Cd Alloy Research Articles

The nature of special-mode softening and the mechanism of martensitic phase transition in β-phase alloys

Abstract The nature of the special mode in the β1 phases of NiAl and Au—Ag—Cd alloys is studied in detail from the viewpoint of the dynamic mechanism of the martensitic transition. The special mode becomes soft; the softening is responsible far the(112)[111] shear and hence for the formation of close-packed layers in the martensite. The origin of special-mode softening is an increased mode-mode correlation between the C′ and C 44 modes, i.e. an enhanced anharmonicity of the β1 lattice. Based on the results obtained, we propose a model of the transition processes of the β-phase alloys. We also discuss in detail the transition mechanism and show that the special-mode softening is an instability characteristic of the D1 lattice with a two-dimensional property induced by the C′ softening.

High-voltage, high-resolution electron microscopy of Au–Cd alloys. II. Double hexagonal long-period superstructures

Ordered structures of Au3Cd with a double hexagonal stacking sequence (4H) have been investigated by 1 MV electron microscopy in combination with many-beam dynamical calculations. One- and two-dimensional long-period superstructures (LPS) were observed at atomic level by high-resolution images with [001] incidence. The two-dimensional LPS was determined to be isomorphic with the Au77Mg23 structure. Two-dimensional LPS with stacking sequences 6Hand 9R were also found in the composition range 24–31 at.%Cd.

The structure of CuCd alloys obtained electrolytically on single-crystal copper cathodes

Tests were made on the structure of CuCd alloys produced on single-crystal copper cathodes with surfaces parallel to the (111), (110) and (100) planes. X-ray phase identification indicated the presence of the α phase in the form of a solid solution of cadmium in copper. The surface morphology of alloys obtained at a potential of up to -490 mV depends on the cathode type. Above this potential the surface morphology of the alloy is determined by the potential at which it is produced. In the low cathode potential range the crystallite orientation in the alloy is governed by twinning on the {111} planes of crystallites of epitaxial orientation relative to the cathode surface. We report here studies on the influence of cadmium on the twinning process and the formation of random orientation in the CuCd alloy crystallites.

Release of elastic strain energy as acoustic emission during the reverse thermoelastic phase transformation in Au-47.5 at .% Cd alloy

The objective of this paper is to present experimental evidence concerning the acoustic energy evolved during the heating and cooling phase changes in Au-47.5 at.% Cd polycrystals. The results are examined from the point of view of the stored elastic strain energy during the martensite formation, and the frictional work that is dissipated by the movement of martensite interfaces in either direction, upon heating and cooling.

The yield and flow stress of Cu1% Cd alloy

The tensile properties of a commercial copper-1% cadmium alloy have been investigated at 77, 300 and 420 K. The presence of cadmium produces a sharp yield point similar to that observed in mild steel and in aluminium-magnesium alloys. The yield and flow stresses of the material were found to obey the Hall-Petch relation and it is concluded that cadmium strengthens copper mainly by increasing the grain-size-dependent component of the strength. The alloy exhibits strain ageing. The interaction between a cadmium atom and dislocations in the alloy is considered and it is shown that the atomic size misfit interaction is dominant. It is concluded that cadmium atoms can strongly pin both dissociated edge and screw dislocations in copper. The value of the grain-size-dependent component of the yield strength at low temperatures and its temperature dependence suggest that the critical event at yield is the unpinning of dislocation sources within the grain boundaries. It also appears that this process is still important in the region of homogeneous deformation at higher strains, in contrast to what occurs in copper, where the grain-size-dependent component of the flow stress diminishes markedly with increasing plastic strain. A possible mechanism for the persistence of a strong grain-size effect in the alloy is suggested.

Effect of photoelectrode crystal structure on output stability of Cd(Se,Te)/polysulfide photoelectrochemical cells

Thin-film polycrystalline Cd(Se,Te) alloy photoelectrodes, which show output stability comparable to CdSe photoelectrodes when possessing the hexagonal (wurtzite) structure and which have optical band gaps similar to that of pure CdTe, are discussed.

Electrochemically deposited Schottky contacts of In, Cd and InCd alloy

Electrochemically deposited Schottky contacts of In, Cd and InCd alloy

Physical properties of liquid Li-Cd alloys and of the solid compound LiCd

The liquid alloys of Li and Cd, the electrical resistivity and the Knight shift have been measured over the entire concentration range. The resistivities can be explained fairly well within the Ziman diffraction model. The Knight shift versus concentration exhibits a sudden change of slope at the composition Li0.5Cd0.5. NMR linewidth measurements on the solid compound LiCd provided evidence for an appreciable mobility of the Li atoms through the lattice; the corresponding activation energy for diffusion is found to be 0.49+or-0.03 eV.

