The thermodynamic activities of copper and iron in the system copper-iron-platinum at 1300°C

The vapor pressure of pure liquid copper and the partial pressures of copper exerted by six alloys in the system Cu−Fe, 12 alloys in the system Cu−Pt, and 44 alloys in the system Cu−Fe−Pt in the temperature range 1240°C to 1360°C have been measured by the Knudsen effusion technique, and the thermodynamic properties of the systems at 1300°C have been calculated from the vapor pressures. The system Cu−Fe shows large positive deviations from Raoultian ideality, and the system Cu−Pt shows large negative deviations. The activities of Fe in solid solutions in the system Cu−Fe−Pt at 1300°C have been calculated by Gibbs-Duhem integration of the activities of Cu. This paper is based on a presentation made in the T.B. King Memorial Symposium on “Physical Chemistry in Metals Processing” presented at the Annual Meeting of The Metallurgical Society, Denver, CO, February, 1987, under the auspices of the Physical Chemistry Committee and the PTD/ISS.     

Electrical Resistivity and Short-Range Order in Copper Melts with Yttrium

The electrical resistivity of liquid Cu – Y alloys in the region of compositions 0-70 at.% yttrium at temperatures in the range 1200-1600 K is measured by means of a four-probe method. Intensive growth in the electrical resistivity of the melts is found with increasing yttrium concentration, with only weak temperature dependence of electrical resistivity. Percolation theory is applied to calculate the electrical conductivity of Cu – Y melts, taking into account thermodynamic data for ordered melts in an approximation to the associated solution model.     

Thermophysical Properties of Liquid Aluminum

Ohmic pulse-heating with sub-microsecond time resolution is used to obtain thermophysical properties for aluminum in the liquid phase. Measurement of current through the sample, voltage drop across the sample, surface radiation, and volume expansion allow the calculation of specific heat capacity and the temperature dependencies of electrical resistivity, enthalpy, and density of the sample at melting and in the liquid phase. Thermal conductivity and thermal diffusivity as a function of temperature are estimated from resistivity data using the Wiedemann–Franz law. Data for liquid aluminum obtained by pulse-heating are quite rare because of the low melting temperature of aluminum with 933.47 K (660.32 °C), as the fast operating pyrometers used for the pulse-heating technique with rise times of about 100 ns generally might not be able to resolve the melting plateau of aluminum because they are not sensitive enough for such low temperature ranges. To overcome this obstacle, we constructed a new, fast pyrometer sensitive in this temperature region. Electromagnetic levitation, as the second experimental approach used, delivers data for surface tension (this quantity is not available by means of the pulse-heating technique) and for density of aluminum as a function of temperature. Data obtained will be extensively compared to existing literature data.

     

铜锡合金激光选区熔化非平衡凝固组织与性能

对具有重要工程应用价值的Cu?5%Sn合金进行激光选区熔化（SLM）成形,在激光功率160 W、扫描速度300 mm·s?1、扫描间距0.07 mm条件下,合金样品相对密度可达99.2%,熔池层与层堆积密实,表面质量良好。研究发现所获合金具有非平衡凝固组织特征,其中以α-Cu(Sn)固溶体相为主,且涉及具有超结构的γ相、δ相。显微形貌主要由柱状晶与富锡网状组织构成,伴随有不同尺度界面Sn元素偏析及晶界、晶内纳米尺寸超结构合金相颗粒析出。所获合金的力学性能与同成分铸态合金或较低Sn含量SLM合金相比得到显著强化,表面硬度可达HV 133.83,屈服强度326 MPa,抗拉强度387 MPa及断裂总延伸率22.7%。      

Thermophysical Properties of a Fe‐Cr‐Mo Alloy in the Solid and Liquid Phase

Results of a thermophysical characterization of a Fe‐Cr‐Mo alloy in the solid and liquid phases are reported. Methods applied include calorimetry, dilatometry; the laser flash technique for thermal diffusivity measurement and ultrasound pulse echo for the measurement of the room temperature sound velocities and elastic constants. Density in the liquid phase and surface tension were measured by optical dilatometry and by the oscillating drop method on electromagnetic levitated specimen. In addition, surface tension and viscosity were measured by the oscillating drop method on board parabolic flights under reduced gravity conditions. The methods applied and results obtained are presented. This work represents a collaborative effort, including round robin measurements in different laboratories for a characterization of the basic thermophysical properties needed for process simulation.     

