Properties of (Fe-B)-doped Sn-1.0Ag-0.5Cu solders prepared by mechanical alloying

To introduce boron(B)into the Sn-1.0Ag-0.5Cu(SAC 105)solder,based on the thermodynamic calculations,iron(Fe)is a competent carrier component for bonding B and Sn.The Sn-Fe-B master alloys were prepared by mechanical alloying initially;then,the SAC105-0.05(Fe-B)and SAC105-0.1(Fe-B)solder alloys were prepared using 72-h-milling Sn-Fe-B master alloys.The preparation process and the properties of solders were studied in this work.For the Sn-Fe-B master alloys,the results show that with the increase in the ball-milling time,the powder changes illustrate a cold welding-crushingcold welding cyclic process.Moreover,the supersaturated solid solubility of(Fe-B)increases gradually in the alloys' matrix and the lattice distortion increases to 0.167% after 72-h milling.Meanwhile,the alloying degree is increasingly apparent,and after 72-h milling,the content of B in the Sn matrix reaches 2.38 wt%.For the solder alloys,with the(Fe-B)content increasing,the melting point decreases and a significant grain refinement occurs in the matrix.Compared to the benchmark SAC105,the hardness of SAC105-0.05(Fe-B)and SAC 105-0.1(Fe-B)solder alloys prepared by this method is improved by 20.65% and 34.79%,respectively.The present research provides a novel approach for introducing the immiscible component into the lead-free solder alloys.     

Al-(7.8~9.0)Zn-1.6Mg-(1.0~2.2)Cu合金铸态及其均匀化组织

采用光学显微镜(OM)、X射线衍射(XRD)、差示扫描量热仪(DSC)和扫描电镜(SEM)及其附件能谱仪(EDX)研究Al-(7.8~9.0)Zn-1.6Mg-(1.0~2.2)Cu铝合金的铸态及其均匀化组织。结果表明:该铝合金的铸态凝固组织由α(Al)基体+Mg(Zn,Al,Cu)2非平衡共晶相组成;铸态组织中粗大非平衡共晶组织的体积分数随着Zn含量的增加而增大,且伴随其周围析出的条状、细小Mg(Zn,Al,Cu)2粒子也逐渐增多、粗化;当Cu含量(质量分数)为1.0%、1.4%、2.2%时,铸态组织晶内的独立第二相分别为T(Al2Zn3Mg3)相、S(Al2CuMg)相、T(Al2Zn3Mg3)相+θ(Al2Cu)相;各成分合金经过(470℃,24h)均匀化处理时,基体中仅剩下均匀化过程无法消除的尺寸较小、数量较少的初生富Fe相。     

Low-Temperature Oxidation of Cu(100), Cu(110) and Cu(111)

To better understand the oxidation kinetics of Cu, the oxidation kinetics of Cu(111) in the low-temperature range of 313–453 K were studied using spectroscopic ellipsometry. The low-temperature oxidations of Cu(100) and Cu(110) were also investigated and compared against Cu(111). Similar to the kinetics of Cu(111), those of Cu(100) and Cu(110) depend on the oxide thickness, which exhibit logarithmic behavior for oxide thicknesses under 5 nm, cubic behavior in the range of 5–25 nm, and parabolic behavior over 25 nm. A diffusion model was developed to simulate the kinetics of Cu(100), Cu(110) and Cu(111).     

Experimental investigation of the Cu–Si phase diagram at x(Cu)>0.72

Cu–Si phase equilibria have been investigated at compositions greater than 72 at.% Cu by X-ray diffraction, optical and electronic microscopy, electron probe microanalysis and differential thermal analysis.The general aspects of the phase equilibria already reported in literature have been substantially confirmed, but selected composition ranges and the nature of a few invariant equilibria have been modified. In particular stability ranges of the β, δ and η phases have been slightly modified as well as temperature and nature of the invariant equilibria related to the γ ? δ transformation.Stability of the ?-(Cu₁₅Si₄) phase has been especially investigated concluding that it is thermodynamically stable but kinetically inhibited by nucleation difficulties which become especially effective when samples are synthesized in very high purity conditions.Crystal structure and composition ranges of the high temperature β and δ phases, despite difficulties by the non-quenchability of these phases, have been investigated by different methods including high temperature XRD.     

