Recovery Of Electrical Resistivity Research Articles

Short-range order in Fe-Cr alloys irradiated with electrons at low temperatures and cr solubility in α-iron near 270 K

Chromium has limited solubility in -iron. It is shown that unsaturated Fe-Cr alloys should demonstrate short-range ordering (i.e. tendency to neighboring of Fe and Cr atoms). The type of short-range ordering in several Fe-Cr alloys is revealed from the data on the recovery of residual electrical resistivity after low temperature electron irradiation at sufficiently low temperatures. The combined consideration of the data on short-range ordering and chromium solubility at 570 K (Scr. Mater. 2014 v. 74, p. 48 and ibid 2016 v. 122, p. 31) gives the confidence interval for the solubility limit near 270 K equal to 8.8±0.4 at. % Cr.

The influence of 2 at. % Si addition on the annealing of radiation-induced defects in the Fe-13Cr alloy

The paper presents data on electrical resistivity recovery in the Fe-13.4Cr and Fe13.6Cr-1.9Si alloys during isochronal annealing after 5 MeV electron irradiation below 77 K. Long-range migration of radiation-induced defects starts slightly above 200 K in Fe-13.4Cr. The silicon addition in Fe13.6Cr-1.9Si leads to immobilization of Frenkel pair defects thus making the peaks of the stages of the onset of long-range migration shift towards high temperatures up to 370 K and 420 K for self-interstitial atoms and vacancies, respectively. This finding confirms the data obtained earlier for Fe16Cr-Si alloys by means of positron annihilation technique (JNM 508(2018) 100–106) on trapping of radiation-induced defects on Si agglomerates (clusters consisting of several silicon atoms) formed during defect migration.

A multiscale study of the production and recombination of closely correlated defects from irradiation-induced higher order recoils in beryllium

Beryllium is considered as a neutron multiplier in the self-sustained fuel cycles of future fusion reactors like ITER and DEMO, thus the retention of tritium generated in transmutation events in beryllium is crucial for the operational safety of such devices. As tritium readily interacts with microstructural defects produced under neutron irradiation, its retention depends on the evolution of the microstructure. Thus, physics-based models to understand and ultimately predict the tritium retention behavior have to comprise the generation and recombination dynamics of such defects. Therefore, the generation and recombination of the most simple defects, i.e. closely correlated as well as separated Frenkel pairs, as produced at the very end of collision cascade branches are considered in this work. To that end, DFT calculations are performed to determine threshold displacement energies, typical closely correlated pair configurations, the volume of spontaneous recombination, and recombination energy barriers. On the basis of these atomic-scale results, rate-based recovery models are derived to simulate electrical resistivity recovery experiments. The proposed models suggest that the principal recovery peak of beryllium is associated with the onset of intra-basal self-interstitial diffusion. This association is found to hold for the principal recovery peak of zirconium as well and it is thus concluded it is likely to generalize to many hcp metals with smaller than ideal c to a ratios.

Proton irradiation and resistivity recovery in stages I & II of pure and carbon-doped Fe

Pure and C-doped Fe specimens were irradiated with 5 MeV protons at cryogenic temperature at the NCSR-"Demokritos" TANDEM accelerator in order to investigate the interactions between carbon atoms and radiation defects. During the subsequent post-irradiation isochronal annealing up to 180 K the defects start to migrate and interact either mutually or with the C impurities. The defect evolution is observed by in-situ electrical resistivity recovery measurements. Comparison of results from pure and C-doped Fe specimens reveals the effect of C solute atoms on the defect kinetics.

Effect of crystalline admixture, fly ash, and PVA fiber on self-healing capacity of concrete

The ability of concrete admixtures to self-heal is an important way to improve concrete durability. The influence of crystalline admixture (CA), fly ash (FA) and PVA fiber on the self-healing capacity of early-age cracks in concrete was studied. The compressive strength recovery, electrical resistivity recovery, and morphology of crack surfaces were used to evaluate of early-age cracking in concrete. In this research four mixes are cast, control mix (M1), 0.1% of PVA fiber by volume mix (M2), 20% partial replacement of cement with fly ash mix (M3) and 2% of CA by mass of cement mix (M4). The cracks were formed by applying the compressive load for early-age cracks after 3 days of curing. Self-healing products are studied using scanning electron microscopy (SEM). It was observed that all admixtures show self-healing capacity to some extent. The results showed that the recovery of compressive strength and electrical resistivity of the cracked CA concrete samples has the highest self-healing capability due to the presence of calcium carbonate and C-S-H gel which were confirmed by SEM analysis.

