Copper-titanium Alloys Research Articles

Sputtering and radiation-enhanced segregation in amorphous CuTi alloys

Binary amorphous copper-titanium alloys of compositions 44, 53, 65 and 69 at% copper were sputtered with 2 keV Ar + ions. The surface concentrations were then determined by Auger electron spectroscopy and ion scattering spectrometry. It was found that Cu is sputtered preferentially as it segregates to the surface. A recently developed model for radiation-enhanced surface segregation was used to fit the experimental data. The segregation energy decreases with increasing Cu concentration from 2500 Jmol −1 to zero for the highest concentration, in qualitative agreement with several predictions on the segregating species in the alloy. The radiation-enhanced diffusion coefficients have values in the range (2–3) × 10 −20 m 2 s . From the concentration profiles the depth of the altered layer was estimated to about 4 nm which coincides well with the range of the defect distribution caused by the argon ions according to TRIM calculations. A Cu Ti sputtering ratio of 6 was needed for the best possible fit of the results.

Effect of Radiation on the Corrosion of Candidate Materials for Nuclear Waste Containers

ABSTRACTThe published information on the effect of radiation on the corrosion of potential waste container materials is reviewed. The materials discussed are irons and carbon steels, copper and copper alloys, stainless steels, nickel-based alloys, and titanium alloys. In general, a dose rate of >5 Gy·h-1 is required to accelerate the general corrosion of corrosionallowance materials. The effects of radiation on the localized corrosion of corrosion-resistant materials appear to be contradictory. In some cases, localized corrosion is induced, whereas in others it is inhibited.

Some observations on the wetting and bonding of nitride ceramics

Several series of experiments have been conducted to gain information about the wettability of AlN, BN, Si3N4 and two sialon ceramics by potential braze materials. It was possible to achieve wetting of all five ceramics using aluminium, copper-titanium alloys, and a Ag-28Cu-2Ti alloy. Wetting by aluminium and the Ag-28Cu-2Ti alloy was usually good. Both wetting and non-wetting alloys containing titanium reacted to form TiN and it is argued that the achievement of wettability is associated with a certain degree of hypostoichiometry. While aluminium should also have reacted, no clear evidence was obtained. In supplementary experiments it was found that bonds formed by brazing with aluminium at 1000 °C could have shear strengths as great as 60MPa. Although the experimental work was preliminary in nature, it suggested that good brazing systems could be developed.

Pressure and concentration dependence of the quantum corrections to the resistivity in copper-titanium alloys

We present a full set of pressure- and temperature-dependent resistivity data for the regions 0 < P < 10 GPa, 1.4 < T < 30 K, and 43 < x < 88, Here, x denotes the concentration of the amorphous alloy Cu{sub x}Ti{sub 100-x}. These results are analyzed in terms of a temperature-independent Boltzmann resistivity and additive quantum corrections, such as the quantum interference and the Coulomb correction. It is shown how the various parameters involved in these contributions vary with pressure. Certain arguments are given in an effort to understand qualitatively the observed behavior.

The wetting and bonding of Si 3N 4 by copper-titanium alloys with other elements

The wettability of pressureless sintered Si 3N 4 by ternary alloys of copper, titanium and aluminium, silicon and yttrium has been investigated in vacuum at 1160°C. The bond strength of Si 3N 4 to itself was also evaluated by compressive shear test. While the wettability is influenced by the titanium activity, it may be overcome by the surface tension of the alloy. Titanium activity is lowered when aluminium and silicon, which have high interactions with titanium, are added. On the other hand, titanium activity is enhanced when yttrium, which has a low interaction with titanium, is added. It was found that TiN and various Ti-silicides formed in the reaction layer. The type and position of the reaction products are changed by the titanium activity, according to the alloying additions and their contents. Higher strength was obtained with the addition of aluminium and thin reaction layer formation. As the reaction temperature and time were increased, shear strength decreased due to the increased thickness of the reaction layer and the formation of a brittle phase in spite of improved wettability. Aluminium appeared to be the most effective element for the control of interfacial reaction. Yttrium addition (less than about 5 %wt) was also very effective in increasing strength under very low concentrations of titanium (less than about 5 %wt).

The Hall effect and resistivity of amorphous copper-titanium alloys

The authors have studied the resistivity and Hall effect of three amorphous CuxTi1-x alloys between 1.24 and 300 K. The use of thin film samples (prepared by RF magnetron sputtering) and a sensitive AC technique for the Hall coefficient allowed an accurate measurement of the temperature dependence of both quantities to be made. They find good agreement with predictions based upon electron-electron correlation theories.

