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This work evaluates the effectiveness of using forward creep deformation laws to predict the observed relaxation behaviour of 316H austenitic stainless steel. A summary of empirical creep methods, forward and stress relaxation experimental data were given. A primary and secondary creep strain rate (RCC-MR) model and an average creep strain rate model are combined with derived material constants to predict a group of stress relaxation tests at temperatures from 475 °C to 600 °C. The RCC-MR primary creep model predicted the stress relaxation behaviour soundly and the average creep strain rate model underestimated all of the stress relaxation data. The difference between stress relaxations predicted using strain hardening and time hardening versions of the RCC-MR equations are small. Factors affecting the predictions; including limitations in data range, data scatter, selection of a forward creep model, application of a forward model to stress relaxation and difference between forward creep and stress relaxation and are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The effect of H isotope exchange and radiation damage on the retention of D in W was examined in the PISCES linear plasma device. W samples were treated with D plasma at low sample temperatures (473K), with a fluence of 1026 ions/m2 and ion energies of 150eV. Each sample was then exposed to varying doses of H plasma with similar sample temperature and plasma conditions to fluences ranging from 0 to 1026 ions/m2, to examine the effectiveness of isotope exchange as a means of tritium removal. The D(3He, p)4He nuclear reaction was used to measure D concentration profiles up to a depth of 7.7μm. Thermal desorption spectroscopy (TDS) was used to determine the D retained throughout the bulk of the sample. Isotope exchange allows for a unique study of atomic migration by separately examining the diffusion of implanted atoms from those bombarding the surface. D atoms are exchanged out of traps as a result of H plasma bombardment and diffuse until either falling into another trap or reaching the surface to recombine and escape. Radiation damage at levels of 0.01, 0.1, and 1 displacements per atom (dpa) was carried out before plasma exposure on some samples with 2MeV Cu ions as a surrogate for damage caused by fusion neutrons. The Cu ion damage was compared to damage induced by 6MeVW ions to see if there is an effect of Cu contamination on retention. We saw little difference in Cu versus W ion damage at low dpa, but at 1dpa, where Cu content reached 65appm, contamination seems to be significant. Retention measurements showed that ion damage has little effectiveness on isotope removal at these sample temperatures; however, there is evidence to suggest that the trapping mechanisms in W change as damage is increased. [Copyright &y& Elsevier]

Abstract: The effect of sigma phase on the mechanical and wear properties of a Z3CN20.09M cast duplex stainless steel (CDSS) used in primary coolant pipe of nuclear power plants has been investigated. The experimental results showed that the sigma phase precipitated from ferrite at a temperature range of 600–900°C. The tensile and yield strengths of the specimens aged at 700°C decreased first and then increased with the increase of aging time. With increasing aging time, the impact energy of specimens decreased slightly before 4h and then dropped drastically when aged a longer time more than 10h. Fracture surface analysis showed that the hard and brittle sigma phase degraded the toughness of the aged steel. The hardness and wear resistance of the specimens aged for 1–4h were lower than those of un-aged ones. However, the higher values of hardness and wear resistance were got in the specimens aged more than 10h. [Copyright &y& Elsevier]

Abstract: In this study, 200keV Ne+ ion irradiations were performed under cryogenic conditions (∼77K) on δ-phase oxide compounds with formula, A4Zr3O12 (A=Sc, Lu and Dy). An order-to-disorder (O–D) phase transformation was observed in δ-Lu4Zr3O12 and δ-Sc4Zr3O12 after Ne+ ion irradiation, but no phase change was observed in Dy4Zr3O12. The latter compound exhibited a disordered fluorite structure before and after irradiation. The threshold doses to produce O–D phase transformations using Ne+ ions were found to be significantly lower than for similar irradiations (reported previously) using Kr++ ions. This suggests that light ions are more efficient than heavy ions in producing the retained defects that are ultimately responsible for the observed O–D transformation. The ion irradiation-induced O–D transformations observed here are discussed in terms of analogous transformations found in temperature–composition (T–C) phase diagrams for A4Zr3O12 compounds. [Copyright &y& Elsevier]

