The Cu-4Sn and Cu-4Sn-0.15P alloys with rod diameter of 12.5 mm were prepared and then cold drawn to 2.6 mm via multi-pass drawing. The microstructure evolutions, mechanical properties, and electrical conductivity of Cu-4Sn and Cu-4Sn-0.15P alloys were comprehensively analyzed using optical microscope, scanning electron microscope, tension test and electrical conductivity tester. As compared with the P-free alloy, the addition of P can form a new kind of P-rich phase in the Cu-4Sn alloy, and thus refine the casting microstructure via pinning the grain boundary. The toughening mechanisms of P-rich phases in Cu-4Sn-P alloy wires during cold drawing were investigated. With accumulative drawing strain, the spherical P-rich phase gradually changes into fibrous phases, which thus introduce obvious fiber reinforced strengthening. In addition, the distribution of P-rich phase also enhances the< 111 > texture, and promotes the growth of fragmentation zone. It contributes to an improved ultimate tensile strength and final elongation from 664.5 MPa and ∼ 0 % in Cu-4Sn alloy to 970.5 MPa and 1.53 % in Cu-4Sn-0.15P alloy. Finally, the conductivity for Cu-4Sn-0.15P decreases slightly owing to the intensified electron scattering with high amount of primary phase after the addition of P element.

薄壁纯铜热管由于其优异的导热能力而广泛应用于具有高热流密度的微型电子器件产品中.然而,在弯曲变形时管壁外侧的"橘皮"状表面粗化问题成为了热管产品使用的瓶颈.针对薄壁烧结纯铜热管弯曲表面"橘皮"缺陷,采用扫捕电镜(SEM)、白光干涉、电子背散射衍射(EB-SD)等方法分析了"橘皮"部位的宏观形貌、三维轮廓、面粗糙度以及管壁内微观组织及晶体取向分布,并讨论了杂质元素磷对表面粗糙程度的影响.结果 表明:经过烧结处理后,热管壁晶粒长大至壁厚尺度,并形成强烈的Goss型再结晶织构;热管中残留的退火孪晶则具有明显的Cop-per取向,呈条带状贯穿在基体晶粒中;这种取向差异导致弯曲时表面晶粒间无法协调变形,条带状的孪晶严重阻碍位错滑移,造成表面凹凸起伏;微量杂质磷对热管表面橘皮缺陷有明显的影响,随着磷含量的增加,表面粗糙度数值逐渐增大,表面起伏和橘皮缺陷更加明显.

A series of novel Cu-2Ag-xLa alloys with reinforced mechanical properties and enhanced electrical conductivities are developed. The effects of La addition on the microstructural features and mechanical properties of as-cast and solution treated Cu-2Ag alloys are systematically investigated. The yielding strength of as-cast Cu-2Ag alloys with 0.02La and 0.07La (wt.%) is considerably reinforced by relative amounts of 55.56% and 30.16%, respectively. The strengthening mechanism for such increased yielding strength is mainly related to the shifting of interfacial relation between matrix and Ag-rich phase from original semi-coherent type to non-coherent type with La doping. Consequently, the interface barrier strength is enhanced by the non-coherent interface, and contributes to the increased yielding strength. Meanwhile, the strengthening effect from La addition closely depends on the exact contents of La element. As La content increases from 0.02 to 0.07 (wt.%), the strengthening effect becomes weaker because of the increased space of Ag-rich phases leading to an 16.33% decrease in yield strength. Additionally, La has dual effects on the dissolution of Ag-rich phases and precipitation of new La-rich phase in the as-cast alloys during solution treatment. Simultaneously, the precipitation of the La-rich phase abnormally enhances the electrical conductivity of the solution La-containing alloys when the solution time exceeds 24 h.

The evolution of microstructure, textures, and mechanical properties of thin-walled copper tube during heat treatment was investigated using EBSD technique and tensile test. The results show that the initial deformation textures of pre-drawn thin-walled copper tube are mainly composed of Copper and Y components, while with the increase of temperatures, the textures are transformed into a strong Goss texture gradually. The high-resolution microstructural characterizations indicate that the new Goss recrystallized grains nucleate and grow up within the deformed Copper grains and Y grains in different mechanisms, respectively. The tensile strength of the thin-walled copper tube decreases gradually with the increase of the temperature, while the elongation increases first and then decreases sharply due to the action of grain sizes and texture components.