Investigation of Fe-1.0% Cu surrogate specimens with nonlinear ultrasound

This research explores the sensitivity of nonlinear ultrasound (NLU) to the changes in microstructure of heat treated Fe-1.0 at.% Cu binary alloy. Results from experimental measurements and a theoretical model each show that the acoustic nonlinearity parameter, β increases with increasing Cu-precipitate radius. The iron-copper material investigated in this research serves as a surrogate material to simulate the evolution of radiation damage as a result of copper nanocluster precipitation that occurs in reactor pressure vessels (RPV) of light water nuclear power reactors. With RPVs seeing more neutron cycles than originally anticipated, it is imperative to develop nondestructive evaluation (NDE) techniques capable of evaluating the integrity of these structures.     

铸态Mg-2Zn-1.5Cu合金组织及力学性能

利用金相显微镜、扫描电镜、透射电镜、XRD物相分析以及力学性能测试等手段,研究了Mg-2Zn-1.5Cu(at%)合金的显微组织及力学性能。结果表明:铸态合金存在较为明显的元素偏析,主要的第二相为MgCuZn相;合金的力学性能随着温度的提高而不断降低,塑性变化幅度要明显高于强度,合金的断裂方式也由低温时的沿晶断裂转变为高温时的穿晶断裂;在相同温度下,随着应力的提升,合金的稳态蠕变速率提高,蠕变机制由晶界控制转变为晶界及位错共同控制;在相同的应力下,随着温度的提升,合金的稳态蠕变速率存在数量级的提升,蠕变激活能由130kJ/mol降低到36.4 kJ/mol;在200℃,45 MPa时,出现加速蠕变阶段,发生蠕变断裂,断口存在明显的穿晶断裂特征,基体中有大量的沿基面运动的位错,部分位错发生攀移,MgZnCu相具有减缓蠕变变形的作用。     

Enhancement of the fracture toughness of bulk L12-based (Al+12.5 at.% M)3Zr (M=Cu,Mn) intermetallics synthesized by mechanical alloying

The microstructural evolution and the mechanical properties of L1₂-type bulk (Al+12.5 at.% M)₃Zr (M=Cu, Mn) intermetallic compounds with a nanocrystalline structure were investigated. The (Al+12.5 at.% M)₃Zr (M=Cu, Mn) powders synthesized by planetary ball milling (PBM) could be successfully consolidated into nearly pore-free bulk compacts at 580 and 620 °C without taking holding time by spark plasma sintering (SPS). Their grain sizes were in the range from 8 to 10 nm. The micro-hardness of the SPS-processed bulks was measured to be 975.8 and 983.9 Hv, respectively. On the other hand, their fracture toughness was barely ∼2 MPam^1/2. It was lower than those (∼4–6 MPam^1/2) of the coarse-grained (∼100 nm) bulk specimens annealed. This result indicates that a grain refinement towards the nanoscale does not have an appreciable effect on improving fracture toughness in brittle intermetallics. Thus, it was found that the fracture toughness could be enhanced by proper annealing and addition of the boron. Furthermore, the effect of grain size on the fracture toughness in nano-sized level was investigated in the bulk specimen prepared by arc melting, using mechanical alloying powders with ball-milling.     

