Measurements of liquidus temperatures in the Cu-Nb and Cu-Cr systems

The Cu-Nb and Cu-Cr alloys at compositions ranging from 5 to 86 wt% Nb (89 wt% Cr) were processed in a clean environment and solidified at relatively low cooling rates of 50 to 75 °C/s to determine liquidus temperatures. In this study, both temperature measurements and microstructural observations confirmed the equilibrium phase diagram having an S-shaped, nearly flat liquidus, rather than that with a monotectic reaction in the liquid state. However, a metastable liquid miscibility gap exists in the two systems.     

Calculation and application of liquidus projection

1. Introduction Liquidus projection is one of the important types of phase diagrams. Ternary liquidus projection at constant pressure onto a compositional plane is the most commonly used type. It shows the phase rela- tionships between the liquid phase and the other phases. With the isothermal contour lines on the liq- uidus projection, a ternary liquidus projection gives a direct visualization of the liquidus surface. Rhines [1] presented in detail many ternary liquidus projec- tions. It is …     

Electrodeposition and characterization of Cu-Nb composite coatings

Copper coatings containing well-distributed Nb particles were obtained by co-electrodeposition in an acidic sulfate bath. Nb particle concentration in the bath was the most significant factor for the incorporation of Nb particles in copper, followed by stirring rate, whereas current density presented low significance. High Nb particle concentration and low stirring rate led to a higher incorporated Nb particle content. The microhardness of the composite layers was higher than that of pure copper deposits obtained under the same conditions due to copper matrix grain refinement and increased with the increase of both current density and incorporated Nb particle volume fraction. The corrosion resistance of Cu-Nb composites in 0.5 wt.% H₂SO₄ solution at room temperature was higher than that of pure copper and increased with the increase of the Nb content.     

Microstructures and liquidus projection of the ternary Ag-Sb-Te system

Ag-Sb-Te alloys are important for thermoelectric applications. Fifty-one Ag-Sb-Te ternary alloys were prepared, and their primary solidification phases were analyzed. The liquidus troughs of the liquidus projection of the ternary Ag-Sb-Te system are determined based on the experimental results and the phase diagrams of the three binary constituent systems. There are 13 primary solidification phase regions. In addition to the three terminal solid solution phases and nine binary compounds, there is one ternary compound, AgSbTe₂. A unique microstructure with bright spherical phases uniformly dispersed in a matrix caused by a miscibility gap in the liquid phase is found in the γ-Ag₂Te primary solidification phase regime. A very fine microstructure with nanometer size Ag₂Te is also observed, resulting from the class I reaction, liquid = δ + Ag₂Te + AgSbTe₂, at 496.5 °C, and the liquid composition of Ag-40.0 at%Sb-36.0 at%Te.     

Measurements of the melting points,liquidus, and solidus of the Mo,Ta, and MoTa binary alloys using a novel high-speed pyrometric technique

The measurement of high phase-transition temperature is equally challenging and useful for developing high-temperature materials for critical applications. Pyrometer is a suitable option to measure the phase-transition temperature above 2300 K. In this work, Mo, Ta, and their isomorphous binary alloys are selected as the target system for high-speed pyrometer temperature measurements in the arc-melting setup. The present phase transitions (melting point, solidus, and liquidus) measurements indicate that the MoTa is an isomorphous system with a narrow freezing range (i.e., an average value < 35 K). The results from this present work would change the existing MoTa phase diagram. The Gibbs energy modeling for liquid (L) and BCC_A2 (α) phases of the MoTa system are then performed, including the latest experimental results from this work. The applications of the current experimental methodology could be extended to measure the high phase-transition temperatures in superalloys with significant commercial values.     

Effect of HT on the Interface Diffusion and Microstructure of Cu-Nb Micro-composites

We have fabricated high strength and conductivity Cu-Nb micro-composites by bundling and drawing process. The interface diffusion and microstructure of Cu-17vol% Nb composites experienced severe plastic deformation at different heat treatment conditions are investigated. Diffusion at Cu/Nb interface of Nb filaments is observed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The interface characteristic and edge spheroidization of Nb filaments are discussed.     

Determination of the liquidus of the ternary system Cu-Sn-Ti

The liquidus surface of the ternary system Cu-Sn-Ti was established by determining the primary crystallizing phases as well as the phase reactions involving the liquid phase. The τ ₁CuSn₃Ti₅ and Ti₆Sn₅ have a wide field in terms of the primary composition. The primary crystallization of the τ ₂CuSnTi phase was observed in alloys containing 26 or more at.% Sn and up to 10 at.% Ti. In the tin-rich corner, the liquid phase solidifies in a ternary eutectic reaction.     

