Phase Brass Research Articles

Thermally and stress induced changes in three phase structure of Cu–Zn–Al–Fe shape memory alloy

In order to explain the stabilised shape memory behaviour observed during the thermal and mechanical cycling of a Cu–14·86Zn–5·81Al–0·5Fe (wt-%) alloy, X-ray diffraction and optical microscopy studies have been performed. The former have shown that the previously reported reorientation of the α brass phase crystallites from α(111) to α(200), observed during the heating up to 500°C, also occurs during a complete heating–cooling cycle up to 325°C. Optical microscopy studies confirm the increasing tendency for α phase preferred formation when the temperature is increased from 325 to 500°C. This texturing effect that occurs during thermal cycling is accompanied by an increase in the amount of α phase with a reduction in the amount of β2 austenite. Finally, a tensile completely recoverable pseudoelastic strain of almost 0·6%, determined during a loading–unloading cycle applied to a heat treated specimen that contained no austenite, has been ascribed to the reversible formation of a specific martensite variant.

A CsCl-type phase in electrodeposited AlMn alloys

Since the work of Goedecke and Koester it has been known that the central part of the Al-Mn phase diagram is occupied at room temperature by the [gamma][sub 2] phase, while at high temperature two other phases, [gamma] and [gamma][sub 1], have been reported in the same compositional range. A more recent study has confirmed the existence of these phases. The low-temperature phase has a rhombohedrally distorted [gamma]-brass lattice of the Al[sub 8]Cr[sub 5]-type. The structures of the high-temperature phases have not been determined since they could not be retained in alloys quenched to room temperature due to their high transformation rates. Only recently, the structure of the high-temperature [gamma]-phase was studied in-situ by Ellner using x-ray diffraction. According to this study, [gamma] has a bcc structure (W-type) with a lattice parameter of 0.3063 nm. The structure of the second high-temperature [gamma]1 phase has not been determined directly due to technical problems associated with its higher formation temperature; however, it has been suggested to be of the cubic [gamma]-brass type. The previous study of electrodeposited Al-Mn alloys with compositions ranging up to 50 atomic pct Mn revealed a phase exhibiting an x-ray diffraction pattern which was consistent with a CsCl-typemore » structure with a lattice parameter of 0.299 nm. The compositions of the alloys containing this phase ranged from 36 to 43 atomic pct Mn. At lower Mn concentrations, the electrodeposits contained the cubic [gamma]-brass phase described earlier while at higher Mn concentrations, metastable [tau] (CuAu-type) was observed. In this paper the authors confirm the presence of a CsCl-type phase in electrodeposited Al-Mn alloys and associate it with the [gamma]-phase reported by Ellner.« less

Striped-type superstructure in gamma -brass alloys.

The striped-type superstructure in the \ensuremath{\gamma}-brass phase has been investigated both experimentally and theoretically. Electron microscopy observation shows that, in addition to the existence of the striped pattern of the striped-type superstructure, the so-called jellyfish pattern consists of three inversion domains belonging to one of two types. The analysis of the electron-diffraction pattern further leads to an important conclusion that the striped-type superstructure can be interpreted as a structure of the normal \ensuremath{\gamma}-brass type modulated by two incommensurate waves. On the basis of the experimental results, the electronic origin and the discommensurate structure of the striped-type superstructure are discussed. First, the relation between the Fermi surface and the repeated Brillouin zone indicates that the two incommensurate waves have wave vectors determined as a spanning vector of the flat portion of the Fermi surface. Secondly, the Ginzburg-Landau-type model, whose order parameter is the charge density due to the charge density waves, is proposed, and reproduces the experimentally obtained change in the period of the striped-type superstructure. It is also shown that there is a phase slip of 2\ensuremath{\pi}/3 across the discommensuration. These features derived based on the model are entirely consistent with those observed experimentally. Accordingly, it is concluded that the striped-type superstructure in the \ensuremath{\gamma}-brass phase can be interpreted as the charge-density-wave state in the three-dimensional system.