Abstract: Al2O3 fiber (Al2O3f) and SiC particle (SiCp) hybrid metal matrix composites (MMCs) were manufactured in a squeeze casting method and investigated for their mechanical and wear properties at elevated temperatures of 100°C and 150°C. The pin specimens had different ratios of fiber to particle content but their total weight fraction was constant at 20wt.%. Dry sliding wear tests were conducted with a pin-on-disk friction and wear tester. The morphologies of the worn surfaces were examined using a scanning electron microscope (SEM) to observe the wear characteristics and investigate the wear mechanism. An optical microscope (OM) was used to examine the precipitations of the MMCs after wear tests under different temperatures. The grown precipitations improved the hardness of the matrix material during the wear tests at 150°C. Thus, the wear resistance was enhanced at 150°C due to the precipitation strengthening of the FeSiAl5. Furthermore, the tests results revealed that the wear resistance of normal (N) MMCs was superior to that of planer random (PR) MMCs as the PR-fibers were easily pulled out whole from the worn surface. The results of this investigation showed that the wear resistance of dry sliding wear decreased as the SiCp content and increased at 100°C and 150°C, independently of the fiber orientation. [Copyright &y& Elsevier]

Abstract: This study investigates the room temperature sliding wear behaviors of Al2O3f and SiCp reinforced aluminum matrix hybrid composites under both the dry and lubricant conditions. The effects of fiber orientation of Al2O3f and hybrid ratio of Al2O3f volume fraction to SiCp volume fraction on the wear behaviors are discussed in details. The composite specimens with different fiber orientations and hybrid ratios were fabricated by squeeze casting method. The tests were carried out using a pin-on-disk friction and wear tester by sliding the pin specimens at a constant speed of 0.36m/s (570rpm) against a steel counter disk. The scanning electron microscope (SEM) images of the worn surfaces and debris were analyzed to understand the modes of wear. The results of dry sliding tests showed that the F20P0 unhybrid composites with normal (N)-orientation of fibers had better wear behaviors than those with planer-random (PR)-orientation of fibers. However, for hybrid composites, the wear behaviors were better for PR-orientation of fibers. On the contrary, the lubricant wear behaviors of F20P0 unhybrid composites with PR-orientation of fibers were superior to those with N-orientation of fibers while the hybrid composites exhibited the reverse lubricant wear behaviors. [Copyright &y& Elsevier]

Abstract: A pack cementation process was developed to coat commercial 9% Cr ferritic–martensitic steel T91 at temperatures below its normal tempering temperature to avoid any potential detrimental effect on the mechanical properties of the coated alloy. In order to prevent the formation of Fe2Al5 coatings, the Al activity in the pack cementation process was reduced by substituting the pure Al masteralloy with binary Cr–Al masteralloys containing either 15 or 25wt.% Al. When the Cr–25Al masteralloy was used, a duplex coating was formed at 700°C, consisting of a thin Fe2Al5 outer layer and an inner layer of FeAl. With the Cr–15Al masteralloy, an FeAl coating of ~12μm thick was achieved at 700°C. The pack aluminide coatings fabricated at 700°C are being evaluated in air+10vol.% H2O at 650°C and 700°C to determine their long-term oxidation performance. [Copyright &y& Elsevier]

The role of misfit stress in kinematic hardening under reversed straining of a Type 316H austenitic stainless steel has been investigated by using neutron diffraction combined with in situ deformation. Initial misfit stresses, often referred to an intergranular internal stresses, were created by the tensile pre-straining at high temperature. The misfit stresses at the length-scale of grain families, measured by neutron diffraction, were shown to be a function of the magnitude of the tensile pre-strain. The pre-strained specimens were further subjected to either continued (tensile) straining or reversed (compressive) straining at room temperature. In situ neutron diffraction measurements were undertaken to monitor the change of the misfit stresses during loading. The macroscopic stress–strain behaviour was used to derive isotropic and kinematic hardening stresses developed in the pre-strained specimens. Results show that the change of the transient softening stress towards a zero value is accompanied by a decrease in the change of the misfit stresses. A multi-scale self-consistent model has been developed to assist in understanding the measured change of the misfit stresses when subjecting the material to strain reversal. An important conclusion is that the origin of the kinematic hardening of Type 316H austenitic stainless steel arises from the misfit stress between grains. [ABSTRACT FROM AUTHOR]