A new Cu-2 wt% Ag-0.15 wt% La alloy composed of large-size Ag-rich primary phases was processed into wire billets by successive drawing, annealing and continuous extrusion forming (CONFORM). The microstructural evolution and mechanical properties of the samples obtained by drawing, annealing and CONFORM were then investigated. The results indicate that a desirable combination of high ultimate tensile strength (300 MPa) and elongation (49.5%) was obtained after CONFORM. The latter allowed the microstructure to be significantly refined via an almost full dynamic recrystallization (DRX), with grain sizes of similar to 1 mu m. In addition, the large-size primary phases were broken into dispersed nanophases with an average size of 800 nm. The dispersed phases promoted the DRX of the matrix via particle-stimulated nucleation. As a result, the enhanced toughness (11145.98 MPa.%) is contributed by grain refinement and dispersion strengthening of the nanosized phases.

A new Cu-2Ag-0.14La alloy is developed to enhance the mechanical property and electrical conductivity with inducement of Ag-rich primary phases and finer nanoscale Ag precipitates. The microstructural evolution and mechanical properties of Cu-2Ag-0.14La and Cu-2Ag alloys obtained by drawing and annealing were then summarized and analyzed. The results indicate that both the yielding and ultimate tensile strengths of annealed Cu-2Ag-0.14La alloy were reinforced after La modification. The average grain sizes of two alloys increase during annealing, but the size ratio (RCu-2Ag-0.14La/RCu-2Ag) dramatically varies with rising the heat temperature, evolving from 70.48% at 400 degrees C to 43.78% at 650 degrees C. Meanwhile, it is found that the refined grains sizes in Cu-2Ag-0.14La alloy are closely related to the nano-scale precipitates (similar to 450 nm), which hinder the formation of subgrain boundaries at 400 degrees C, and impose a stronger pinning effect on boundary migration of recrystallized grains during annealing (>= 450 degrees C). Consequently, higher hardness and electrical conductivity are contributed by grain refinement and dispersion strengthening of the nanosized phases. (C) 2021 Elsevier B.V. All rights reserved.

Thin-walled copper tube is widely used in the heat-transfer fields, as a main component of various equipment, due to its highly efficient heat conductivity. However, the surface roughness problem (so-called orange peel) after bending deformation is raised as a limitation for its application. In this study, the relationship between microstructural parameters and the surface roughness was investigated by using electron back-scattered diffraction technique and surface mapping microscope test. The results show that, the surface roughness can be influenced both by grain size and texture components of the copper tube. The value of surface roughness is increased with the increasing of grain size at a certain scale. Meanwhile, improving the fraction of Goss texture component can reduce the degree of roughness, due to the Goss oriented-grains were prone to slip during bending deformation.

The texture evolution of copper tube manufactured by floating plug drawing process was investigated by Electron Backscatter Diffraction techniques and Visco-Plastic Self-consistent (VPSC) modelling method. The results obtained from experimentation indicate that the initial textures of copper tube transformed sharply after the first pass of the drawing process, and the final textures in the tube consist of Goss {110} <001> and P {110} <111> components. The VPSC model was established in order to study the texture transformation and the activity of slip systems of the tube during the drawing process. Two types of transformation paths were proposed to explain the mechanism of the texture evolution, which has a good agreement with the VPSC simulation results.

To study the dynamic recrystallization and texture evolution of GH4169 alloy during the cross wedge rolling processing, the microstructure, crystal orientation and texture in the surface and core of the GH4169 alloy with the area reduction of 30 and 50% were analyzed by the metallographic microscope (OM) and electron backscatter diffraction (EBSD) , respectively. The results show that the crystal orientation gradually tends to be random with the occurrence of dynamic recrystallization during the cross wedge rolling process of GH4169 alloy. There are more high-angle grain boundaries in the rolled surface than those in the core. No evident change of the texture intensity in the rolled surface can be observed, while the core texture intensity increases obviously. The textures have rotated after the cross wedge rolling and the previous types of { 001 } <1<(1)over bar>0> { 111 } <1<(1)over bar>0>, {111} <0<(1)over bar>1> change to the types of {001} <0<(1)over bar>0>, {112} <1<(1)over bar>0>, {110} <1<(1)over bar>1> , {110} <1<(1)over bar>2>. The dynamic recrystallization and texture evolution of GH4169 alloy are dominated by the special deformation characteristics of the cross wedge rolling.