An X-ray and neutron powder diffraction study of ternary gamma brass phases

An X-ray and neutron powder diffraction study of ternary gamma brass phases

Investigation of decalibrated Nicrosil versus Nisil thermocouples: Quantitative sims analysis using indexed sensitivity factors and oxygen flooding☆

X-ray photoelectron spectroscopy has been used to study the oxidation of polycrystalline α(75%Cu/25%Zn) and β(53%Cu/47%Zn) brass. The process was conducted in pure oxygen (10-7 ⩽ PO2 ⩽10-3 Torr) at temperatures between 298 and 433 K. By a careful examination of copper, zinc and oxygen photoelectron and Auger peaks, the differences in growth properties of the oxide layers on the two phases of brass can be deduced. The increase of copper concentration at the surface, for α brass, after high oxygen expossure(for oxygen pressure ⩾10-4 Torr) can be understood by considering the role of oxygen pressure on the growth rate of p-type semiconductor oxide, and the discontinuous character of the oxide layer.

Surface oxidation of polycrystalline α(75%Cu/25%Zn) and β(53%Cu/47%Zn) brass as studied by XPS: Influence of oxygen pressure

X-ray photoelectron spectroscopy has been used to study the oxidation of polycrystalline α(75%Cu/25%Zn) and β(53%Cu/47%Zn) brass. The process was conducted in pure oxygen (10 -7 ⩽ P O2 ⩽10 -3 Torr) at temperatures between 298 and 433 K. By a careful examination of copper, zinc and oxygen photoelectron and Auger peaks, the differences in growth properties of the oxide layers on the two phases of brass can be deduced. The increase of copper concentration at the surface, for α brass, after high oxygen expossure(for oxygen pressure ⩾10 -4 Torr) can be understood by considering the role of oxygen pressure on the growth rate of p-type semiconductor oxide, and the discontinuous character of the oxide layer.

鉛入黄銅中の鉛粒子の析出と粗大化

The machinability of leaded brass is well known to be affected by the microstructural properties of its matrix and microconstituents, particularly by the size and distribution of lead particles, and of course, by variation in machining conditions. The behavior of precipitation and coarsening of Pb particles during solidification and subsequent annealing of α- and β-single phase pure leaded brass was initially assessed by conventional metallographic methods. The size distribution was treated by a new statistical method. The results were later extended to α+β phase commercial leaded α+β brasses.The size and distribution of Pb particles were quite different in the two types of brasses. In as-cast conditions, Pb particles in α-brass were much coarser and precipitated mainly on grain boundaries, while the distribution of Pb particles in β phase brass was relatively homogeneous and its size was much smaller.The diffusion path and preferred nucleation sites of Pb atoms such as dislocations, sub-boundaries and grain boundaries were needed to the coarsening of Pb particles.The solid solubility of Pb was likely to be larger in β-phase than in α-phase, and therefore, the distribution of Pb particles in β-phase was more homogeneous than in α-phase.It was concluded that the size and distribution of Pb particles in commercial leaded brass are determined through the change in the grain structure of α and β phases.

Substrate Effects on Zinc Deposition from Zincate Solutions: I . Deposition on Cu, Au, Cd and Zn

The deposition of zinc on Cu, Au, and Cd from alkaline zincate solutions has been investigated using cyclic voltammetry, potential pulse methods, x‐ray diffraction, and scanning electron microscopy. Deposits on Zn were examined by scanning electron microscopy and x‐ray diffraction. In the case of Au and Cu approximately a monolayer of zinc is formed in the underpotential deposition region prior to bulk deposition. The respective underpotential shifts of Au and Cu are 0.45 and 0.22V and are in good agreement with the difference in work function between zinc and the substrate. Electrodeposited zinc forms an undetermined surface brass phase on Cu and two alloys (and ) with Au. The deposits on all substrates are oriented preferentially parallel to the basal plane.

Evaluation of Corrosion Rate of Copper Alloys by Means of Polarization Measurement

Abstract The polarization resistance measurement was applied for determination of the corrosion rates of 60–40 forged brass and bronze casting in flowing fresh water. The results at three different flow rates (0.1, 1.5, and 3.0 m/s) were compared with the weight loss and dezincification depth obtained after exposure of 180 days. Good agreement was found between the average corrosion current density and the weight loss data. Furthermore, the average depth of dezincification can be predicted from the average corrosion current density under the assumption that dezincification progresses with preferential dissolution of beta brass phase and all beta phases act as the anode while all alpha phases act as the cathode. The effect of flow rate on the corrosion rate can be well described with the mass transfer treatment.