Rapid solidification and decomposition of a hypomonotectic Al-Cd alloy

Rapid solidification of Al-1.5at % Cd alloy can lead to a wide variety of morphologies. The sequence of the morphologies with increasing foil thickness is single phase → elongated cell → hexagonal cell → dendrite. Monotectic reaction ahead of the solid-liquid interface leads to a unique distribution of the cadmium particles. Models are proposed to explain the genesis of the distribution of these particles. The study of the decomposition behaviour confirms the existence of a preprecipitation stage. The G.P. zones are found to be spherical and lead to a precipitate-free zone near grain/cell boundaries. The coarsening of the precipitates at liquid temperatures takes place by the migration and coalescence of the droplets.

Thermodynamic studies and the phase diagram of the MgCd system

EMF measurements of the cell reaction: Mg(s)¦MgCl 2 in(LiCl-KCl) eut(l)¦MgCd (1) have been used to measure the partial molar free energies of MgCd liquid alloys in the composition range 0.042<x Mg<0.703 and at temperatures between 740 and 890 K. Partial molar enthalpies of cadmium measured in a Calvet calorimeter at 918 and 942 K were used for calculation of both the partial molar enthalpy of magnesium and integral molar enthalpies. The data from emf studies were also employed for phase diagram calculations. The emf results were coupled with independent calorimetric data to derive integral excess entropies which illustrate a correlation between the thermodynamic character and the structure of the liquid MgCd alloys.

Al-4%Cu-0.06%In合金における&amp;theta;&amp;prime;相の析出

The θ′ precipitation was studied in an Al-4%Cu-0.060%In alloy aged at 473 K by transmission electron microscopy, EDXS analysis, etc., to clarify the phenomenon of aging acceleration widely known in this alloy. The aging structures of Al-4%Cu-0.065%Sn and Al-4%Cu-0.096%Cd alloys as well as Al-4%Cu alloy were also studied.It was found that indium rich precipitates formed finely at an early stage of aging, resulting in the heterogeneous nucleation of θ′ on those precipitates. The results were common in three sorts of ternary alloys. However, some differences in hardening rate and peak hardness were observed among the alloys, and these differences were attributed to the difference in size and distribution-density of In, Sn or Cd rich precipitates acting as a nucleation site for θ′.

High Power Laser Effects on Unimplanted and Implanted Aluminium Single Crystals

Mechanisms involved in laser processing of ion implanted semiconductors have been extensively investigated (1,2). Relatively little work has been done on implanted metals (3,10). The liquid solid interface (melt front) velocity in metals (11,12) is much larger than that in Si. Therefore several nonequilibrium effects on recrystallization (6) solute segregation (9) and metastable phase formation (4,6,7) are observed. Such effects would depend on the melt front velocity, equilibrium phase diagram considerations (such as equilibrium segregation coefficient Ko, miscibility in licuid phase, intermediate phases etc.) and also on the as implanted nonequilibrium phase and defect structure. In this paper we present a study of the influence of some of these parameters during laser treatment of sincle crystals of virgin Al and dilute implanted alloys of Mo and Cd in Al.

The structure of CuCd alloys obtained electrolytically on monocrystal copper cathodes

AbstractTests were made on the structure of CuCd alloys obtained on single crystal copper cathodes with surfaces parallel to the (111), (110) and (100) planes. X‐ray phase identification indicated the presence of α‐phase in the form of a solid solution of cadmium in copper. In the low cathode potentials range alloy crystallite orientation is governed by twinning on the {111} planes of crystallites of epitaxial orientation relative to cathode surface. The surface morphology of alloys obtained up to potential −490 mV depend on cathode type. Above this potential value alloy surface morphology is determined by potential at which it is obtained.

Evidence for microporosity and dislocations in Pb(Cd) alloys from positron annihilation studies

The temperature dependence of lineshape parameters obtained from Doppler profile measurements (from 7 to 350 K) is presented for rolled and unrolled Pb, Pb(Cd), and Pb(Tl) alloys. It is demonstrated that positrons can be used to detect microporosity and dislocations in Pb(Cd) alloys. The porosity is greatly reduced by rolling. Positron trapping by the Pb(Cd) alloys in the as-worked state is attributable to dislocations.

The concentration dependence of CD diffusivity enhancement in dilute PBCD alloys

Solute diffusivity enhancement techniques were used to provide experimental evidence for the existence of interstitial-substitutional solute pairs. Diffusion of Cd in Pb--Cd alloys is thought to represent the substitutional extreme of the dissociative equilibrium.