Recovery of electrical resistivity, short-range order formation and migration of defects in electron-irradiated Fe–4Cr alloy doped with carbon

Resistivity recovery (RR) data of Cr4 alloy doped with carbon (Cr4C) after irradiation with 5 MeV electrons are presented and compared with RR data of non-doped Cr4 alloy. Analysis of the defect- and short-range order-induced parts of RR has confirmed the proposed earlier scheme of the evolution of Frenkel pair defects on post-irradiation anneal in Cr4 and Cr9. Vacancies start free migration around 205–210 K; however, the related peak of stage III is invisible in conventional RR plots. Interstitials atoms (IAs) trapped in stage I at configurations of several Cr atoms start their long-range migration at 220 K. Migrating vacancies are captured by carbon atoms in Cr4C while IAs are not. Dissociation of vacancies from carbon atoms at 350 K gives rise to a decoration of carbon atoms with Cr atoms. Indications are seen that a release of vacancies captured by atoms of residual nitrogen takes place around 250–260 K.

Difference approach to the analysis of resistivity recovery data for irradiated short-range ordered alloys

Electrical resistivity recovery (RR) data for irradiated concentrated alloys typically consist of two inseparable parts, one resulting from defect annihilation and the other from short-range order (SRO) effects. These parts exhibit different behaviour and often follow opposite trends. Therefore, in this case, analysis of RR data within the conventional method is too complicated. A new approach to data analysis of such a two-component RR is proposed. The approach involves a new quantity, the difference RR (DRR), which is composed of RR dependences of two similar samples irradiated to different defect concentrations. It is shown that the SRO formation proper and the stages corresponding to the onset of long-range migration of Frenkel pair defects, formed in each part of RR, can be clearly related to certain features of the DRR plots. This interrelationship allows detecting and identifying these stages in each part of RR separately. The validity of the approach is illustrated by analysis of the available pairwise RR data for Fe–16Cr–20Ni and Fe–4Cr alloys. It makes it possible to detect the small contribution from the SRO formation to RR in Fe–4Cr, which we failed to observe previously. It is shown that stage III of Fe–4Cr, which has a negligible contribution to the part of RR induced by defect annihilation, is clearly observed in the part induced by SRO formation.

Recovery of electrical-resistivity and viscoelasticity relaxation in thermally aged bulk Pd40Cu30Ni10P20 metallic glass

The structural relaxation of a bulk Pd40Cu30Ni10P20 metallic glass is studied by measuring the electrical resistivity and infralow-frequency (0.05 Hz) internal friction. It is demonstrated that the structural relaxation in thermally aged samples can be restored by quenching them from a supercooled liquid state. It is found that the degree of relaxation after quenching can exceed the initial one by several times.

First principles calculations in iron: structure and mobility of defect clusters and defect complexes for kinetic modelling

Predictive simulations of the defect population evolution in materials under or after irradiation can be performed in a multi-scale approach, where the atomistic properties of defects are determined by electronic structure calculations based on the Density Functional Theory and used as input for kinetic simulations covering macroscopic time and length scales. Recent advances obtained in iron are presented. The determination of the 3D migration of self-interstitial atoms instead of a fast one-dimensional glide induced an overall revision of the widely accepted picture of radiation damage predicted by previously existing empirical potentials. A coupled ab initio and mesoscopic kinetic Monte Carlo simulation provided strong evidence to clarify controversial interpretations of electrical resistivity recovery experiments concerning the mobility of vacancies, self-interstitial atoms, and their clusters. The results on the dissolution and migration properties of helium in α-Fe were used to parameterize Rate Theory models and new inter-atomic potentials, which improved the understanding of fusion reactor materials behavior. Finally, the effects of carbon, present in all steels as the principal hardening element, are also shown. To cite this article: C.C. Fu, F. Willaime, C. R. Physique 9 (2008).