细晶W-Cu合金的高温拉伸力学行为与组织演变

研究了平均晶粒度在0.5μm以下细晶W-40Cu和W-50Cu合金在200~800℃范围内的高温拉伸力学行为,并结合SEM断口形貌分析了材料在高温状态下的断裂形式及其组织变化规律。结果表明:W-Cu合金拉伸强度随温度升高而迅速降低,其延伸率在室温至400℃温度区间时变化不大;当温度大于400℃时,合金延伸率迅速上升。拉伸断口特征表明:在室温条件下,细晶W-Cu合金的断裂主要包括W晶粒的沿晶断裂与Cu相的延性撕裂;温度在400℃时,Cu相开始软化,但合金材料受铜的"中温脆性"影响而使得材料的断裂延伸率变化不大;当温度达到800℃时,材料的断裂方式主要受Cu相的影响而表现出很好的延性断裂。     

Microstructures,mechanical properties,and electrical resistivity of rapidly quenched Fe-Cr-Al alloys

By the rapid quenching technique, ductile supersaturated ferrite solid solution with high hardness and strength as well as unusual electrical properties has been found in Fe-Cr-Al ternary system. This formation range is limited to less than about 35 at. pct Cr and 23 at. pct Al. The ferrite phase has fine grains of about 10 μm in diameter. Their hardness, yield strength, and tensile fracture strength increase with increase in the amounts of chromium and aluminum, and the highest values reach about 290 DPN, 720 MPa, and 740 MPa. These alloys are so ductile that no cracks are observed even after closely contacted bending test. The good strength and ductility remain almost unchanged on tempering for one hour until heated to about 923 K where a large amount of Cr₂Al compound begins to precipitate preferentially along the grain boundaries of the ferrite phase. The room-temperature resistivity increases with increasing chromium and aluminum contents and reaches as high as 1.86 μ Ώ m for Fe₅₀Cr₃₀Al₂₀ alloy. Also, the temperature coefficient of resistivity in the temperature range between room temperature and 773 K decreases with increasing chromium and aluminum contents and becomes zero in the vicinity of 20 to 30 at. pct Cr and 15 at. pct Al. Thus, the present alloys may be attractive as fine gauge high-resistance and/or standard-resistance wires and plates because of the unusual electrical properties combined with high strength and good ductility. formerly with the Research Staff of Tohoku University formerly Graduate Student of Tohoku University,     

Preparation and Mechanical Properties of Misch Metal Based Bulk Metallic Glasses

Bulk metallic glasses(BMGs)have been devel-oped in many alloy systems during past decade.Among these systems,rare-earth(RE)metal-basedBMGs are ones of those found earliest and with betterglass forming ability(GFA).For example,La-basedBMGs were the first a…     

强变冷形单晶铜线退火过程组织性能演变研究

经强冷变形后的单晶铜线会产生明显的亚结构。在退火过程中该亚结构将发生转变．以中拉单晶铜线为对象,通过金相、力学性能测试法、电阻测试等手段研究了经强冷变形后的单晶铜线在不同退火工艺制度下的组织性能变化和再结晶过程．研究结果表明：加工态单晶铜线材的再结晶温度开始在250℃左右,比相同冷变形率下的SCR连铸纯铜杆的再结晶温度高约50℃．强冷变形单晶铜线再结晶形核的孕育期随温度升高而缩短．500。C时的孕育期不足2min．单晶铜在退火的回复阶段导电性能得到改善,但温度较高发生再结晶时,由于晶界数量的不断增加,有抑制电阻率减小的作用．强冷变形后的单晶铜线要想恢复足够的塑性,则难以避免成为多晶,如果既要恢复单晶铜线的塑性和导电性,又要维持单晶的组织形态,进行高温超短时间退火将有助于解决这一问题．     

Effects of squeeze casting on the properties of Zn-Bi monotectic alloy

In composite production, the shortest route is via an in situ composite in which a melt dissociates simultaneously into two rather different solid phases. The monotectic alloys can be included in this group. The present work was aimed at extending our recent squeeze casting experience on the Zn-Bi monotectic alloy in order to increase its cast quality and mechanical properties. A squeeze casting unit was built, and its die and punch were machined. The molten monotectic alloy was squeezed in this unit under pressures up to 120 MPa in its freezing range until it solidified completely. It was found that an increase in squeeze casting pressure provided increases in density, tensile strength, and Vickers hardness, which resulted in decreases in chip length and electrical resistivity. Before the squeeze casting practice, the freezing characteristics of this monotectic were estimated using basic solidification principles.     