The microstructure evolution and dynamic recrystallization mechanism of GH4169 alloy rolled by cross wedge rolling were characterized by metallographic microscope and electron backscatter diffraction (EBSD). The effects of equivalent strain, strain rate and temperature on the dynamic recrystallization of GH4169 alloy during cross wedge rolling were investigated by numerical analysis. The results reveal that the shaping characteristics of cross wedge rolling are the main reasons that induce the homogeneous microstructure and different dynamic recrystallization mechanisms of GH4169 alloy. Larger reduction of area is beneficial to improving the microstructure homogenization. The non-continuous dynamic recrystallization mechanism is the main form on the surface of the rolled piece, while the core is dominated by continuous dynamic recrystallization mechanism.

为了研究铜管材游动芯头拉拔成形过程中组织结构及力学性能变化规律,采用OM和EBSD等试验方法对不同拉拔变形量的TP2管材进行分析.结果表明:经过拉拔变形后,晶粒沿着拉拔方向伸长形成纤维组织,管材显微硬度增加且轴向硬度值较高;经过第三道次拉拔变形量达到75％,晶粒沿轴向长度为80～100μm,宽度为8～10μm;经过拉拔变形,管材内部织构发生转变,随着变形量的提高,由原始轧制态{001}<110>、{111}<110>织构逐渐发生转动,经过三个道次后变为{110}<100>、{110}<111>织构.

目的 研究行星轧制变形程度对TP2铜管材在轧制和联拉时的组织和性能的影响.方法 采用金相显微分析和拉伸实验,研究行星轧制变形程度对TP2铜管铸坯轧拉态以及拉拔态组织及性能的影响规律.结果 经连续铸造的TP2铸坯为柱状晶,且由外向内成长.经行星轧制、联拉后的管材晶粒纤维流线,其晶粒显著拉长,随着轧制变形程度的增加,流线减弱,晶粒更加细化.轧制变形程度为93％与90％的轧管屈服强度、抗拉强度分别降低了22.83％和7.59％,伸长率提升了4.44％,塑性变形能力增加.结论 随着轧制变形程度的增加,联拉管抗拉强度略有提高,而伸长率得到了保持.

通过组织分析、性能测试、表面腐蚀及铜粉检测,论述了铜杆晶粒组织、次表层质量、扭转后表面质量、铜粉量对漆瘤的影响.提出了适用于漆包线用铜杆的控制要求及选材标准,以减少漆瘤,提升产品质量.

The TP2 copper tube was prepared with La microalloying by horizontal continuous casting (HCC). The absorptivity of La and its effects on microstructure, tensile and corrosion properties of HCC TP2 copper tube were studied by means of the inductively coupled plasma optical emission spectrometer (ICP-OES), optical microscope (OM), scanning electron microscope (SEM) and potentiodynamic polarization measurements. The results show that the absorptivity of La in the HCC TP2 copper tube is about 15% under antivacuum conditions due to the good chemical activities of La. The impurity elements in copper tube such as O, S, Pb and Si can be significantly reduced, and the average columnar dendrite spacing of the copper tube can also be reduced from 2.21 mm to 0.93 mm by adding La. The ultimate tensile strength and the elongation with and without La addition are almost unchanged. However, the annual corrosion rate of the HCC TP2 copper tube is reduced from 10.18 mm•a-1 to 9.37 mm•a-1 by the purification effect of trace La.