Electrical resistivity and strain recovery studies on the effect of thermal cycling under constant stress on R-phase in NiTi shape memory alloy

In this paper, the results of electrical resistivity and strain recovery measurements involved in the study of the stability of R-phase in NiTi shape memory alloy upon thermal cycling under a constant tensile stress of 100 and 200 MPa are presented. Two wire samples are chosen such that the one heat-treated at 560°C exhibits a pure martensitic phase and the other heat-treated at 380°C consists of a mixture of R-phase and martensitic phase with residual austenites at ambient temperature. In both cases, the applied stress has been found to promote the R→A transformation during the heating part of the thermal cycling unlike the case of stress free condition in which R-phase is found to exist only in the cooling part of thermal cycling. R-phase is found to become more prominent with increasing applied stress. It is also found that the applied tensile stress enables the development of R-phase in the cooling part of the first thermal cycle itself in the sample heat-treated at 560°C whereas under stress-free condition it requires about 15 thermal cycles to develop R-phase. The NiTi wire heat-treated at 560°C exhibits more recoverable strain in the initial cycles than the wire heat-treated at 380°C, but after a large number of thermal cycles of the order of 1000 the recoverable strain in both samples is found to be almost the same. Under tensile stress, the sample heat-treated at 380°C is found to be more stable against plastic deformation with thermal cycling and hence can be preferred over the sample heat-treated at 560°C for two-way applications of SMA.

Recovery of electrical resistivity of high-purity iron irradiated with 30 MeV electrons at 77 K

The characteristics of radiation-induced defects in high-purity iron subject to 30 MeV electron irradiation at 77 K have been studied using electrical resistivity recovery measurements. For lowest electron dose, the stage II consists of two substages at 165 K and at 180 K. With increasing dose, the 165 K stage remains unshifted whereas the 180 K stage shifts to lower temperatures. These substages are attributed to the free migration of di-interstitials within and outside the displacement cascade, respectively. For higher electron doses, a slight substage (180–190 K) may be associated with the correlated annihilation of vacancies observed after fast neutron irradiation. Furthermore, another marked stage (210–240 K) with the dose dependence of peak temperature shift is ascribed to the monovacancy migration. From these results, it has been verified that the radiation damage produced by 30 MeV electrons comprises two types of defect structures; one associated with displacement cascades and the other one associated with simple displacement processes.

Interaction of solutes with irradiation-induced defects of electron-irradiated dilute iron alloys

Electrical resistivity recovery spectra were measured between 77 and 200 K on Fe and Fe dilute alloys (Fe–Mo, Fe–Cr, Fe–Si, Fe–P, Fe–Be) irradiated with 2.5 MeV electrons at 77 K in order to study the interaction of substitutional solutes with self-interstitials. Oversized Mo and undersized Si solutes annihilated the recovery stage I E in pure Fe, whereas slightly oversized Cr, and undersized P and Be solutes yielded new recovery stages below I E, the positions of which stages shifted toward lower temperatures with increasing solute concentration. These stages are most likely ascribed to the migration and annihilation of mixed-dumbbells formed for the most part in stage I D. The characteristics of these recovery spectra have not been observed in FCC alloys, which leads to the indication that the mixed-dumbbell in these alloys has a higher mobility than the self-interstitial.

Influence of nickel concentration on point defect migration in high-nickel Fe-Cr-Ni alloys

Point defect migration enthalpies were determined in high-nickel Fe-Cr-Ni alloys by studying electrical resistivity recovery in low-temperature irradiated fcc ternary alloys (16 wt.% Cr, 45 and 75 wt.% Ni). The results, together with previously obtained data, show that the mobility of self-interstitial defects increases progressively for higher nickel alloys. By contrast, vacancy migration is insensitive to composition in the range 20–45 wt.% Ni; a higher migration enthalpy value is observed for 75 wt.% Ni. The comparison with self-diffusion measurements shows that vacancy-formation enthalpy tends to decrease for increasing nickel contents.

Stage IV recovery in deformed tungsten

The recovery of electrical resistivity after heavy deformation has been investigated in tungsten of commercial purity. Parallel microstructural and resistometric studies have revealed that recovery stage IV of the heavily deformed tungsten can at least be partly ascribed to the anihilation of the extrinsic grain boundary dislocations (EGBDs). This recovery process precedes homogeneous grain growth and may be called grain boundary recrystallization.

