Cold-worked Samples Research Articles

Valence Transformation of Eu Atoms Due to Defect Association in Cold-Worked EuMg Alloys

Magnetic susceptibility and Moessbauer-effect measurements on a series of dilute alloys of Eu in Mg have been performed. In strain-free samples the Eu ions are divalent, but in cold-worked samples a large fraction are converted to the trivalent state. Isochronal annealing studies suggest that this is related to the trapping of dislocation on impurity clusters with the valence change occurring because of the strain field of the dislocation.

The structure-property relationships in evaporated thick films of alumina-dispersed copper

The properties of dispersion-strengthened materials produced by the high rate physical vapor deposition technique were studied. Emphasis was on the copper-alumina system. For this study room temperature properties were measured. As-deposited microhardness and also stability characteristics (as established by hardness tests after annealing at various temperatures following a cold-rolling treatment) were determined. These were correlated with metallographic examinations. Tensile tests were performed on the as-deposited materials and also on cold-worked samples. Fractography was done by scanning electron microscopy. Thick films (up to 0.2 cm) were prepared by dual-source evaporation (electron beam healing) and condensation on a stationary substrate preheated to the desired deposition temperature. Deposition rates of about 4000 Å s −1 were used. Fine dispersions led to a high as-deposited hardness, about six times the value for pure copper with less than 2 vol.% of alumina. Although annealing caused possible coarsening of the oxide particles, the hardness did not fall appreciably when the films were kept at 0.94 T m for 1 h. The stability experiment was very encouraging. With only about 0.3 vol.% alumina the hardness remained at about three times the value for pure copper even on annealing (after 50% cold-rolling) up to almost the melting point of copper. Transmission electron microscopy showed fine particles of alumina (80 Å) after prolonged annealing at 0.79 T m. Optical micrographs revealed very little recrystallization of the matrix. The tensile strenght of the as-deposited material (with only 0.5 vol.% alumina) was 50% greater than that of pure copper. For the cold-rolled deposits, about 1 vol.% alumina gave a 50% higher ultimate tensile strength compared with pure copper. Fractography showed a consistently ductile mode of failure on the microscopic level despite apparent brittle behavior from a macroscopic viewpoint. The results were compared with a commercial powder metallurgy product and were found to be equivalent if not better.

Mechanism of voltage generation during phase change of FeS single crystals

Electrical resistivity measurements have been performed for annealed Cu–Sn wires with compositions of 2, 5, 10 and 13.5 wt% Sn from room temperature to 700 °C. The annealing behaviour of cold-worked samples of these compositions has been investigated using resistometry, microhardness and optical microscopy. All samples undergo a hardness reduction of around 100 HV (300 g) on annealing. However, the room temperature resistivities differ greatly between the cold-worked and annealed condition only for the 10 and 13.5 wt% Sn samples, for which large resistance changes occur in the 300–500 °C range. Recrystallisation is delayed to around 400 °C in the high-tin samples; interaction between annealing and Cu3Sn (epsilon phase) precipitation is proposed as an explanation for the resistivity behaviour of these samples. The implications of these resistivity results for resistometric monitoring and optimisation of bronze route Nb3Sn superconducting wires are summarised.

Ordering kinetics of cold-worked Ni 4Mo

The present study reports the results of the effects of cold-work on an alloy undergoing an order - disorder transformation. The particular system chosen was the Ni 4Mo composition which possesses an ordered b.c.t. structure below 868°C, while above this critical temperature a disordered f.c.c. lattice is present. By analysing X-ray diffraction, metallography and hardness measurements, it has been possible to compare the kinetics of ordering of a 60% deformed sample with an asquenched alloy. Though in both cases a heterogenous growth mode was operative, the cold-worked sample on a macroscopic scale exhibited a much more uniform domain size than did the as-quenched alloy. Moreover, this latter regular microstructure had faster growth kinetics than had the as-quenched alloy.

Effects of low-temperature fast-neutron irradiation on ac losses in NbTi

The complex magnetic permeability of Nb-44 at.% Ti has been measured using a modified Hartshorn ac bridge and a lock-in amplifier. The out-of-phase signal can be directly related to the energy losses, and critical current can be calculated using the Bean model. Samples were irradiated in a fission neutron spectrum to a dose of 3.2×1018 neutron/cm2. All measurements were taken in situ at approximately 4.5 °K in an external magnetic field continuously swept to 6.7 kOe while applying ac magnetic fields at 88 Hz with amplitudes between 8 and 500 Oe. Irradiations and measurements were performed on an annealed and a cold-worked sample of the alloy. For the annealed sample, no changes were observed in VL and thus in Jc after 8.2×1017 neutron/cm2 and after an anneal to 320 °K. A decrease of approximately 8% was observed in Jc for the cold-worked sample after 3.2×1018 neutron/cm2. One-half of this decrease was recovered by 270 °K.

