Non-Conventional Techniques for the Study of Phase Transitions in NiTi-Based Alloys

Differential scanning calorimetry and electrical resistance measurements are the two most common techniques for the study of the phase transition path and temperatures of shape memory alloys (SMA) in stress-free condition. Besides, it is well known that internal friction measurements are also useful for this purpose. There are indeed some further techniques which are seldom used for the basic characterization of SMA transition: dilatometric analysis, magnetic measurements, and Seebeck coefficient study. In this work, we discuss the attitude of these techniques for the study of NiTi-based phase transition. Measurements were conducted on several fully annealed Ni_50?x Ti₅₀Cu _x samples ranging from 3 to 10 at.% in Cu content, fully annealed at 850 °C for 1 h in vacuum and quenched in water at room temperature. Results show that all these techniques are sensitive to phase transition, and they provide significant information about the existence of intermediate phases.     

Investigation of Al-based Alloys for Brazing SiC_p/Al Composites

The brazing of SiCp/Al composites is limited owing to the unavailability of suitable commercial intermediate temperature brazes. Adding a third constituent of copper to aluminum-silicon brazing alloy can depress the melting point sharply. While, it generates a large volume fraction of the hard Al2Cu intermetallic compounds (IMCs), which makes the alloy brittle and reduces its corrosion resistance. A quaternary addition of nickel that partly substitute for copper can refine grain size significantly, improve the mechanical properties, and without altering the melting range of aluminum-silicon-copper alloy. Al-Cu-Ni-Si braze alloy has been prepared and a fluxless process has been employed to braze SiCp/Al composites that leads to a good bonding strength of brazing joint.     

金首饰用无镉K金钎料的研究与发展

概述了金属镉在金首饰合金钎料中的作用和无镉K金钎料的合金化原理,给出了近年开发的9K~22K颜色和白色无镉K金合金钎料的成分和熔化温度范围,指出:在K金首饰应用领域,开发适合分级钎焊的高性能无镉K金钎料系列以及无镉K金钎料的标准化和商业化,依然是无镉K金钎料的发展方向。     

镍基钎料钎焊不锈钢的钎缝组织及工艺的研究

研究了常用镍基钎料BNi-2钎焊1Cr18Nj9Ti不锈钢的钎缝组织特征和相组成以及采用扩散热处理和加压钎焊工艺对钎缝组织的影响,钎缝宽度对接头性能的影响.研究结果表明,采用合适的扩散热处理和加压钎焊工艺可以有效的消除钎缝组织中的脆性化合物相,合适的钎缝宽度可以提高钎焊接头的物理性能.     

含钪铝锌镁合金铸锭和均匀化显微组织研究

采用金相显微镜、差示扫描量热仪、扫描电镜及其能谱仪研究了Al-5.4Zn-2.0Mg-0.3Mn-0.25Cu-0.1Zr和Al-5.4Zn-2.0Mg-0.3Mn-0.35Cu-0.1Zr-0.25Sc两种合金的铸态及均匀化态显微组织演变与成分分布.结果表明:铸态组织以典型的枝晶结构存在,由过饱和的α-Al固溶体和α-Al+η-MgZn2的非平衡共晶相组成;铸态合金在470℃保温24 h,非平衡共晶相消失,合金枝晶偏析消除.确定合金铸锭的理想均匀化工艺参数为470℃×24 h.     

几种Mg-Zn-Y合金的热力学性能及组织研究

基于Miedema模型混合焓模型外推出4种不同成分的Mg-Zn-Y合金的部分热力学性能,利用实验获得相应成分的合金,并利用XRD及EDS进行物相分析及成分分析。结果表明,合金中各相的形成过程与理论计算结果一致,Zn与Y的生成焓最大,发生反应生成中间相的可能性最大。     

DSC Study on Phase Transitions and Their Correlation with Properties of Overaged Al-Zn-Mg-Cu Alloys

This article investigates the phase transitions of complex quaternary Al-Zn-Mg-Cu alloys with Zr addition at overaged conditions. Differential scanning calorimetry (DSC) is employed to quantitatively analyze the phase transformation phenomena of a wide range of 7xxx series alloys through endothermic and exothermic reactions. The DSC observations detailing heat effect peaks and thermal parameters of ??? dissolution contain valuable information on the presence of equilibrium phases and the optimum alloying element contents. Based on DSC experimental data and phase diagrams, the balance of critical properties such as strength and electrical conductivity of Al-Zn-Cu-Mg 7xxx series alloys has been studied by considering the formation, dissolution, and incipient melting of S and T phase, dissolution of ??? phase as well as the formation of ?? phase. Nine Al-Zn-Mg-Cu alloys have been studied through microstructural examination and detailed DSC analysis. The correlation between the properties and the DSC data of the selected alloys has been analyzed.     