Determination of the liquidus of the ternary system Cu-Sn-Ti

The liquidus surface of the ternary system Cu-Sn-Ti was established by determining the primary crystallizing phases as well as the phase reactions involving the liquid phase. The τ ₁CuSn₃Ti₅ and Ti₆Sn₅ have a wide field in terms of the primary composition. The primary crystallization of the τ ₂CuSnTi phase was observed in alloys containing 26 or more at.% Sn and up to 10 at.% Ti. In the tin-rich corner, the liquid phase solidifies in a ternary eutectic reaction.     

形变与时效Cu-Cr合金的研究进展

综述了国内外形变与时效Cu-Cr合金的研究现状和最新进展,主要包括形变与时效Cu-Cr合金的特点和性能;形变与时效Cu-Cr合金的优缺点及研究现状.如拉拔法、冷轧法、锻造法、挤压法等.在综述的基础上,简要讨论了形变与时效Cu-Cr合金未来的发展动向.     

Cu-Cr原位复合材料组织性能研究

采用感应加热熔炼及通过热锻和线拉变形结合中间热处理制备了Cu-15％Cr原位复合材料，用SEM和TEM等技术对形变Cu—Cr原位复合材料的Cr纤维形成过程、立体形态进行了分析。结果表明，在变形过程中Cr树枝晶发生转动，平行于线轴方向排列；Cr纤维立体形态则为卷边的薄片状。测定了形变Cu—Cr原位复合材料的抗拉强度，分析表明，强度随变形量的增加而提高，与纤维相间距呈Hall—Patch关系。     

Cu-Cr原位复合材料组织性能研究

采用感应加热熔炼及通过热锻和线拉变形结合中间热处理制备了Cu-15%Cr原位复合材料,用SEM和TEM等技术对形变Cu-Cr原位复合材料的Cr纤维形成过程、立体形态进行了分析.结果表明,在变形过程中Cr树枝晶发生转动,平行于线轴方向排列;Cr纤维立体形态则为卷边的薄片状.测定了形变Cu-Cr原位复合材料的抗拉强度,分析表明,强度随变形量的增加而提高,与纤维相间距呈Hall-Patch关系.     

Effect of Annealing on the Microstructure and Properties of In-situ Cu-Nb Microcomposite Wires

The effects of annealing on microstructure,magnetoresistance,and hardness of an in situ Cu-Nb microcomposite wire have been investigated.Neither changes in microstructure nor hardness were found until 500 ℃.Particularly,microstructural change within the Nb films was observed in the annealed samples.The room-temperature magnetoresistivity was almost negligible,while magnetoresistivity at-196 ℃ increased with magnetic field.At temperature above500℃,recovery and recrystallization occurred,and both the resistance and hardness decreased.     

额外纯Cu对Cu-Nb复合线材力学及导电性能的影响

通过拉伸试验和四点测电阻法,对中心含额外纯Cu的Cu-Nb复合线材的力学及导电性能进行测试,并利用SEM观察其微观结构和断口形貌。结果表明:从断口中心到边沿,断裂方式从正断逐渐转向剪切断裂。中间纯Cu有利于导电性和强度的优化。线材的强度随着Nb芯丝间距的减小呈指数上升趋势。当间距小于100 nm时,尺寸效应对强度有显著影响,且77 K下强度随间距减小而增大的速度大于室温下强度随间距减小的速度。而当间距大于300 nm时,尺寸效应对强度的贡献很小。     

自生复合Cu—Cr合金的定向凝固特性

采用定向凝固连续铸造技术成功制备了纤维增强的自生复合Ｃｕ－Ｃｒ合金电车线线坯,并对自生复合Ｃｕ－Ｃｒ合金的定向凝固特性,包括组织形态、枝晶间距及纤维长度等,作了详细的研究。实验结果表明：保持平面状或胞状的凝固界面有利于纤维状的自生复合组织的形成;当ＧＬ＝２１０℃／ｃｍ,Ｖ＝０．６ｍｍ／ｍｉｎ时,Ｃｕ－０．８％Ｃｒ合金凝固界面呈平面状;增加凝固速率,Ｃｕ－Ｃｒ合金的一次枝晶间距呈先增大后减小的规律,     

高强高导Cu-Nb微观复合材料热稳定性

通过集束拉拔技术制备了高强高导Cu-Nb微观复合材料,采用X射线衍射和扫描电镜等手段分析了不同热处理条件下材料晶体取向和界面结构的演变,通过应力应变曲线和电导测试研究了不同热处理条件对材料强度和电导的影响规律,结果表明:700℃热处理就可促使形成Cu、Nb的再结晶织构,由极塑变形所导致的区域化学势差异及原子扩散是影响Cu/Nb界面稳定性的关键因素;而700℃的中间热处理可以极大改善材料后续的加工塑性,同时在一定后续形变量条件下仍可获得高强度性能,而且通过低温调整热处理可改善材料导电性,同时保持较高强度。