the wettability, mechanical properties, physical behavior and microstructure of a series of lead-free solders.     

SnAgCu无铅焊膏可印刷性及焊点微观结构研究

焊膏的印刷质量及焊点的微观结构直接影响产品的最终性能和使用效果.通过对焊膏印刷性能及焊点微观结构的研究,可以制定出合适的印刷和焊接工艺,从而提高产品的最终性能和使用效果.本文以紧耦合气雾化法制备的SnAgCu合金粉末为原料,对不同质量配比下焊膏的流变和塌陷性能以及焊点的微观结构进行研究,采用旋转流变仪和扫描电镜分别对焊...     

稀土元素对Cu-Ag原位纤维复合材料的结构与性能影响

研究了稀土添加剂Ce、Y和Gd对Cu-Ag原位纤维复合材料结构和性能的影响,制备了具有高强度和高导电性相结合的Cu-Ag-Ce原位纤维复合材料.结果表明添加少量稀土元素Ce、Y或Gd,使Cu-Ag原位纤维复合材料铸态树枝晶状结构演化为胞状树枝晶、明显的胞状和不规则胞状晶结构,富Ag相有球化倾向.稀土Ce可提高材料的综合性能,Y和Gd对材料的综合性能没有提高作用.     

Mechanical and microstructural properties of SnAgCu solder joints

Mechanical and microstructural properties of SnAgCu solder joints with hypoeutectic, eutectic and hypereutectic compositions were studied. Eutectic SnPb joints were used as the reference. Reflowed lap shear specimens made of FR-4 glass epoxy printed circuit boards with OSP and NiAu surface finishes were used in the tests. Mechanical properties and microstructural features of the joints were examined in the as-reflowed condition and after isothermal aging at 85 °C for 1000 h. Both the composition and PCB surface finish had a notable effect on the mechanical behaviour of the SnAgCu solder joints. The shear strength value of SnAgCu solder joints was mainly dependent on the size and distribution of Ag₃Sn dispersions. The coarseness of the dispersions depends strongly on the amount of Ag in the solder alloy, the cooling rate after the reflow and the aging history of the solder joints.     

Effect of rare earth Y addition on the microstructure and mechanical properties of high entropy AlCoCrCuNiTi alloys

A series of AlCoCrCuNiTiY_x (x values in molar ratio, x = 0, 0.5, 0.8, 1.0) alloys have been prepared using vacuum arc melting. Classical high entropy diffraction peaks corresponding to a BCC crystal structure and some Cu, Cr peaks are observed for the AlCoCrCuNiTi alloy. However, with the incorporation of rare earth element Y, the BCC diffraction peaks disappeared and were replaced by new compounds like Cu₂Y and AlNi₂Ti. A typical cast dendrite structure with Cu-rich dendritic regions and Cr-rich rosette-like shape precipitations are found in the AlCoCrCuNiTi alloy. In the AlCoCrCuNiTiY_x alloys, Y segregated preferentially to Cu and combined as bulky Cu₂Y compound. The maximum stress of the AlCoCrCuNiTi alloy is 1495 MPa, but reduces intensively after the incorporation of Y due to the formation of bulky Cu₂Y. For all the alloys, the compressive fracture mechanism is observed to be cleavage fracture.     

Effects of rare earth additions on structures and properties of rapidly solidified copper alloys

Abstract

Copper based Cu–RE alloys (where RE represents lanthanum, neodymium, or samarium) with alloying content up to 16 wt-% were prepared by chill block melt spinning into ribbons of thickness between 40 and 100 μm. The melt spun ribbons were heat treated isochronally for 2 h at 300, 400, 500, 600, 700, and 800°C, respectively. The melt spun and heat treated ribbons were tested for microhardness and resistivity and were characterised by optical and transmission electron microscopy (TEM) and X-ray diffractometry (XRD). Microstructures were of the typical zone B type for Cu–1RE and Cu–3RE ribbons and of the zone B/zone A type for Cu–5RE, Cu–8RE, and Cu–12RE ribbons. Only microstructures of the zone A type were found in Cu–15La ribbons. The metastable extended solid solubilities of the rare earth elements were evaluated by measurements of the lattice parameters of the supersaturated solid solutions and significant extension from the equilibrium solid solubility was found for all three alloys. The secondary phase was identified by TEM and XRD as Cu₆RE for all ribbons except Cu–15La ribbons in which metastable Cu₅La and Cu₁₃La phases were also found. Observations using TEM and XRD also showed a reduction in the α-Cu grain size of the as spun ribbons with increasing alloying content, producing nanosized α-Cu grains on the chill side of the ribbons. Heat treatment of the ribbons at 400°C for 2 h produced no significant coarsening of α-Cu grains as the size of these grains was still in the nanometer region. Both α-Cu and Cu₆RE grains coarsened as a result of heat treatment for 2 h at temperatures of 600°C and above for all the alloys.