Experimental and Theoretical Determination of Phase Fraction in the Fe-B-V Alloys

In the present work the fraction of equilibrium phases in various Fe-B-V alloys was determined by various methods. Area fractions were determined from pictures of microstructures of alloys by means of software Gwyddion. Fractions were calculated also by lever rule from experimentally determined values. All experimentally determined fractions were compared with equilibrium fractions of phases calculated with software Thermo-Calc. Good agreement between theoretical and experimental values was found. The reason of the study was to verify the parameters for thermodynamics calculations for the Fe-B-V system Homolová et al. (J. Alloys Compd. 520:30-35, 2012).     

Pt-24Ir-RE合金的显微组织与性能研究

通过金相及电子显微镜技术，进行了力学和电学性能实验，研究了添加微量稀土元素La、Sm、Y对Pt-24Ir合金的组织结构与性能的影响。结果表明：稀土元素有效地细化了合金的显微组织结构，并以单质形式均匀析出和弥散分布在合金基体中，从而使合金的综合性能获得改善。     

Al-In难混溶合金的液相分离过程及显微组织数值模拟

建立了一个描述Al In难混溶合金冷却过程中液—液相变区微观组织演化过程的数学模型。该模型综合考虑了第二相液滴的形核、扩散长大、Brownian碰撞和运动碰撞的共同作用 ,并对模拟的结果进行了可视化动态模拟研究。以Al 3 0 %In合金为例进行模拟 ,结果表明 ,第二相在断面上的体积分数、粒子大小及分布与实验结果基本一致。这说明建立的模型对Al In难混溶合金具有一定实际预测功能。     

热型连铸Ag-Cu-Zn合金工艺及其组织

在自制的水平式热型连铸设备上,选用合适的工艺参数制备出了表面质量良好、内部组织沿轴向均匀分布的Ag-Cu-Zn合金铸棒.     

Microstructure,Phase Occurrence,and Corrosion Behavior of As-Solidified and As-Annealed Al-Pd Alloys

In the present work, we studied the microstructure, phase constitution, and corrosion performance of Al₈₈Pd₁₂, Al₇₇Pd₂₃, Al₇₂Pd₂₈, and Al₆₇Pd₃₃ alloys (metal concentrations are given in at.%). The alloys were prepared by repeated arc melting of Al and Pd granules in argon atmosphere. The as-solidified samples were further annealed at 700 °C for 500 h. The microstructure and phase constitution of the as-solidified and as-annealed alloys were studied by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction. The alloys were found to consist of (Al), ε _n (~ Al₃Pd), and δ (Al₃Pd₂) in various fractions. The corrosion testing of the alloys was performed in aqueous NaCl (0.6 M) using a standard 3-electrode cell monitored by potentiostat. The corrosion current densities and corrosion potentials were determined by Tafel extrapolation. The corrosion potentials of the alloys were found between ? 763 and ? 841 mV versus Ag/AgCl. An active alloy dissolution has been observed, and it has been found that (Al) was excavated, whereas Al in ε _n was de-alloyed. The effects of bulk chemical composition, phase occurrence and microstructure on the corrosion behavior are evaluated. The local nobilities of ε _n and δ are discussed. Finally, the conclusions about the alloy’s corrosion resistance in saline solutions are provided.     

