Copper-manganese Alloys Research Articles

Oxidation of copper-manganese alloys under pure oxygen

Oxidation, in oxygen gas at atmospheric pressure, of copper-manganese alloys (Mn content less than 40 at.%) has been investigated between 600 and 850° C. The reaction kinetics, determined by thermogravimetry, follow a parabolic law for alloys having a low manganese content (less than 10 at.% Mn) but are more complex for higher concentrations, particularly in the first stages of the oxidation process. Whereas in the early stages of oxidation the kinetics are controlled by surface reactions which accompany the formation of the different oxide layers, they are later controlled by the diffusion of a mobile species when the parabolic law is followed. In this condition an apparent activation energy may be determined from the rate constants. These energies are of the order of 120–140 kJ mol−1, comparable with that for oxidation of pure copper (134 kj mol−1), indicating a similar oxidation mechanism.

THE MAGNETISM OF METALLIC MANGANESE ALLOYS

The magnetic excitations in antiferromagnetic manganese-copper and manganeseiron alloys are characterized by high spin-wave velocities, an energy gap at long wavelengths and wavelength dependent damping. There are strong elastic constant anomalies above TN as well as magnetoelastic distortions below TN. The theoretical explanation of these effects is reviewed.

Excitation of Lattice Reorientations in "Tweedy" Copper-Manganese Alloys

Excitation of Lattice Reorientations in "Tweedy" Copper-Manganese Alloys

Short-range order in copper-manganese alloy single crystals

Short-range order in copper-manganese alloy single crystals

Oxidation studies of copper-manganese alloys — A basis for model catalyst preparation

The oxidation of various compositions of Cu-Mn polycrystalline alloys and a Cu-Mn(7.5%) single crystalline alloy has been studied by X-ray photoelectron spectroscopy (XPS) over the temperature range from room temperature to 500°C at oxygen pressures varying from 10 -5 Torr to 1 atm. It has been established that the complex behavior of the oxidation and the ultimate nature of the oxide layers are controlled by temperature, oxygen pressure and alloy composition with dominance at low temperatures and pressures by relative free energies of oxide formation. The composition and structure of the oxide films have been examined in detail by XPS.

Use of damping materials for increasing the quality and service properties of parts

Type 04Kh11Yu chromium-aluminum steels are promising high-damping materials. They contain readily available alloy elements and are more corrosion- and scale-resistant than such high-damping alloys as magnesium and manganese-copper alloys and cast irons. In addition, they are more easily melted and hot worked by pressure than magnesium and manganese-copper alloys. Heat treatment of chromium-aluminum steels for high damping is simple.

Cyclic shape memory in copper-manganese alloys realized with alternating stresses

The phenomenon of shape memory in materials is used extensively in order to study physicomechanical properties of materials. In this respect there is considerable interest in materials with shape memory properties used for the operating part of thermal machines under cyclic operating conditions [i-4]. In order to obtain useful operations, it is necessary to create a certain thermodynamic cycle.

Spin density wave magnetism in copper—manganese alloys

The incommensurate magnetization waves (IMW) occuring at the wave vector Q = (1, 0.5 − δ, 0) 2π a and equivalent positions in reciprocal space in Cu 1− x Mn x have been studied as a function of temperature, wavevector, frequency and composition, using high-resolution, unpolarized neutron scattering techniques. We find that the elastic component of the scattering cross section at these incommensurate wavevectors approaches zero in the vicinity of the “spin glass” freezing temperature, T f , closely resembling that expected for an order parameter on approach to the critical point. We suggest that the interaction between Mn atoms is long-range and intimately connected to a spin density wave instability.