Abstract: In this report, we present dramatically different behavior between isostructural Gd2Hf2O7 and Gd2Ti2O7 pyrochlore using 400keV Ne2+ irradiation under cryogenic conditions (∼77K), in which the lattice volume of the irradiated layer of Gd2Ti2O7 increased with ion fluence up to 1×1015 ions/cm2, whereas, the lattice volume of the irradiated layer of Gd2Hf2O7 decreased with increasing fluence from 1×1015 to 6×1016 ions/cm2. The cation radius ratio r A/r B, the bond-type of A–O and B–O bonds, the order-to-disorder transition energy of Gd2Hf2O7 and Gd2Ti2O7, temperature–composition (T–C) phase diagrams of HfO2–Gd2O3 and TiO2–Gd2O3 mixtures were used to explain the response of Gd2Hf2O7 and Gd2Ti2O7 to ion irradiation-induced structure transformation. [Copyright &y& Elsevier]

Metal hydride (MH) material can be used for effective separation of hydrogen from gas mixture. However, some impurities in the feedstock gas may cause the poisoning of the material and hence failure of the MH-based hydrogen separation system. In this paper, the hydrogen storage alloy LaNi 4.3 Al 0.7 , which has low-plateau pressure and was supposed to be used for hydrogen separation from the semi-coke oven gas, was tested in the atmosphere with relatively high concentration of CO impurities (∼0.1%v/v) by cycling experiments. Interestingly, the hydrogen storage capacity of the material shows quite mild decline during contact with CO at the temperature of 363 K or higher, and relatively fast kinetics can be kept, highlighting its application potential for hydrogen separation on a variety of occasions. [ABSTRACT FROM AUTHOR]

A potentially enhanced radiation resistance of nanocrystalline materials, as a consequence of the high density of interfaces and surfaces, has attracted much attention both to understand the fundamental role of these defect sinks and to develop them for high-radiation environments. Here, irradiation response of nanocrystalline A 2 Ti 2 O 7 (A = Gd, Ho and Lu) pyrochlore powders with grain sizes of 20–30 nm was investigated by 1-MeV Kr 2+ ion bombardment. In situ transmission electron microscopy (TEM) revealed that the critical amorphization fluence for each nanocrystalline compound at room temperature was greater than that for their coarse-grained counterparts, indicating an enhanced amorphization resistance. The effect of temperature on the irradiation response of one of these compounds, nanocrystalline Lu 2 Ti 2 O 7 , was further examined by performing ion irradiation at an elevated temperature range of 480–600 K. The critical amorphization temperature ( T c ) was found to be noticeably higher in nanocrystalline Lu 2 Ti 2 O 7 (610 K) than its coarse-grained counterpart (480 K), revealing that nanocrystalline Lu 2 Ti 2 O 7 is less resistant to amorphization compared to its coarse-grained phase under high temperatures. We interpret these results with the aid of atomistic simulations. Molecular statics calculations find that cation antisite defects are less energetically costly to form near surfaces than in the bulk, suggesting that the nanocrystalline form of these materials is generally less susceptible to amorphization than coarse-grained counterparts at low temperatures where defect kinetics are negligible. In contrast, at high temperatures, the annealing efficiency of antisite defects by cation interstitials is significantly reduced due to the sink properties of the surfaces in the nanocrystalline pyrochlore, which contributes to the observed higher amorphization temperature in the nano-grained phase than in coarse-grained counterpart. Together, these results provide new insight into the behavior of nanocrystalline materials under irradiation. [ABSTRACT FROM AUTHOR]

A Nd 3+ doped LaF 3 crystal has been grown by Czochralski method, and the X-ray diffraction results show that Nd 3+ have not changed the essential LaF 3 structure. Room temperature absorption spectrum, fluorescence spectrum and fluorescence decay curve of the crystal are measured and analyzed in detail. By applying the Judd–Ofelt approach, the emission probabilities, branching ratios and radiative lifetime for the transitions from 4 F 3/2 manifold are investigated. Furthermore, the emission cross-section for the transition of 4 F 3/2 → 4 I 11/2 as well as the fluorescence lifetime of 4 F 3/2 manifold are obtained and analyzed. The radiative lifetime, fluorescence lifetime and quantum efficiency are 567 μs, 522 μs and 92%, respectively. The results are compared with other Nd 3+ doped hosts, indicating that Nd:LaF 3 is favorable laser media. [ABSTRACT FROM AUTHOR]