Formation and growth of cu 3au ii in a deformed matrix

Copper-gold alloys containing 30 at.% gold were converted into powder, by filing at room temperature and at 77K, and into plates by rolling at room temperature (reduction in area 90%). The ordering was studied by means of X-ray diffraction techniques. The powder samples in the as-deformed or recrystallized condition were annealed at different temperatures and iced-brine quenched. In filings, prepared at room temperature, the satellites and the central superstructure reflection grew at about the same rate, implying the direct formation of Cu 3Au II from the SRO-state and not via the Cu 3Au I-I phase. The degree of order was lower in the cold-worked samples, whereas the Cu 3Au II-content appears to be little affected by cold-work. Of the plates, annealed for various times at 361°C, the microhardness vs time curve displays two maxima, the texture parameter T 220, i.e. the ratio of peak intensities, varies in phase with the 111 microhardness curve and recrystallization occurs immediately beyond each maximum. In between the two maxima, the original texture of the cold-worked sample reappears and from the second maximum on a cube texture develops. Cu 3Au II is definitely present in a cold-worked plate after 32 hr annealing, whereas in an initially recrystallized plate, this phase is already clearly visible after 8 hr annealing.

Line broadening studies of deformation in MoTe2

Deformed (cold-worked) samples of molybdenum ditelluride (MoTe2) — a six-layered h c p structure — have been found to exhibit symmetrical broadening in their X-ray diffraction profiles corresponding toH-K=3N±1 reflections. Integral breadth measurements have been used to analyse the line profiles in a manner as it is applicable to a simple two layered h c p structure. The reason for such a mode of approach has been discussed. On the presumption that the growth faults in this material are negligibly small, the deformation stacking faults probability due to the glide on Te/Te slip planes only is found to be ≃ 0.144±0.010, and the dislocation density in the bulk material is estimated to be ≃(2.66±0.36)×1011 cm cm−3.

Radiation blistering of polycrystalline niobium by helium-ion implantation

The radiation blistering of polycrystalline niobium surfaces at room temperature has been investigated for different doses of helium ions implanted at 0.5 MeV and for different amounts of initial defect structure in the samples. The cold-worked samples show large blisters (up to 500 μm in diameter), many of which are ruptured. In samples annealed before irradiation, the blistering at low doses (0.1 C/cm2) was lower than in the cold-worked sample, but at a higher dose (1.0 C/cm2) the blistering was even greater. The observation of interconnecting bubbles offers a possible explanation for the formation of such large blisters at low temperatures.

Blistering of polycrystalline and monocrystalline niobium

Abstract Radiation blistering of niobium surfaces has been investigated for normally incident He+ and D+ projectiles. For the He+, the bombarding energies were 0.5 and 1.5 MeV, the targets were both monocrystalline and polycrystalline niobium at room temperature and at 900°C, and the total dose was from 0.01 to 1.0 C/cm2. For cold-worked samples at room temperature, 0.5-MeV He+ ions produced large blisters (up to 500 μm in diameter), many of which were ruptured; 1.5-MeV He+ ion implantation produced one big blister covering most of the irradiated area. For the D+ ion implantation, the bombarding energies were 0.250 and 0.5 MeV and the targets were all polycrystalline. Implanting 0.250-MeV D+ ions in annealed polycrystalline Nb at 700°C produced small blisters for doses ranging from 1.6 to 3.0 C/cm2. Preliminary results on the skin thicknesses of ruptured blisters indicate a close relationship between the thickness and both the projected range of the ions and the peak in the defect distributions.

Dislocation damping in high purity molybdenum

Dislocation interstitial interactions in high purity molybdenum have been investigated by means of internal friction measurements. A Marx piezoelectric composite oscillator with a resonant frequency of 50 kHz was used to measure the log decrement as a function of time, temperature, and strain amplitude. Measurements on slightly cold worked samples show that at temperatures above 100°C the amplitude-independent damping decreases with time. This effect has been explained in terms of the diffusion of interstitial nitrogen to the dislocation lines pinning them and rendering them immobile. An activation energy for the process has been found to be between 1.12 and 1.18 eV which agrees with the diffusional energy of interstitial nitrogen in molybdenum. In the two purer grades of molybdenum, a maximum was observed in the amplitude-dependent damping. The damping maximum was observed after annealed samples were deformed at room temperature. The behavior of the damping maximum has been studied as a function of temperature and various thermomechanical treatments. The damping maximum is attributed to the motion of dislocations produced by deformation, which have a very low concentration of breakable pinning points along the dislocation lines.