TiZrFe钎焊料熔点及焊接组织研究

本文在TiZrFe共晶合金的基础上,研究了用Cu、Ni替代Fe对钎料熔点及组织结构的影响。研究结果表明,成分为Ti55Zr20Fe10Ni10Cu5的钎料的熔点最低,为846．1℃。通过快淬工艺将该钎料制成非晶带材,制得的非晶带钎料在真空条件下与母材Ti-6Al-4V进行焊接,用SEM观察钎焊区组织。发现需要在900℃下保温20min可获得较好的焊接组织。     

Interfacial Bonding Strength Between Brazing Alloys and CVD Diamond

Three groups of brazing alloys were compared in brazing chemical-vapor-deposited (CVD) diamond, including two nickel-based alloys (Ni-3Fe-7Cr-3B-0.5Si-0.02C and Ni-14Cr-10P-0.02C), one copper-based alloy (Cu-10Sn-15Ti), and two silver-based alloys (Ag-5Cu-1Al-1.25Ti and Ag-34.25Cu-1In-1.75Ti). The nickel-based alloys catalytically transformed the sp³-bonded diamond into sp²-bonded carbon during high-temperature brazing operation though with the existence of Cr as the active metal. The bonding strength was very low and the fracture primarily propagated through the sp²-bonded carbon. For Cu-10Sn-15Ti brazing alloy, the transformation of the sp³-bonded diamond into sp²-bonded carbon during high-temperature brazing operation was marginal. The bond strength was adequate and fracture took place primarily through the brazing alloy bulk, due to the high concentrations of Sn and Ti that caused the precipitation of abundant intermetallic compounds in the brazing alloy bulk. For Ag-based alloys having very low concentrations of Ti, no visible degradation of diamond was observed and the bonding strength was very high. Crack primarily propagated through the brazed interface or even the CVD diamond bulk.     

钛合金用钛基焊料的现状及发展

钛及钛合金具有优良的比强度和耐蚀性，在航天航空及石油化工行业中起着重要作用。钎焊作为一种精密成型的焊接方法，在形状复杂和薄壁零件连接中获得广泛应用。本文介绍了钛合金用的钛基钎焊料的发展现状，重点评价了钛基钎料钎焊后组织与力学性能的关系，以及钛基钎料的高温力学性能、耐蚀性以及疲劳性能等。提出了钛基钎焊料仍存在的问题和发展方向。     

Experimental Investigation of Phase Equilibria in Zr-Ni-Pt System

Phase equilibria in Zr-Ni-Pt ternary system have been experimentally determined through diffusion triple and alloy sampling approaches. Based on the results of Electron Probe Microanalysis (EPMA) and x-ray diffraction (XRD), isothermal sections of this system were constructed at 1073 and 1173 K. A new ternary phase denoted as Zr₄(Pt,Ni)₃ was detected with composition ranging from 2.5 to 29.7 at.% Ni and 40.7 to 12.7 at.% Pt at 1073 K while 2.2 to 25.1 at.% Ni and 40.9 to 17.5 at.% Pt at 1173 K, respectively. Three continuous solutions are formed between binary compounds ZrNi and ZrPt, Zr₇Ni₁₀ and Zr₇Pt₁₀, ZrNi₃ and ZrPt₃, and large ternary solubility of Ni in ZrPt₄, and of Pt in Zr₂Ni and ZrNi₅, were observed.     

Microstructure of Iron-Sulfur Alloys

The distribution of sulfur in iron was found to be dependent upon the time and temperature of the treatment as well as the chemical composition of the sulfide. With higher temperatures, the sulfide phase spreads more extensively between the iron grains. A complete network, however, does not form until approximately 1300°C (2372°F), at which temperature the dihedral angle approaches zero. Silicon has little effect on this change. Aluminum, oxygen, and manganese all modify the temperature of sulfide network formation to a higher value. The microstructures which result and have significance in relation to hot-shortness are discussed.     

Al—Si基钎料的液体轧制

利用自制的内水冷双辊急冷设备在大气中分别将Al-Si12.7和Al-Si10-Cu4-Zn7-RE由液态直接一次制成厚度为0.1～0.3mm的薄带钎料,观察了薄带的金相组织,测定了其抗拉强度和塑性指标,并与普通晶态钎料作了比较分析。     

Pt-Ir-Ru合金的性能及显微结构

研究了固溶体范围的Pt-Ir-Ru合金的性能,结果表明：Ru和Ir对Pt-It和Pt-Ru合金的力学性能、电阻率和晶粒尺寸有大的影响。研究的合金有高的电阻率,这是由于铂族金属d－层电子散射、原子半径、电子结构和浓度引起。