Tunneling microscopy from 300 to 4.2 K

A scanning tunneling microscope (STM) has been developed for operation over the full temperature range from 300 to 4.2 K. At room temperature, the instrument has been used to produce topographic images of grain structure in a copper-titanium alloy foil and of atomic structure on a Pt(100) surface. At low temperatures, the instrument can be used in a new spectroscopic mode, one which combines the high spatial resolution of the STM with the existing technique of electron tunneling spectroscopy. This new capability has been demonstrated by using the microscope to probe spatial variations in the superconducting character of a niobium-tin alloy film.

Ａｒ‐Ｎ２ガスシールド溶接における銅溶接金属の機械的性質および焼鈍組織に及ぼす窒素ならびにチタンの影響

Oxygen-free copper plates were welded with copper and copper-titanium alloy electrode wires using argon-nitrogen gas mixture shielding. The effects of the nitrogen percent (N2%) in the shielding gas and the titanium content (Ti%) of the electrode wire on mechanical properties and annealed structures of the weld metal were examined. The Vickers hardness increases with Ti% of the electrode wire. The yield stress and the tensile strength of the weld metal increase with Ti% of the electrode wire, while the elongation and the reduction of area show maximum at about 0.5%Ti in the wire. Those tensile properties of the weld metal are independent of N2% in the shielding gas. β' precipitates are observed in some of the weld metals annealed at 573-1173 K for 3.6 ks. The precipitation is the most remarkable after annealing at 700-800 K, and the amount of the precipitates increases with increase of Ti% in the wire and with decrease of N2% in the shielding gas. The Vickers hardness increases with the amount of the precipitates.

Wetting and contact reaction in systems of rare-earth oxides with copper-titanium alloys

The wetting angles of rare-earth metal oxides of the yttrium group with copper and copper-titanium alloys are higher than for Al2O3, which qualitatively agrees with the greater changes (in absolute values) in the free Gibbs energies for the formation of rare-earth oxides in comparison with Al2O3.

The cellular reaction in dilute copper-titanium alloys

A review is made of the various mechanistic models for the initiation of the cellular reaction. Observations of the production of theβ phase in dilute copper-titanium alloys are reported, and it is noted that the Widmanstatten product and small, recently nucleated intermediate cellular plates adhere strictly not only to the (111)α//(010)β [ 110]α //[001]β orientation relationship, but also to the favorable (111)α//(010)β habit plane. The plates in cellular colonies developed at lower transformation temperatures (and thus higher supercoolings) show appreciable deviations from the latter interface plane, though the orientation relationship is still obeyed. Three different initiation mechanisms for cellular precipitate are observed. The ‘pucker’ and the ‘conventional’ routes are found to operate, and in addition a mechanism relying on the preexistence of Widmanstatten plates has been identified. The intermediate level of crystallographic specificity displayed by the coppertitanium system is suggested, therefore, to give rise to a high.probability of cellular precipitation. It is shown that the reaction can proceed under the action of very low driving forces.

Influence of vanadium on structure and kinetic transformations in Cu-Ti alloys

AbstractChemical, metallographic, and X-ray diffraction analyses and electrical resistivity and Vickers hardness measurements were used to determine the influence of vanadium (up to 0·23 wt-%) on the structure and kinetic transformations of copper-titanium alloys which take place during the process of high-temperature aging at 300°–600°C. It was found that vanadium retards the continuous precipitation of the intermediate phase β′ and accelerates the discontinuous precipitation of(α+β).

The structure of the β-phase in dilute copper–titanium alloys

An experimental study is made of the β-phase in a copper alloy containing 5.7 at% titanium. A number of electron microscope techniques are used and in particular a large collection of diffraction data from the β-phase is obtained. It is shown that this data cannot be systematically interpreted within the framework of the usual choice of unit cell (due to Karlsson) but that the cell shape proposed by Pfeifer et al. is correct for the data presented here and in previous papers. Some modifications to the atomic positions within the Pfeifer et al. cell are required in order to account for the overall distribution of reflections in these diffraction patterns. Die β-Phase einer Kupferlegierung mit 5,7 at% Titan wird experimentell untersucht. Mehrere elektronenmikroskopische Techniken werden benutzt und insbesondere eine grose Zahl von Beugungswerten von der β-Phase gesammelt. Es wird gezeigt, das diese Daten nicht systematisch interpretiert werden konnen im Rahmen der gewohnlich benutzten Einheitszelle (nach Karlsson), das jedoch die von Pfeifer et al. vorgeschlagene Zellenform fur die hier vorgestellten und in fruheren Arbeiten erhaltenen Daten korrekt ist. Einige Modifikationen bezuglich der Atomlagen innerhalb der Zelle von Pfeifer et al. sind erforderlich, um die Gesamtverteilung der Reflexe in diesen Beugungsdiagrammen zu erklaren.