Contactless measurement of recovery and recrystallization in steel

The mechanical and magnetic properties of iron are closely related. In particular, cold working an annealed sample increases the mechanical hardness and decreases the magnetic permeability; conversely, recrystallization of the cold-worked sample will return these properties to their original levels. At any given level of applied fieldHa the larger the permeability, the larger is the magnetization and the external fieldHex of the specimen at any point external to the specimen. The curves of Fig. 1 show this effect for a variety of applied fields. It follows that any metallurgical process that changes the permeability can be continuously monitored by measuring the external field of the specimen. This study is directed at recovery and recrystallization.

A diffraction study of the annealing of cold-worked Cu3Au

X-ray diffraction was used to study the recrystallization and ordering behavior of cold-worked Cu3Au annealed below the critical temperature. Samples of the alloy initially disordered by quenching and then cold-worked by filing were found to establish a high degree of long-range order very rapidly at temperatures in the range 300° to 375°C. The kinetics of antiphase domain growth were found to be essentially the same as previously established for the alloy having no cold work after thermal disordering. However, for a given annealing treatment, the average antiphase domain size in the initially cold-worked samples waslarger than that in initially disordered samples which had not been cold-worked. This observation is contrary to results of previous investigators and the reasons for their incorrect conclusions are discussed. Measurements of the particle size and rms microstrains established that recrystallization is retarded as the annealing temperature approaches the critical temperature.

Mechanism of scc of α-brass in Mattsson's solution under potentiostatic conditions

SCC of α-brass in Mattsson's solution has been studied under potentiostatic anodic and cathodic polarization. In annealed samples, anodic polarization brings in a minimum in cracking time accompanied by a transition in cracking mode from intergranular to transgranular. The range of potential giving maximum susceptibility to cracking has been found to be independent of Cu content and pH of the test solution, but dependent on cold work. Cathodic polarization increases the resistance to cracking, and in cold-worked samples, where the cracking is initially transgranular, a transition to intergranular has been observed on cathodic polarization. SCC has been encountered also in a non-Cu-containing solution. These observations strongly suggest a mechanism based on a shift in active anodic and cathodic sites on polarization and adsorption playing an important role in the cracking process.

Changes in Electrical Resistance of α-Brass During Stress-Corrosion Cracking

The changes in electrical resistance of α-brass during stress-corrosion cracking showed marked variation at different stages. The number and depth of cracks were determined at definite time intervals and the results compared with the change in resistance. The tests indicated the presence of an incubation period in annealed samples but not in cold-worked samples.

Coercive force and structure in a Co-Fe-Au alloy

Strip samples of 82 Co-12 Fe-6 Au alloy were solution annealed and quenched to produce a supersaturated γ (fcc) structure. The samples were then cold worked to 50, 75, and 90 pet R.A. by rolling. Magnetic measurements showed that cold work increasedHc from the 1 oe level in well annealed samples to about 5 oe for all amounts of cold work, and that annealing of the cold worked samples further increasedH1 to maximum values of 9, 11, and 13 oe for the 50, 75, and 90 pet cold worked samples, respectively. The structural changes produced by annealing were followed quantitatively by light metallography. The progress of a discontinuous precipitation reaction, which simultaneously relieved the supersaturation of the solution treated matrix and effectively recrystallized the cold worked matrix was found to correlate well with the measured increases in coercive force. Electron transmission and diffraction verified that fine particles of gold on the order of 1000A in diam were formed by the discontinuous precipitation.

Strain induced knight shift in rhodium metal

The second moment of N.M.R. lines of several cold worked samples are linearly related to the mean square distortion, measured by analysis of X-ray diffraction line shapes. This effect can be understood as coming partly from the variation of the susceptibility with shear stress and partly from dipole-dipole coupling between d electrons and the Rh nuclei.

Strain hardening of martensite in high-nickel steels

After 15% cold deformation (rolling) of the quenched samples the hardness increased from HV 500 to HV 560 (Fig. la). Subsequent heating at 100~ for 1 h induces further increase of the hardness from I-IV 560 to HV 605. Tempering at 150 and 200~ has almost no effect on the hardness, and only at higher temperatures does the hardness decrease. At all tempering temperatures the hardness of the cold worked samples remained higher than for the undeformed samples. The difference persisted after the reverse transformation, which leads to the conclusion that a portion of the structural defects created by cold working is retained up to high temperatures. After deformation of the quenched samples the width of (220) not only does not increase but even decreases somewhat (Fig. lb). Heating at 100-150~ leads to further reduction in the width of (220). At tempering temperatures above 200-250~ the line width decreases sharply. The reduced width of the martensite line resulting from deformation may be due to such processes as reduction of the carbon concentration in the solid solution on formation of carbides, the interaction of carbon atoms with dislocations, and disordering of the solid solution of carbon in the tetragonal lattice of martensite (movement of carbon from one pore to another within the lattice) [9]. The first two processes can occur only with sufficient mobility of the carbon atoms. In steels with high nickel concentrations both processes can occur at a fairly rapid rate at room temperature. In steel with 0.45% C and 0.22% Ni the carbide precipitates after tempering at 60~ attain such sizes that they can be seen in thin foils in the electron microscope [10]. HV