Abstract: Radiation damage mechanisms in single crystal SrTiO3 irradiated with 250keV Ne ions to a fluence of 1.11×1020 ions/m2 at both room temperature and 773K were systematically investigated. The irradiation-induced microstructural evolution was characterized using transmission electron microscopy. Ion irradiation at room temperature results in amorphization of crystalline SrTiO3 near the peak damage region at this fluence. On the other hand, ion irradiation at high temperature leads to less irradiation-induced damage in SrTiO3 due to the higher recovery rate of defects. Nevertheless, the formation of dislocation loops has been observed in the SrTiO3 crystals irradiated at high temperature. These dislocation loops were determined to be unfaulted loops with Burgers vector along 〈011〉. [Copyright &y& Elsevier]

Abstract: We compare the evolution of microstructure and mechanical properties of Ag/Ni multilayers of varying layer thickness (1–200nm) subjected to helium ion and proton irradiation at room temperature to similar dose, ∼2 displacements-per-atom on average. Layer structure remained intact after both types of irradiation although defects accumulated in the layers are different. Helium bubbles were the major defects in helium ion irradiated films, while dislocation loops were ubiquitous in proton irradiated multilayers. In He ion irradiated multilayers, radiation hardening was greater than that in proton irradiated specimens, and the magnitude of hardening decreased with decreasing individual layer thickness. In comparison no size dependent hardening was observed in proton irradiated films. Mechanisms of irradiation induced hardening were discussed. [Copyright &y& Elsevier]

Abstract: The dependence of the width of void-denuded zones (VDZs) on grain boundary (GB) characters was investigated in Cu irradiated with He ions at elevated temperature. Dislocation loops and voids formed near GBs during irradiation were characterized by transmission electron microscopy, and GB misorientations and normal planes were determined by electron back-scatter diffraction. The VDZ widths at Σ3〈110〉 tilt GBs ranged from 0 to 24nm and increased with the GB plane inclination angle. For non-Σ3 GBs, VDZ widths ranged from 40 to 70nm and generally increased with misorientation angle. Nevertheless, there is considerable scatter about this general trend, indicating that the remaining crystallographic parameters also play a role in determining the sink efficiencies of these GBs. In addition, the VDZ widths at two sides of a GB show different values for certain asymmetrical GBs. Voids were also observed within GB planes and their density and radius also appeared to depend on GB character. We conclude that GB sink efficiencies depend on the overall GB character, including both misorientation and GB plane orientation. [Copyright &y& Elsevier]

Abstract: Epitaxial anatase films with thickness of around 300nm were deposited on and irradiated with 250keV Ne ions at room temperature. X-ray diffraction, Rutherford backscattering spectrometry, and transmission electron microscopy were used to characterize the microstructural changes under irradiation. Two primary features are observed in the irradiated material: a damaged layer with a high density of nano-sized defects including dislocation loops was observed in the film and, near the interface, a defect denuded zone formed on the side while an amorphous layer formed on the side. Atomistic calculations attribute the formation of both the defect-denuded zone and the interfacial amorphous layer not to the interaction between the irradiation induced defects and the hetero-interface but rather differences in chemical potential and mobilities for defects in each of the two phases. [Copyright &y& Elsevier]

Abstract: A study of the effects of ion irradiation of organically modified silicate thin films on the loss of hydrogen and increase in hardness is presented. NaOH catalyzed SiNa w O x C y H z thin films were synthesized by sol–gel processing from tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto Si substrates. After drying at 300°C, the films were irradiated with 125keV H+ or 250keVN2+ at fluences ranging from 1×1014 to 2.5×1016 ions/cm2. Elastic Recoil Detection (ERD) was used to investigate resulting hydrogen concentration as a function of ion fluence and irradiating species. Nanoindentation was used to measure the hardness of the irradiated films. FT-IR spectroscopy was also used to examine resulting changes in chemical bonding. The resulting hydrogen loss and increase in hardness are compared to similarly processed acid catalyzed silicate thin films. [Copyright &y& Elsevier]