Investigation of the properties of PMFOTsr6-4-0.03, PMFS6-0.15, and P29-76 silver-free brazing metals at cryogenic temperatures

The acute shortage of silver has made necessary the development and sue of silverfree brazing metals. As replacements for silver brazing metals in brazing joints operating at normal temperatures, brazing metals developed on the basis of copper-phosphorus and copper-manganese alloys are recommended. In this work, an investigation was made of the mechanical and production properties of PMFOTsr6-4-0.03, PMFS6-0.15 and P29-76 brazing metals for the purpose of determining the possibility of their use in the production of cryogenic equipment. As the test data indicate, with the use of copper-phosphorus brazing metals it is impossible to obtain cold-resistant brazed joints of copper and brass. The joints of steels brazed with the copper-manganese brazing metal do not possess plasticity either at 293/sup 0/K or at 77/sup 0/K. The joints of copper brazed with P29-76 brazing metal have quite high characteristics of plasticity, which do not change with a reduction in temperature to 77/sup 0/K, indicating their cold resistance at cryogenic temperatures. However, this metal wets the surface of copper poorly and flows into the gap only after repeated addition of flux and strong heating of the sample. For solution of the problem, it is desirable to develop a highly active flux for gasmore » torch brazing with copper-manganese brazing metals and to study the possibility of the use in cryogenic technology of brazing metals of the copper-manganese system alloyed with nickel.« less

Examination of the effect of static tensile stresses on the damping capacity of manganese-copper alloys with allowance made for temperature

According to the literature data [3], the degree of energy scattering in the manganese-copper alloys is greatly reduced during heating, especially at temperatures to 100~ The nature of the effect of static tensile loading on the damping capacity may vary considerably and depends on the degree of tetragonality of the crystal lattice, the density of elastic twins, and also on the ratio of static and dynamic stresses [4-6].

Metallographic method for manganese-copper alloys

It is demonstrated that electrolytic polishing in an orthophosphoric acid-glycerol-ethyl alcohol solution followed by etching in diluted electrolyte produces a satisfactory surface for examination of the structure of manganese-copper alloys using polarized light illumination.

High-temperature oxidation of copper-manganese alloys

The oxidation behavior of copper-manganese alloys (2–35 wt. % Mn) in pure oxygen at 760 Torr was investigated at 100° intervals between 550 and 850°C. Gravimetric measurements of the oxidation kinetics have been combined with microstructural studies of the reacted samples in order to evaluate the reaction mechanisms. The scales formed on Cu-2Mn, Cu-5Mn, Cu-10Mn are always composed of three different layers; in any case manganese is present only in the inner layer. The scales formed on Cu-20Mn and Cu-35Mn are composed of two layers, both containing manganese, with a more Cu-rich outer layer. In all the samples internal oxidation in combination with external scale formation is observed.

An investigation of precipitation and strengthening in age-hardening copper-manganese alloys

The age-hardening characteristics of CuMn alloys containing 38–58% Mn have been investigated. Ageing was found to result in the formation of a single, spherical, coherent transition phase, which retained its coherency to long ageing times and also after plastic deformation. The growth rate of the transition phase followed the t 1 3 growth law for spherical precipitates. Single peaked strength increases accompanied ageing in all alloys. The variation in strength throughout ageing has been identified with dislocation shearing of deformable particles and this has been used to account for the low work-hardening rates in these alloys. At long ageing times, the equilibrium α-Mn phase precipitated at grain boundaries and was accompanied by the formation of a broad, precipitate-free zone, resulting in considerable embrittlement of the alloys.

Effect of certain chemical elements and heat treatment on damping capacity of manganese-copper alloys

Effect of certain chemical elements and heat treatment on damping capacity of manganese-copper alloys

Magnetic and atomic correlations in dilute copper-manganese alloys

Magnetic correlations in paramagnetic CuMn alloys containing up to 10 at.% Mn measured using neutron polarization analysis are compared with the predictions of the RKKY interaction and found to agree with the accuracy of the measurements. This implies a ferromagnetic first neighbour interaction. The susceptibility decreases and the atomic short-range order increases in a 1 at.% alloy on annealing at 100 degrees C. The low temperature magnetic order is described more closely by the cluster model of Beck (1972) than by the analysis of Klein and Briut (1963).