Medical diagnosis with ultrasound — Some new equipment: Bellamy, R.J. and Strickland, R.G. Biomedical engineering, 2, no. 6, p. 262 (1967)

The properties of dispersion-strengthened materials produced by the high rate physical vapor deposition technique were studied. Emphasis was on the copper-alumina system.For this study room temperature properties were measured. As-deposited microhardness and also stability characteristics (as established by hardness tests after annealing at various temperatures following a cold-rolling treatment) were determined. These were correlated with metallographic examinations. Tensile tests were performed on the as-deposited materials and also on cold-worked samples. Fractography was done by scanning electron microscopy.Thick films (up to 0.2 cm) were prepared by dual-source evaporation (electron beam healing) and condensation on a stationary substrate preheated to the desired deposition temperature. Deposition rates of about 4000 Å s−1 were used. Fine dispersions led to a high as-deposited hardness, about six times the value for pure copper with less than 2 vol.% of alumina. Although annealing caused possible coarsening of the oxide particles, the hardness did not fall appreciably when the films were kept at 0.94Tm for 1 h. The stability experiment was very encouraging. With only about 0.3 vol.% alumina the hardness remained at about three times the value for pure copper even on annealing (after 50% cold-rolling) up to almost the melting point of copper. Transmission electron microscopy showed fine particles of alumina (80 Å) after prolonged annealing at 0.79Tm. Optical micrographs revealed very little recrystallization of the matrix.The tensile strenght of the as-deposited material (with only 0.5 vol.% alumina) was 50% greater than that of pure copper. For the cold-rolled deposits, about 1 vol.% alumina gave a 50% higher ultimate tensile strength compared with pure copper. Fractography showed a consistently ductile mode of failure on the microscopic level despite apparent brittle behavior from a macroscopic viewpoint. The results were compared with a commercial powder metallurgy product and were found to be equivalent if not better.

Influence of ultrasonics on some metallurgical processes: Fairbanks, H.V. IEEE transactions on sonics and ultrasonics, SU-14, no. 2, p. 53 (1967)

The properties of dispersion-strengthened materials produced by the high rate physical vapor deposition technique were studied. Emphasis was on the copper-alumina system.For this study room temperature properties were measured. As-deposited microhardness and also stability characteristics (as established by hardness tests after annealing at various temperatures following a cold-rolling treatment) were determined. These were correlated with metallographic examinations. Tensile tests were performed on the as-deposited materials and also on cold-worked samples. Fractography was done by scanning electron microscopy.Thick films (up to 0.2 cm) were prepared by dual-source evaporation (electron beam healing) and condensation on a stationary substrate preheated to the desired deposition temperature. Deposition rates of about 4000 Å s−1 were used. Fine dispersions led to a high as-deposited hardness, about six times the value for pure copper with less than 2 vol.% of alumina. Although annealing caused possible coarsening of the oxide particles, the hardness did not fall appreciably when the films were kept at 0.94Tm for 1 h. The stability experiment was very encouraging. With only about 0.3 vol.% alumina the hardness remained at about three times the value for pure copper even on annealing (after 50% cold-rolling) up to almost the melting point of copper. Transmission electron microscopy showed fine particles of alumina (80 Å) after prolonged annealing at 0.79Tm. Optical micrographs revealed very little recrystallization of the matrix.The tensile strenght of the as-deposited material (with only 0.5 vol.% alumina) was 50% greater than that of pure copper. For the cold-rolled deposits, about 1 vol.% alumina gave a 50% higher ultimate tensile strength compared with pure copper. Fractography showed a consistently ductile mode of failure on the microscopic level despite apparent brittle behavior from a macroscopic viewpoint. The results were compared with a commercial powder metallurgy product and were found to be equivalent if not better.

Results of fourier analysis and line breadth measurements on molybdenum filings

Abstract X-ray photographic technique with nickel filtered and crystal monochromated CuKα radiation has been used to record (110), (220), (200) and (400) reflections from molybdenum filings. Stokes' method has been used to apply a correction for instrumental broadening. The line profiles have been analysed with different methods. The ratio of domain sizes in two directionsL(110) : L(100), is approximately 0•97. The slight anisotropy in particle sizes and lattice strains exists even in the annealed state. While no evidence of faulting could be found, the composite broadening is attributed to particle size and lattice strains. The integrated intensities of line profiles obtained from cold-worked and annealed samples are found to be the same within the limits of experimental accuracy.