烧结钕铁硼(Al+Cu)含量对晶界扩散的影响

本研究对(Al+Cu)含量分别为0.25%的钕铁硼基体和0.5%基体进行Dy晶界扩散,并分析了矫顽力、Dy含量分布和微观结构。通过比较两种磁体的成分、性能发现,在Dy增加量基本相同的情况下,高(Al+Cu)磁体扩散后的矫顽力提高量相较于低(Al+Cu)磁体高37kA/m~43kA/m。进一步进行成分、矫顽力的梯度分析发现,基体的(Al+Cu)含量变化并没有改变扩散后磁体内部Dy元素随扩散深度的浓度分布,但是矫顽力梯度分析结果显示高(Al+Cu)的各片层矫顽力提升量均比低(Al+Cu)片层高40 kA/m~80 kA/m。后续的EPMA的Dy面分布图显示,高(Al+Cu)基体扩散后Dy在晶界处富集条纹更清晰、连续,而TEM的EDX分析结果也显示高(Al+Cu)样品中晶界附近Dy含量更高。(Al+Cu)含量的提高,使得晶界相的流动性增强,Dy更加连续包裹主相晶粒,使得Dy增加量相同的情况下进一步提升矫顽力。     

纳米铝颗粒增强Sn1.0Ag0.5Cu钎料性能及机理

通过机械混合的方法，制备Sn1.0Ag0.5Cu-xAl复合钎料.采用DSC、STR-1000型微焊点强度测试仪及SEM，研究了纳米铝颗粒对低银Sn1.0Ag0.5Cu钎料组织与性能的影响.结果表明，微量纳米铝颗粒的添加对钎料的熔化温度影响较小，其熔点均在226.9~229.0℃之间.随着纳米Al元素含量的增加，钎料的润湿角逐渐减小，力学性能逐渐增加，当纳米Al元素的添加量为0.1%时，焊点的拉伸力达到最大，为7.1 N.此外，Sn1.0Ag0.5Cu-0.1Al钎料的内部组织得到显著细化，焊点界面金属间化合物的生长也得到明显抑制，主要归因于纳米颗粒对金属间化合物生长的吸附作用.     

Sn-3.5Ag-1.0Zn/Cu界面微观组织演变及接头力学性能

研究了Sn-3.5Ag-1.0Zn/Cu界面微观组织结构的演变过程,对接头在不同老化阶段的力学性能进行了测试.结果表明,Zn的添加不影响界面初生相的成分和组成,初始化合物层仍然为扇贝状Cu6Sn5.但在随后的热老化阶段,Cu3Sn受到抑制,取而代之的是Cu5Zn8化合物层.正是由于Cu5Zn8的形成,化合物层在老化阶段的生长变得缓慢.由于Cu5Zn8与Cu6Sn5的力学性能差异较大,Sn-Ag-Zn/Cu接头的剪切强度低于Sn-Ag/Cu接头.随着化合物层的生长,剪切强度逐渐减小,断口区域也从钎料转向化合物层中.     

Microstructures and properties of 1.0%Al2O3/Cu composite treated by rolling

The 1.0%Al2O3/Cu （mass fraction） composite was prepared by hot pressing （HP）, then treated by rolling to get a full density. The microstructures and the micro area element distribution of the composite were analyzed by SEM. The density, electric conductivity and tensile strength were also investigated. The experimental results show that the alumina particles are more dispersed and become smaller through a single-pass rolling. The pore existing in the composite is eliminated or closed under the rolling force. The relative density increases from 98.4% to 99.2%. The electric conductivity increases from 88.9%IACS to 91.2%IACS. The tensile strength is increased by 47% from 300 MPa to 440 MPa.     

(TiB2+Al3Ti)/Al-4.5Cu原位复合材料的高温耐磨性能

本文采用混合盐法制备了(TiB2 Al3Ti)/Al4.5Cu原位复合材料,研究了该复合材料在150℃下的干摩擦滑动磨损行为,并与基体合金进行对比.结果表明,载荷在10～20 N之间时,(TiB2 Al3Ti)/Al-4.5Cu原位复合材料的磨损量低于基体合金,但并不明显;随载荷的增加(特别是当载荷超过30 N之后),复合材料的磨损量仍低于基体合金,且复合材料的磨损量增大的速度小于基体合金磨损量的增长速度.(TiB3 Al3Ti)/Al-4.5 Cu原位复合材料同45钢对磨时的主要磨损机制为粘着磨损和磨粒磨损.随着原位反应体系中混合盐含量的增加,复合材料的耐磨性能提高,并逐渐由粘着磨损向磨粒磨损过渡.     