Structure and properties of Cu-Cr alloys subjected to shear under pressure and subsequent heating

The effects of the chromium content (0.75, 9.85, 27%) in Cu-Cr alloys, their initial state, and the heating temperature on their thermal stability after severe plastic deformation are studied by microhardness and electrical resistivity measurements and metallography. The microhardness and electrical resistivity of Cu-Cr alloys are determined as functions of the heating temperature in the range 50–600°C, and microhardness distributions over the diameter of samples differing in the chromium content are plotted. The difference in the strengthening and softening of low- and high-alloy copper-chromium alloys subjected to high-pressure torsion is shown to be related to the initial structure of the material.     

Al-rich portion of the Al-Hf phase diagram

Electrical resistivity measurements, differential thermal analysis, optical microscopy, and the deposition of hafnium compound particles from a melt are used to study the Al-rich portion of the Al-Hf phase diagram. Prominence is given to the hafnium solubility in solid and liquid aluminum. The studies show a peritectic character of the invariant reaction during the solidification of alloys with sufficiently high hafnium contents and a slight difference between the peritectic and melting temperatures of pure aluminum. The hafnium solubility in solid and liquid aluminum is shown to increase with the temperature. The hafnium solubility in solid aluminum at the peritectic temperature (maximum solubility) is 1.00 wt % (0.153 at %); the hafnium solubility in liquid aluminum at this temperature is 0.43 wt % (0.065 at %).     

Thermodynamic study of liquid Cu-Mg alloys by vapor pressure measurements

Thermodynamic properties of liquid Cu-Mg alloys have been determined by magnesium vapor pressure measurements over pure liquid magnesium and liquid Cu-Mg alloys, in the composition range of 11 to 90 mole pct Mg between 845 and 1345 K, employing the transpiration technique. Based on the quadratic formalism suggested by Turkdogen and Darken for binary systems, analytical expressions have been derived representing integral and partial molar thermodynamic properties as functions of composition for the two terminal regions of suN Mg = 0 to 0.33 and 0.6 to 1.0. From the measured activity values of magnesium and copper, in the liquid alloys in equilibrium with solid intermetallic compounds, standard free energies of formation of Cu₂Mg(s) and CuMg₂(s) relative to pure solid components have been calculated and expressed as functions of temperature. Extractive Metallurgy Section, Metallurgy Division     

Diffusional breakdown of nickel protective coatings on copper substrate in silver-copper eutectic melts

Diffusion couples with electrolessly plated nickel diffusion barriers between copper substrates and silver-copper eutectic alloys were tested at 800 °C and 850 °C, respectively. Growth of (Cu, Ni, Ag) ternary solid solution into the melt was observed at both temperatures. The growth pattern changed from cellular to dendritic as the temperature was increased from 800 °C to 850 °C. The nonplanar growth morphology can be explained in terms of constitutional supercooling in the melt. Kinetics of (Cu, Ni, Ag) solid solution growth were found to be controlled by interdiffusion at the interface of the nickel barrier and the growing solid-state phase. Local breakdown of the nickel diffusion barrier started once the (Cu, Ni, Ag) solid solution reached the copper substrate. Silver diffused from the silver-copper melt, through the ternary solid solution, dissolving copper and forming silver-copper liquid along copper grain boundaries. Ultimately, the nickel barrier was totally converted to the ternary solid solution, broke up, and floated into the liquid. Dissolution of the copper substrate occurred subsequently. A thin layer of chromium undercoating proved to be very effective in extending the protection time of the nickel diffusion barrier, due to the extremely low solubility of both copper and silver in chromium at these test temperatures.     

Activity and diffusivity measurements of copper in γ and δ Fe by equilibration between solid Fe and liquid Ag

The activities of Cu in solid Fe for 1323 <=T <= 1773 K have been determined by equilibrating the surface of initially pure Fe plates with liquid Ag-Cu alloys and by using the literature values of the Cu activity in Ag-Cu alloys. The equilibrations have been confirmed by the agreement of surface compositions between an initially pure Fe plate and an Fe-Cu alloy plate having more content of Cu than the surface concentration. The equilibrated Fe plates were essentially binary Fe-Cu alloys, because no Ag was detected by an electron probe analyzer in the Fe plates. Interdiffusivities in solid Fe-Cu alloys for the same temperature range have also been determined from penetration profiles of Cu in the plates. The ternary phase diagram for the Ag-Cu-Fe system at 1480 K has been determined from solubility measurements of Fe in liquid Ag-Cu alloys. M. Tanaka, formerly at Tokyo Institute of Technology, is now with Clinap Industries, Tokyo, Japan.     

