银粉形貌及粒径对银浆性能的影响

将银粉、有机载体和玻璃粉按一定比例混合制成导电银浆。银浆通过丝网印刷在硅基片上,保温烧结。采用SEM、四探针法研究银粉的不同粒径与形貌对银浆烧结厚膜层方阻的影响。结果表明,随着球形银粉粒径增大,银膜方阻先减小后增大,当球形银粉粒径在2μm时银膜方阻最小,为4.44?/□;当2μm片状银粉和2μm球形银粉混合加入时,银膜方阻最小,为3.95 m?/□;随着片银的含量增加,银膜方阻先减小后增大,当片状银粉为50%时银膜方阻最小,为3.92 m?/□。     

中温快烧银浆表面亮度的影响因素

银层不亮是中低温烧结银浆经常出现的问题。研究了乙基纤维素、玻璃、添加剂及银粉对烧结银层发红的影响。结果表明,乙基纤维素的灰分和玻璃中的重金属氧化物是导致烧结银层发红的重要原因。优化配方使用混合银粉,加入复合添加剂和氧化剂,选用合适的玻璃粉,所得银浆料快速烧结,银层表面白色光亮、致密,其粘度、印刷性能、方阻、附着力等各项指标符合要求。     

太阳能电池导电银浆的烧结工艺研究

研究了不同烧结温度和保温时间下烧结对银膜附着力和方阻的影响,用扫描电镜观察烧结后银膜的形态。结果表明,在850℃烧结保温40 s得到的银膜性能较优,银膜的附着力和方阻分别为3.193 N和4.16 m?/□。     

陶瓷电容器镍电极的致密化过程

分别在550、650、750和950℃的烧结温度下制备陶瓷电容器贱金属镍电极.研究了烧结温度对镍电极附着力和方阻的影响,分析了不同烧结温度下镍电极的微观组织和成分,揭示了镍电极致密化过程的本质.结果表明,随着烧结温度的增加,镍电极附着力逐渐增大,方阻逐渐下降;烧结温度是影响镍电极致密化过程的重要因素,950℃时形成了连续、致密的三层结构电极,中间层与镍电极附着强度相关;镍电极的致密化过程分为液态玻璃的生成、镍粉颗粒的溶解-析出和固相骨架的形成3个阶段.     

银膜在玻璃基体上烧结过程的微观结构分析

研究了银膜在各温度下烧结的微观结构变化,讨论了影响膜层致密的。还描述了颗粒和孔隙长大及致密化过程,发现在600－700℃银膜出现分布均匀的针眼透光现象,主要是银粉的过度收缩及液相玻璃体对银颗粒的拉附对银膜的整体性影响。     

导电银浆在铝合金表面的烧结性能分析

制备一种用于铝合金表面烧结银厚膜的低温烧结型导电银浆,以解决铝合金的软钎焊问题. 采用熔融淬火方法制备玻璃化转变温度(T_g)为360 ℃的Bi₂O₃-B₂O₃-ZnO玻璃粉. 将玻璃粉、亚微米银粉和有机载体混合制成无铅低温烧结型银浆,将该银浆涂覆在6061铝合金表面,并在440,470,500,530 ℃的温度下进行烧结. 研究烧结温度对银厚膜的电阻率、可焊性及与基板结合强度的影响. 当玻璃粉与银粉重量比为1∶9,烧结温度为530 ℃时,烧结银厚膜的电阻率为2.2 μΩ·cm,抗剪强度为56.0 MPa;同时Al,Mg和Bi₂O₃发生氧化还原反应在银厚膜与铝基板界面产生纳米级Bi单质,进而实现冶金结合. 结果表明,提高烧结温度可以有效促进玻璃的润湿铺展、Ag颗粒之间的颈缩和Ag颗粒的生长,进而明显改善银厚膜软钎焊可焊性.     

烧结温度对(AlCoCrFeNi2.1)p/Cu复合材料组织和性能的影响

通过放电等离子烧结技术制备了高熵合金增强Cu基复合材料,研究了烧结温度对复合材料的组织结构与性能的影响。结果表明,高熵合金颗粒在Cu基体中分散相对均匀,与Cu基体结合良好。随着温度升高,结合方式由机械结合为主逐渐转变为扩散结合为主,Cu沿着BCC相扩散进入高熵合金;复合材料的致密度随着温度的升高呈现先增加后降低的趋势;800℃下制备的复合材料硬度(HBW)最高为60.43,致密度为98.4%,电导率为39.09 MS/m。     

银粉粒径及形貌搭配对无铅导体浆料性能的影响

从银粉的不同粒径级配与形貌搭配方面考察其对无铅导体银浆烧结后膜层的电阻率、附着力的影响。选取了平均粒径分别为0.1,0.4,1μm的球形银粉以及平均粒径为3~6μm的片状银粉,首先将3种粒径的球形银粉按不同比例的搭配得到3种球形银粉最紧密堆积的最佳比例,然后根据Dinger-Funk粉体堆积原理进行验证,最后再与片状银粉搭配制得导电银浆。实验结果表明,在大颗粒间填充小颗粒能增加粉体堆积的致密度,从而明显降低烧结后膜层的方阻,同时通过在片状银粉之间空隙填充这种致密度好的球形混合银粉颗粒,比单纯使用片状银粉制得的银膜层方阻更低。通过本次实验制得的银膜外表致密光洁,可焊性、耐焊性良好,方阻为3.78 m?/□、附着力40 N/mm~2。     

放电等离子烧结制备TiC/双相不锈钢复合材料的致密性及显微组织

采用放电等离子烧结(SPS)方法,制备了Ti C/铁素体奥氏体双相不锈钢复合材料。通过密度仪、XRD、SEM和EDS等技术,研究了Ti C含量和烧结温度对Ti C/双相不锈钢复合材料致密性和显微组织的影响。结果表明:采用SPS方法能在较低温烧结温度下获得高致密度的Ti C/双相不锈钢复合材料,且其相对密度随着Ti C含量的升高或烧结温度的降低而减小。在850~950℃烧结温度区间,有碳化物沿晶界析出,通过高温热处理能使有害碳化物回溶,同时有利于Ti C颗粒与不锈钢基体界面的进一步结合。     

低温烧结型银浆料对半导体芯片贴装性能的影响

研究低温烧结型银／玻璃体系浆料的成分配比、制备工艺及其半导体芯片贴装烧结工艺,探讨浆料中银粉、玻璃粉和有机载体的成分对浆料烧结体的微观组织、热导率、线膨胀系数及芯片组装的剪切力之间的影响关系,利用理论模型计算浆料烧结体的热导率和线膨胀系数,分析其理论计算值与实测值差异的影响因素。结果表明：随着玻璃粉含量的增加,浆料烧结体的线膨胀系数及热导率逐渐降低,当银粉和玻璃粉的质量比为7：3,固体混合粉末与有机载体的质量比为8：2时,芯片贴装后可满足热导率和线膨胀系数性能的要求,同时所承受的剪切力最大。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.