A study on the microstructure of D023 Al3Zr and L12 (Al+12.5 at.% Cu)3Zr intermetallic compounds synthesized by PBM and SPS

The spark plasma sintering (SPS) of L1₂ phase Al₃Zr and (Al+12.5 at.% Cu)₃Zr powders with a nanocrystalline microstructure has been studied to produce bulk intermetallic compounds which maintain metastable structures such as L1₂ structure and nanocrystalline microstructure. The powders were prepared by 10 h planetary ball milling (PBM). Full-density L1₂ (Al+12.5 at.% Cu)₃Zr intermetallic compounds were obtained by SPS for 0 min at 600 °C. The specimens prepared with a longer holding time than 0 min at 600 °C or a higher temperature than 600 °C had local melting areas where micro-cracks were found. They had a lower relative density than the specimen SPS sintered at 600 °C for 0 min. The smallest grain size was obtained in the specimen prepared at 600 °C for 0 min, which was 20–30 nm as confirmed by TEM observation. This was the smallest grain size ever reported in the trialuminide specimens processed by various consolidations of nanocrystalline powders. Accordingly, the highest micro-hardness, 989.5 H_V, was obtained in the specimen and this value was three times higher than those of the specimens with micro grain sizes. Full density Al₃Zr intermetallics were prepared by SPS at 700 °C for 0 min. However, their crystal structure was D0₂₃ and micro-hardness was 778.1 H_V. By using SPS, the sintering time can be reduced within 10 min. It was thought that the decrease in sintering temperature for the PBM Al₃Zr and (Al+12.5 at.% Cu)₃Zr powders by 200–300 °C compared with the conventional sintering temperature resulted in the refinement of microstructure to the nano-size level.     

Boundary trend of α1/(α1 +α2) phase region at lower Cu side in Al-Zn-Cu system

The range of miscibility gap above 300 ℃ at low Cu side in Al-Cu-Zn ternary system was obtained by EPMA of the designed alloys and diffusion-couples treated for equilibrium. The results about the boundary trend of the α1 / (α1 α2 ) phase region was obtained. The α1 / (α1 α2 ) boundary moves towards the lower Zn side with the increase of Cu content. The results are opposite to traditional phase diagrams obtained by experiments, but consistent with recent thermodynamic calculations.     

Enthalpies of Formation of (Cu,Ni)3Sn, (Cu,Ni)6Sn5-HT and (Ni,Cu)3Sn2-HT

Standard enthalpies of formation of ternary phases in the Cu-Ni-Sn system were determined along sections at 25, 41 and 45.5 at.% Sn applying tin solution drop calorimetry. Generally, the interaction of Ni with Sn is much stronger than that of Cu with Sn. Along all sections the enthalpy of formation changes almost linearly with the mutual substitution of Cu and Ni within the respective homogeneity ranges. Thus no additional ternary interaction promoting the formation of further Cu-Ni-Sn phases can be assumed. The results are discussed and compared with literature values relevant to this system.     

溶胶-凝胶法制备高稳定性Mg_xNi_(1.0)Mn_(2-x)O_4系列热敏电阻

采用溶胶-凝胶(Sol-Gel)技术制备MgxNi1.0Mn2-xO4(x=0,0.1,0.2,0.3,0.4)系列超细氧化物热敏粉体,并经成形,烧结等工艺制得性能优异的负温度系数热敏电阻。采用热分析系统、X射线衍射(XRD)仪、扫描电子显微镜(SEM)和HP34401型数字电压表分析MgxNi1.0Mn2-xO4氧化物热敏粉体的热处理过程、烧结体的显微结构和电性能。结果表明:在700℃热处理,得到尖晶石结构的MgxNi1.0Mn2-xO4氧化物热敏超细粉体。在空气气氛下,1200℃烧结2h,得到尖晶石结构的MgxNi1.0Mn2-xO4氧化物烧结体,烧结体显微结构致密。随着镁离子含量的增加,MgxNi1.0Mn2-xO4氧化物烧结体电阻值和材料常数增大,材料常数B≥3900,老化稳定性有很大提高。