Electrical resistivity recovery in Fe-Cr-Ni alloys after neutron irradiation at low temperature

Isochronal and isothermal annealing processes of austenitic Fe-Cr-Ni alloys and Type 316 steel are studied by electrical resistivity after fast neutron irradiation up to 2.9 × 10 21 n/m 2 at 5 K and after quench from 1473 K. Little resistivity change is observed below 80 K in the irradiated specimens and below 280 K in the quenched ones. The resistivity variation of the annealing curves in the irradiated specimens is formed by the resistivity decrease due to defect annihilation and the resistivity increase due to structural change produced by the self-interstitial and vacancy migration. Self-interstitials and vacancies migrate above 100 K and 300 K, respectively. The radiation-induced reesistivity consists of two contributions; the resistivity increase due to defect formation and the resistivity decrease due to disordering of solute atoms by cascade collision during neutron irradiation.

Recovery of electrical resistivity in ni alloys after neutron irradiation at low temperature

Abstract The isochronal annealing curves of the electrical resistivity in dilute Ni alloys have been measured after fast neutron irradiation at about 5 K. The suppression of the stage I recovery in dilute alloys is due to the trapping of interstitials at solute atoms. The trapping ability of interstitials in Ni alloys is very small as compared with that in Cu alloys. The substages in the stage II recovery are discussed in relation to the release of interstitials from solute atoms. In some concentrated alloys the retention of defects after annealing at 400 K is smaller than that in dilute alloys and pure Ni.

Mechanical properties of fast neutron irradiated zinc at 77K

Pure zinc single crystals were irradiated at liquid nitrogen temperature in the RA-1 reactor of CNEA up to fast neutron doses of 3 × 10 21 nm −2. Their plastic and fracture behaviour were studied at 77 K. Radiation hardening in zinc and copper was compared. It seems to be produced by the presence of similar irradiation-produced barriers to dislocation in both metals. For neutron doses greater than 4.5 × 10 20 nm −2 the ductility in crystals with easy glide orientations decreases rapidly by more than an order of magnitude. Fracture stress increased with dose, and it is dependent on crystallographic orientation. This fact shows that dislocation motion is necessary before fracture. Yield stress annealing experiments showed three important recovery stages located around 110, 160 and 210 K. The last stage, which is the most pronounced one, is hardly seen by electrical resistivity recovery.

Recovery of electrical resistivity in amorphous pdsi alloys after low temperature neutron irradiation

Abstract Measurements of electrical resistivity after low temperature fast neutron irradiation are made for amorphous Pd80Si20 and Pd80Ni2Sl18 and then Pd80Si20 annealed at 230°C and 360°C, and the isochronal annealing curves are obtained. The resistivity increase of Pd80Si20 annealed at 360°C is about 10 times larger than that of amorphous alloys and no defined annealing stage is observed in amorphous alloys and Pd80Si20 annealed at 360°C. For amorphous Pd80Si20, about 60% of the resistivity increase by irradiation remains after annealing up to room temperature and these are discussed by the structural relaxation.

Recovery of electrical resistivity and hardness in quenched β-brass

Abstract The recovery of electrical resistivity and hardness in quenched β-brass had been studied by isochronal annealing in the temperature range 25–500°C. Three stages of recovery were identified, with activation energies of 15 000, 31 000 and 36 680 cal mol−1 respectively. These results are attributed to migration of the disordered zinc atoms to vacant lattice sites, re-orientation of copper atoms and diffusion of zinc atoms in the matrix, respectively.

Isothermal Recovery of Electrical Resistivity in Aluminum Immediately after Deformation

Isothermal recovery curves of the electrical resistivity in deformed aluminum (99.995 at.% purity) were measured immediately after elongation. Specimens were elongated by about 4, 7 and 13%. A peak indicating the reverse recovery of resistivity was observed at adequate aging temperatures except for about 4% elongation. Experimental data were analyzed using the rate equation, where the clusters smaller than quadrivacancy were taken into account. The correspondence of the experimental results with the calculated ones is briefly discussed.