The oxidation of the α and β phases of brass studied by XPS and nuclear reaction spectroscopy

Abstract The oxidation of the α and β phases of brass is studied between 293 and 673 K by means of prompt nuclear reactions, resonant alpha backscattering, and X-ray photoelectron spectroscopy. The oxide layer thickness is obtained from the nuclear methods whereas XPS provides the surface composition and a depth profile of the first few atomic layers. The Zn and Cu oxides are distributed inhomogeneously, and a dependence on phase and sample treatment is observed. In particular, there is an inversion of the oxidation rate between the α and β phase about 523 K. A simple model for the oxide growth mechanism is given.

The oxidation of the α and β phases of brass studied by XPS and nuclear reaction spectroscopy

The oxidation of the α and β phases of brass studied by XPS and nuclear reaction spectroscopy

Stresses, displacements and energy calculations for interfacial dislocations in anisotropic two-phase media

The problem of finding the elastic stress and displacement field around a straight dislocation at the interface separating two media with the most general anisotropic properties, is reduced, similarly to a treatment by Barnett and Lothe (1974), to the inversion of twelve linear equations with twelve unknowns, using the classical formulations of anisotropic elasticity. The opportunity of including constant terms in the analytical form of the displacements is discussed as well as the presence of a resulting couple on the dislocation. The line energy and dilatation field are deduced. Two examples concerning Al/CuAl 2 and α/β brass phase boundary dislocations are treated numerically with help of a FORTRAN computer program. Noticeable effects of both inhomogeneity and anisotropy are revealed. Results for the displacements, stresses and energies are presented.

The use of prompt nuclear reactions and resonant alpha scattering in the study of α and β brass oxidation

The prompt nuclear reaction 16O(d,p 1) 17O and the resonant alpha backscattering 16O(α,α) 16O spectroscopies are used for the measurement of the oxide layer thickness on brass; these methods are subjected to a critical comparison. The study of α and β phase brass oxidation between 293 and 673 K shows clearly the phase and sample treatments dependence. An inversion of the oxidation reactivity between the α and β phase is observed at about 523 K.

Contribution to the study of brass dezincification

It is possible to detect microscopically dezincification in artificial sea water at 50°C of hard or recrystallized 63/37 two phase (α + β) and single phase (α) brass samples, after simple immersion or after exposure in differential aeration cells. The minimum times to be able to detect the phenomenon are 2h and 1h respectively. This dezincification goes faster in α + β than in a single phase α-phase, and the process occurs more rapidly in differential aeration cells than by simple immersion. The aspect of dezincified zones is different for single phase α-brass, as compared to α + β brass. In the latter, dezincified zones tend to replace the β-phase of the structure and are thus very much confined to grain boundaries. Samples which do not present β-phase show dezincification spreading out over entire grains. Furthermore, metallographic observations point to a cathodic dezincification process in a brass-sea water-copper oxichloride brass cell, in which the oxichloride would polarize the brass electrode to the value of the reduction potential of copper. There should also exist, nevertheless, an anodic type process producing dezincification which would operate in a different way.

Corrosion Resistance of Various Ferrous and Non Ferrous Alloys in Refinery Equipments

The present study was made with the object of selecting suitable metals for refinery corrosion.The corrosion tests were conducted in a laboratory distillation apparatus equipped with vapor and condensate sections and controllable access of H2S, HCl, NH3 and H2O gases. It also could be operated both in atmospheric and vacuum pressures.Alloy steels are subject to severe pitting at the point where water condenses. Among the copper alloy, 70/30 and 60/40 brasses are dezincificated in thin layer while the beta phase (α+β) brass is attacked selectively. At high temperature, Cu-Ni alloys are attacked severely by sulfide but in the media where sulfide and chlorides coexists, alloys with Ni of more than 30% resists corrosion satisfactorily. Aluminum brass is more corrosive in media containing chloride but otherwise gives good service. When copper alloy are used in sulfide media, their copper content must be less than 80% and are in best condition when copper content is low in the range of 2 phase constitution.The test results suggest that copper alloys are suitable material for tubes of heat exchangers and coolers, following titanium and zirconiums which show maximum resistance but their resistance vary with operating conditions.