Morphology and structure of bainite plates in the β’ phase of an Ag-45 at. pct Cd alloy

The morphology and structure of bainite plates which formed in the ordered bcc β’ phase of a Ag-45 at. pct Cd alloy at temperatures 160 to 300°C were studied by X-ray diffraction and transmission electron microscopy. Initially, the plates formed with a 3R stacking fault modulation of the fcc structure and contained a high density of random stacking faults. The stacking faults annealed out during a prolonged isothermal treatment, the structure gradually changing to a regular fcc. The orientation relationship between the bcc matrix and the fcc bainite was as follows: [1•11]b 0.7 deg from [0•11]f, [110]b 1.1 deg from [l00]f and [011]b 4.3 deg from the stacking fault plane pole [111]f. The habit plane of the bainite plates, determined by two surface trace analysis, was close to (3, 11, 12)b. The surface relief of the plates, examined by interference microscopy, was in the form of a simple tilt indicating an invariant plane strain transformation. The features of the transformation agreed with the predictions of the Bowles-MacKenzie theory of martensite formation. It was concluded that the morphology, structure and other characteristics of the freshly formed bainite plates were consistent with their formation by a thermally activated martensitic process.

In-Cd合金結晶の形状記憶

The structural change and the shape memory behavior in indium rich-(0∼6.20 at%) cadmium alloy crystals have been studied at both normal and elevated temperatures using X-ray and electron diffraction methods supplemented by optical microscopy. Polycrystals as well as single crystals are used as specimens. At 25±1°C the tetragonal phase changes to cubic at 5.6 at%Cd, and no metastable two-phase region is defined. Etched surfaces of tetragonal alloys show a banded structure parallel to {101} planes, as in the analogous indium-thallium alloys. On heating the alloys transform fct to fcc, and the fct\ ightleftarrowsfcc transformation is of the diffusionless type. Single crystals transform by the migration of a single interface, although the mobility is influenced by the history of mechanical deformation assigned to the specimen. In-(4.0∼5.5 at%)Cd alloys have a shape memory effect, but In-Cd alloys with more than 5.6 at%Cd does not show any shape recovery. X-ray topographic observations on heating show that the shape recovery is related with the migration of twin boundaries and also with the annihilation of the twinned structure. The shape memory effects in both In-Tl and In-Cd alloys are presented and compared with one another. Strong non-radial diffuse streak patterns are observed in X-ray and electron diffraction experiments. They are not streaks from elastic strain, but they are ascribed to thermal diffuse streaks which are related with lattice vibrations with low frequencies. The lattice stability and the microscopic nature of atom movements are discussed on the basis of lattice vibration.

Elastic constants of single crystals of the three phases of InPb alloys

In a study of the elastic behaviour of the InPb alloys, the elastic stiffness tensor components of crystals of each of the three phases (fct, c a > 1 ; fct, c a > 1 ; fcc) have been obtained as a function of temperature from pulse superposition measurements of ultrasonic wave velocities. Comparison of the elastic stiffness constants obtained for a fct ( c a > 1 ) 5 atm.% Pb alloy with those of In itself and those of InTl and InCd alloys, establishes for this phase that alloying with Pb, as with TI and Cd, enhances the softening of the acoustic [110] phonon mode, polarization [1 1 0] near the Brillouin zone centre. The elastic properties of a 17 atm.% Pb crystal, which is in the fct ( c a > 1 ) phase, are quite different from those shown by In alloys in the fct ( c a > 1 phase; in particular the response to a shear stress is remarkably isotropie: there is no phonon mode softening in this alloy. Neither is there softening of this mode (which corresponds at the zone centre to the shear stiffness 1 2 (C 11;C 12)) in crystals of the fee phase — in complete contrast to the dominating influence of the softening of 1 2 (C 11;C 12) in the InTl and InCd fee alloys. In fact for a fcc In-75 atm.% Pb alloy the anistropy ratio for shear 2C 44 (C 11C 12) is close to unity. The transitions between the three phases of the InPb alloys are markedly first order and acoustic mode softening has a much smaller influence on the elastic behaviour of the fct ( c a < 1 ) and fcc InPb alloys than it has on the fct ( c a < 1 ) InPb, InCd and InTl alloys.

Corrosion of electroplated CuCd alloys and its inhibition

The compounds o-, m- and p-phenylenediamine have been studied as possible inhibitors for use in the HNO 3 pickling of 94/6 and 80/20 CuCd electrodeposits on copper. Weight-loss and polarization data indicate that effective inhibition can be obtained for short periods of treatment and that effectiveness increases in the order p < m < o.

The electrical resistivity and deviations from Matthiessen's rule of single-crystal pure Cd and dilute Cd-Mg alloys

The authors have measured the electrical resistivities from 2K to 300K for eight Cd single crystals and eight Cd-Mg single crystals of two different concentrations. The measured densities of their specimens were typically 21/2% below the accepted X-ray densities. This is attributed to small bubbles in the specimens and the authors have made an appropriate correction to obtain the resistivity values. The ice point resistivities for Cd were found to be rho i//=7.81(+or-0.03) mu Omega cm and rho i perpendicular to =6.30(+or-0.03) mu Omega cm. Deviations from Matthiessen's rule Delta which were calculated from these measurements both confirm and clarify earlier experimental results for polycrystalline specimens and agree qualitatively with a theoretical calculation for single crystals.