The deformation and internal defect in the flat-wedge cross-wedge rolling (CWR) of GH4169 superalloy were investigated numerically using a coupled thermo-mechanical finite element analysis (FEA) model. The simulation analysis showed that the temperature distribution in the work piece was non-uniform during the flat-wedge CWR. When the initial temperature of the work piece was relatively low, the work piece temperature increased, a heating effect of the plastic deformation, while relatively high initial work piece temperatures resulted in cooling the work piece, caused by the work piece contact with the tools. It is noted that the increase of tools moving speeds is helpful to reduce the generation of internal defects in the flat-wedge CWR of GH4169 alloy. An important tendency is that both increasing the tools temperature and decreasing friction coefficient all can contribute to avoiding the center defects in the flat-wedge CWR of GH4169 alloy

A sudden columnar-to-equiaxed transition (CET) of cast copper with rare earth (RE) microalloying has been examined. Some solidification parameters of Cu–La alloys were determined by using optical microscopy and differential scanning calorimetry, and simulation of temperature field in copper ingot solidification process. It is noted that the addition of RE microalloying can purify the alloy and make an interaction between equiaxed nucleation and constitutional undercooling, which results in a sudden CET. Furthermore, a new prediction model of the critical alloy composition condition for the CET induced by RE microalloying is established. The critical compositions of a sudden CET of cast copper with La addition is 0.14wt.%, which is in good agreement with the experimental results. It is suggested that increasing the alloy content is very necessary at a high gradient in order to promote the CET. However, the number N0 of effective nucleation sites should also be increased with the decrease of the alloy composition. Meanwhile, it can be found that the columnar region can be expanded with the increase of the temperature gradient. It is obvious that lowering temperature gradient contributes to promote the CET. The prediction model can also be used in the common CET very well.

Cu-La alloys with various additions of La were prepared in a vacuum electric furnace. The effects of La additions on the absorptivity and purification of La in as-cast pure copper were investigated. The results show that the absorptivity of La increases with increasing additions. However, this is as a result of reactions with impurity elements in the copper and further oxidation in the atmosphere. Meanwhile, the addition of La further reduces the contents of impurity elements such as Si, Pb and S, and purifies liquid copper more effectively, which can help to improve the mechanical properties of as-cast pure copper. However, excessive rare earth element additions can lead to decreases in elongation due to the excessive formation of intermetallic compounds. This paper is part of a Themed Issue on Brass Alloys.

According to modified Miedema’s theory, mixing enthalpies (ΔH), excess entropies (S E), excess Gibbs free energy (G E), and component activities (a) of Cu–La binary alloy were estimated using the basic thermodynamic principles and some simple physical parameters of Cu and La, such as electronegativity, atomic volume and electron density. Based on the Cu–La binary alloy phase diagram, the Gibbs free energy of the phase precipitation reactions of Cu6La and Cu5La was deduced. The results showed that the values of ΔH, S E, and G E of Cu–La binary alloy were all negative. Compared to the ideal solution, the activities of the components presented a large negative deviation from Raoult’s law, which indicated that there was a strong interaction between Cu and La. The calculated data are well consistent with the experimental data. The Gibbs free energies of the phase precipitation reactions of Cu6La are lower than those for Cu5La, which means that Cu6La is thermodynamically more stable than Cu5La. Furthermore, the experimental results show that rareearth rich Cu6La phase particles in copper matrix are formed after La microalloying.

The effects of small amount addition of the rare-earth Ce on the microstructure, mechanical properties, and corrosion resistance behavior of cast pure copper were investigated using optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectrometry (EDS), transmission electron microscopy (TEM), tensile testing, and potentiodynamic polarization measurements. It was indicated that Ce addition significantly refined the grain and enhanced the tensile strength of cast pure copper. Copper alloy with 0.12 wt.% Ce addition had the smallest equiaxed grains of 358. ± 23.53 μm and the ultimate tensile strength of 181.7 ± 3.7 MPa. Ce formed spherical second phase particles with copper, which were revealed as Cu6Ce by EDS and TEM results. Solid solution strengthening, fine-grain strengthening, and second-phase precipitation strengthening played important roles in the tensile strength improvement. However, the elongation decreased due to the second phase particles’ inhomogeneous distribution. The corrosion resistance properties of micro-alloyed copper alloys in 0.5 mol/L HCl solution were improved when Ce addition was limited to less than 0.069 wt.% owing to a purification effect and the formation of a compact corrosion product film on the copper matrix. The influencing mechanisms of Ce on the microstructure, mechanical property, and corrosion property were also discussed in detail.