Preliminary observations of the flow and fracture of copper-titanium alloy single crystals containing coherent precipitates

1. 1. Copper-Titanium alloy single crystals containing 1 wt.% Titanium oriented for single slip were tested in tension. The aged crystals containing coherent precipitates exhibited distinct yield points (probably geometrical in origin) and deformed extensively by single slip on the primary slip system. 2. 2. Profuse secondary slip commenced abruptly in the vicinity of the symmetry boundary resulting in intense localized flow and plastic instability. 3. 3. Twinning was observed to occur in the necked region following the onset of coarse secondary slip. 4. 4. Final separation occurred by a ductile fracture mode with the geometry of the fracture surface varying with particle size and strength.

Spinodal decomposition, ordering, and discontinuous precipitation in deformed and aged copper-titanium alloys

Phase transformations in quenched, deformed, and aged copper-titanium alloys containing up to 5,6 at.-% Ti were studied by means of hardness measurements and electron microscope examinations of thin foils. The modulation wavelength showed a linear relationship with the logarithm of the aging time. Deformation caused a slower increase of the modulation wavelength and a reduction of the critical spinodal temperature Te. The formation of the Dla superlattice was observed in the titanium-rich modulations. The spatial distribution of modulations is discussed in terms of the ordered domain shape. The formation of an ordered structure is not observed in highly deformed specimens in which heterogeneous precipitation of the transition tetragonal a' or stable β′ phases occurs on dislocations and other structural defects. The nucleation of discontinuous precipitation occurs in deformed alloys not only at grain boundaries but also at deformation bands and highly misoriented subgrain boundaries. The increased number of nucleation sites affects the kinetics of discontinuous decomposition. Depending on the degree of deformation and aging temperature the nucleation of recrystallization, or discontinuous precipitation, was observed. The mechanisms of recrystallization are discussed.

Diffusion of titanium in copper

Interdiffusion coefficients in copper-titanium alloys have been determined by Matano's method in the temperature range between 973 and 1283 K on (pure Cu)-(Cu-1.98 at. pct Ti alloy) and (pure Cu)-(Cu-2.91 at. pct Ti alloy) couples. Temperature dependence of the impurity diffusion coefficient of titanium in copper, determined by extrapolation of the concentration dependence of the interdiffusion coefficient to zero mole fraction of titanium, is expressed by the following Arrhenius equation along with the probable errors:D Ti/Cu=(0.693 −0.135 +0.169 )×10−4exp[−(196±2)kJ mol−1/RT] m2/s. The difference in the activation energies for the impurity diffusion of the 3d-transition metals and self-diffusion in copper has been calculated by applying LeClaire's model with the oscillating potential of the impurity atom in copper. The calculated values agree well with the experimental values including the present one.

Electron microscope study of the effect of deformation on precipitation and recrystallization in copper-titanium alloys

Structural changes occurring during aging of deformed as-quenched copper-titanium alloys were studied by means of hardness measurements and thin foil electron microscope examination. It was demonstrated that the average subboundary misorientation tends to increase with increasing strain values. The development and microstructure of deformation bands and their role in precipitation and recrystallization are discussed. Depending on the degree of deformation and aging temperature nucleation of either recrystallized grains or discontinuous precipitates was observed. After deformation lower than 30 pct the formation of recrystallization nuclei proceeds according to the strain induced boundary migration mechanism. After higher deformation recrystallization nuclei are formed mostly within deformation bands. A schematic TTT diagram is proposed, illustrating the sequence of various phase transformations that occur in the alloys investigated. The tendency of TTT curves shifting with increasing deformation, and a range of proposed heat treatment are discussed. It is shown that in deformed alloys spinodal decomposition occurs at aging temperatures lower than those in the underformed ones. Coarsening of modulations is affected by heterogeneous α' and β' phases precipitation, which is followed by discontinuous precipitation of α and β' phases of determined crystallographic relationship.

Ordering in copper-titanium alloys

Ordering in copper-titanium alloys

Reply to “the crystal structure of the metastable precipitate in copper-based copper-titanium alloys”

Reply to “the crystal structure of the metastable precipitate in copper-based copper-titanium alloys”

The crystal structure of the metastable precipitate in copper-based copper-titanium alloys

The crystal structure of the metastable precipitate in copper-based copper-titanium alloys

A high resolution electron microscopy study of spinodal decomposition and coarsening in copper-titanium alloys : By D. E. Laughlin; Thesis, Massachusetts Institute of Technology (Supervisor: J. W. Cahn)

A high resolution electron microscopy study of spinodal decomposition and coarsening in copper-titanium alloys : By D. E. Laughlin; Thesis, Massachusetts Institute of Technology (Supervisor: J. W. Cahn)