Relaxation and magnetic clusters in mictomagnetic copper-manganese alloys

Quantitative data were obtained on the average giant moment and the concentration of the magnetic clusters in CuMn alloys. For aged Cu 75Mn 25 the magnitude of the giant moment is consistent with the size of the small, atomically-ordered regions, determined by Sato et al. by means of nuclear diffuse neutron scattering. Contrary to an early model, the results do not indicate that the concentration of giant moments is measurably affected either by cooling in a magnetic field or by isothermally increasing the applied magnetic field. The relaxation of the giant moments in the applied field is responsible for most of the alternating low field susceptibility at its peak and this relaxation also gives rise to the “quasi-viscous” time-dependence of the steady field magnetization in a certain temperature range below the peak. At very low temperatures, where the relaxation effects are frozen out, it is the “quasi-elastic” response of the giant moments that is responsible for the exceedingly high steady field susceptibility.

Resistance of thin films of copper and copper alloys deposited at temperatures less than 10 K

An apparatus has been developed for the deposition of evaporated films at less than 10 K and the subsequent measurement of resistance of the fihns between 1.5 and 300 K. In this paper results are given for the annealing on the films with emphasis on the sharp transition temperature at which irreversible annealing commences. This is 15 +_ 1 K for Cu fihns and 31 +_ 2 K for alloys of manganese in copper.

Composition of Oxide formed on Copper and Copper–Manganese Alloys (5–40% Mn) in Oxygen at 150°–600°c

The proportions of CuO and Cu2O in films formed on copper and copper-manganese alloys in oxygen at temperatures of 150–400°c (600°c for higher Mn alloys) were estimated by coulometric reduction. Only Cu2O was observed at 150°c. The proportion of CuO increased as the temperature was raised, reaching 82% for copper at 300°c and somewhat lower values for the alloys containing Mn. At temperatures of 350–400°c, the proportion of CuO declined. The oxide remained adherent above 400°c only for alloys with 20% and 40% Mn. From 400° to 600°c the proportion of CuO increased for the 20% alloy but neither CuO nor Cu2O was found on the 40% alloy.

Interaction effects in copper-manganese alloys at low temperatures

The results of resistivity measurements on CuMn alloys from 10 ppm to 1% between 30 mK and 4K are presented. They show the important role played by interactions between the manganese impurities even at extremely low concentrations. An anomalous variation of the resistivity at low values of (T/c) has been observed. Several possible explanations for this behaviour are suggested.

Effect of Composition on the Internal Friction and Young's Modulus in γ Phase Mn-Cu Alloys

A detailed investigation has been made regarding the variation in internal friction and Young's modulus with temperature in manganese–copper alloys containing 11.74–26.08 wt.-% Cu. It was confirmed that the transformation temperature for the fct → fcc reverse martensitic transformation in quenched specimens is reduced from 129 to – 76° C (402 to 197 K) with increase in Cu content from 11.74 to 26.08 wt.- %. This is in good agreement with the results of previous workers. The internal friction was found to exhibit a ‘main peak’ and a ‘sub-peak’. The former appeared at ∼ 3°C (276 K) in all specimens containing < 21 wt.-% Cu, while the latter was observed at the temperature of the reverse martensitic transformation (Tt ) in each specimen. It is concluded from detailed analysis that the main peak is due to a relaxation process associated with the movement of the {10l}-twin boundaries in the fct phase, the activation energy and the frequency factor being, respectively, ∼ 5.15 × 104 J“g atom and 2.4 × 1013 S−1 for a sample containing 11.74 wt.-% Cu. The nature of the sub-peak, however, is not well understood. It is tentatively suggested that it may be closely connected with the movement of interfaces separating the fcc phase from the fct phase. The anomaly in Young's modulus observed at Tt can be satisfactorily explained in terms of a strain-dependent exchange model and the fairly close connection between the martensitic transformat ion and the magnetic transition in this alloy is pointed out.