Determination of the thermophysical properties of titanium alloys from liquid bath profiles

An experimental–theoretical technique is proposed to determine the thermophysical properties of titanium alloys in the liquid phase. This technique is based on analyzing the liquid bath profiles in fully solidified ingots after vacuum arc remelting (VAR). The experimental part of the technique makes it possible to easily estimate liquid bath contours without any markers, such as radioactive isotopes. The theoretical part is based on solving the inverse heat conduction problem for a solidifying ingot. The developed technique is used to determine some thermophysical parameters of the liquid bath and boundary conditions for VAR of titanium alloys Ti–6Al–4V, Ti–5Cr, and Ti–3Fe, since it is extremely difficult to measure them directly.     

连续变温金属固-液电阻率测试装置及应用

概述了液态金属电阻的测试方法，利用直流恒流四电极法测量原理建立了固-液金属电阻率连续变温测试装置，并利用该装置对合金Ph61.9Sn38.1及固体非晶Zr57Nb5Cu15.4Ni12.6A.10的电阻率进行了连续变温测量，验证了该装置测试的可靠性。     

不同冷速凝固的Mg-9Gd-0.8Al合金固溶行为及组织性能

为了探究Al元素在不同冷却速度下对Mg-9Gd合金组织细化效果及其对后续固溶处理的影响,利用铁模和铜模重力铸造制备了铸态Mg-9Gd-0.8Al合金,之后进行10～50 h的固溶处理。采用OM、SEM、TEM、EDS及XRD等方法研究了冷却速度对Mg-9Gd-0.8Al合金凝固和固溶行为及组织力学性能的影响。结果表明,铁模和铜模制备的铸态Mg-9Gd-0.8Al合金组织均由α-Mg基体、花瓣状(Mg, Al)₃Gd相、细条状Mg₅Gd相和方块状Al₂Gd相组成。铜模相比于铁模冷却速度加快,制备的合金基体晶粒和第二相显著细化,第二相体积分数总量增长幅度达56.1%。2种模具制备的合金固溶10 h后,Mg₅Gd相溶解、(Mg, Al)₃Gd相部分溶解、高熔点Al₂Gd相无变化,晶粒内析出层片状(Mg, Al)₂Gd新相,第二相总量趋于相等。固溶50 h后,(Mg, Al)₂Gd层片相回溶,残余(Mg, Al)     

不同冷速凝固的Mg-9Gd-0.8Al合金固溶行为及组织性能

为了探究Al元素在不同冷却速度下对Mg-9Gd合金组织细化效果及其对后续固溶处理的影响,利用铁模和铜模重力铸造制备了铸态Mg-9Gd-0.8Al合金,之后进行10~50 h的固溶处理。采用OM、SEM、TEM、EDS及XRD等方法研究了冷却速度对Mg-9Gd-0.8Al合金凝固和固溶行为及组织力学性能的影响。结果表明,铁模和铜模制备的铸态Mg-9Gd-0.8Al合金组织均由α-Mg基体、花瓣状(Mg, Al)₃Gd相、细条状Mg₅Gd相和方块状Al₂Gd相组成。铜模相比于铁模冷却速度加快,制备的合金基体晶粒和第二相显著细化,第二相体积分数总量增长幅度达56.1%。2种模具制备的合金固溶10 h后,Mg₅Gd相溶解、(Mg, Al)₃Gd相部分溶解、高熔点Al₂Gd相无变化,晶粒内析出层片状(Mg, Al)₂Gd新相,第二相总量趋于相等。固溶50 h后,(Mg, Al)₂Gd层片相回溶,残余(Mg, Al)₃Gd相发生熔断呈颗粒状,铜模制备的合金第二相颗粒比铁模的更细小。细晶强化和第二相强化使铜模制备的铸态合金性能较铁模制备的合金性能大幅提高,固溶10 h后合金屈服强度提升,伸长率基本不变。固溶处理50 h后,固溶强化、细晶强化和细小颗粒的第二相强化使铜模制备的固溶50 h态合金获得最优性能,屈服强度、抗拉强度和伸长率分别为141 MPa、234 MPa和22.4%。