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Unusual physical properties associated with lattice defects induced by flash sintering and processing of oxide ceramics have attracted attentions. In this study, optical and mechanical properties of undoped and polycrystalline rutile TiO 2 subjected to alternating current (AC) flash processing were characterized through diffuse reflectance spectroscopy and nanoindentation experiments at room temperature. The flashed sample exhibited substantial optical blackening and elastic softening but negligible changes in the hardness and crystal structure. The elastic softening demonstrated a significant rate dependence (i.e., elastic moduli decreased with testing rate), which was possibly caused by stress-induced reordering of point defects induced by AC flash processing. This elastic softening suggests that pronounced ionic mobility is obtained by flash processing even in undoped systems, which can potentially be extended to a general understanding of mass transport phenomena in transient metal oxides in strong electric fields. [Display omitted] [ABSTRACT FROM AUTHOR]

The Snoek anelastic internal friction (IF) peak due to stress-induced dipole ordering associated with interstitial atoms was well observed in IF curves of single-principal element alloys (SPEAs) as early as in the 1950s, however, its behavior remains elusive in multi-principal element alloys (MPEAs) to date. Here the temperature-dependent IF spectra of NbTiV 0.5 Zr refractory MPEAs with varying O contents were presented, and the analysis of these data indicates that for O-doped NbTiV 0.5 Zr MPEAs, the O addition triggers two anelastic IF peaks (the P O1 and P O2), corresponding to the O-Snoek-type relaxation in random solid solution (RSS) and local chemical ordering (LCO) structures, respectively. The half-peak width of the P O1 is 2–3 times broader than that for SPEAs, associated with the wide O migration energy barrier distribution in MPEAs. These phenomena show a striking contrast to the single and narrow Snoek-type peak observed for SPEAs. Our analysis further reveals an approximate linear correlation between the half-peak width of the Snoek-type peak and the mixing entropy. The introduction of O also shifts grain boundary relaxation peaks (P G) towards higher temperatures. Interestingly, high-temperature anomalous modulus changes were observed for the first time in TiV-based lightweight refractory MPEAs, which is suggested to be originated from the order reduction of the body-centered cubic (bcc) structure at elevated temperatures. Moreover, the 1 at.%O doped NbTiV 0.5 Zr MPEA with a favorable balance between the peak heights of the P O2 and P G , exhibits outstanding specific yield stress (SYS) among refractory MPEAs while maintaining an elongation as high as 20 %. This work provides not only a bridge between the anelastic behavior of SPEAs and MPEAs for upcoming studies and theories concerning bcc MPEAs with interstitial atoms, but contributes to the holistic design of bcc MPEAs with high strength and excellent ductility. [Display omitted] [ABSTRACT FROM AUTHOR]

Potassium dihydrogen phosphate (KDP) crystals are widely used in high-power laser systems and inertial confinement fusion applications. However, machining KDP crystals using ultra-precision fly-cutting technology poses challenges due to the combined elastic, plastic, and brittle deformation mechanisms, making it difficult to analyze the material removal process. This investigation aims to observe and analyze the elastoplastic behavior of KDP crystals in the ductile region, which has received limited attention in previous studies. Nanoindentation experiments were conducted to analyze the elasto-plastic transition in KDP crystals, employing an approach instead of the traditional Oliver–Pharr method. Additionally, a cutting experimental method was developed to observe the reverse behavior during manufacturing by introducing a process with a 0 nm depth of cut. The results reveal significant rebound deformation and anelastic behavior, providing a comprehensive understanding of the deformation mechanism in KDP crystals at the nano- and micro-scale cutting levels. This knowledge contributes to modifying the diamond turning process and optimizing the fabrication procedure of KDP crystals. [ABSTRACT FROM AUTHOR]

The plastic anisotropy and unloading anelasticity of an extruded Mg-9 wt.%Al alloy (with two annealed textures) were investigated using in-situ neutron diffraction measurement and crystal plasticity modelling. The distinctive yielding and hardening behaviors during compressive and tensile loading-unloading cycles were interpreted by the alternative operations of different slip/twinning modes. We reveal that the micromechanical responses of differently-oriented grains strongly depend on their neighboring conditions and operative deformation mechanisms. Based on the modelling results, unloading anelasticity is hypothesized to be controlled by the plastic contribution of the hard deformation mode and its impeding effects on easier deformation modes. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Relaxation is a key feature in glassy physics, and the strain-induced effects on relaxations in metallic glasses are of practical significance, yet still unclear. Through a contrastive combination of dynamical mechanical spectroscopy and linear-heating stress relaxation methods, we find that strain effectively facilitates the relaxation dynamics with divergent modulation behaviors in a wide temperature range for metallic glasses. Two loading modes are coupled with linear-heating, and we experimentally confirm the “temperature-strain equivalence”. Our results benefit for better understanding the unique effect of strain on relaxation and for providing guidance on applications of metallic glasses with improved performances at different temperatures. [ABSTRACT FROM AUTHOR]

Zinc oxide tetrapods have remarkable functional and mechanical properties with potential applications in different fields including nanoelectronic and optoelectronic sensing, functional composites and coatings, as well as energy harvesting and storage. Based on the 3D shape of these microparticles, they can be assembled into highly porous (up to 98%) macroscopic ceramic framework structures that can be utilized as a versatile template for the fabrication of other multi-scaled foam-like materials. Here we investigated the three-dimensional structure of low density interconnected zinc oxide tetrapod networks by high resolution X-ray computed tomography. In situ observations during mechanical loading show inhomogeneous development of anelastic strain (damage) during compression, and homogeneous elastic recovery on unloading. Individual tetrapods are observed to deform by arm rotation to accommodate strain. [Display omitted] [ABSTRACT FROM AUTHOR]

The mechanism of anelastic behavior in “strain glass” alloy is juxtaposed between “strain glass freezing” and relaxational premartensitic anelasticity. We report here that hydrogen is an essential ingredient for the frequency-dependent internal friction peak around 160 K in Ti 50 Ni 44 Fe 6 alloy. This internal friction peak disappears in the de-hydrogenated Ti 50 Ni 44 Fe 6 alloy. It is proposed that the anelastic behavior of Ti 50 Ni 44 Fe 6 alloy results from the interaction between hydrogen and nanodomains. [ABSTRACT FROM AUTHOR]

Wrought magnesium alloys with low rare-earth (RE) contents are being considered for lightweight automotive applications. The purpose of this study was to identify the effect of strain ratio on cyclic deformation behavior of a rolled ZEK100-O Mg alloy with 0.2 wt% neodymium. The microstructure in its annealing condition consisted of equiaxed grains which were oriented with most c -axes perpendicular to the rolling direction. This alloy exhibited a superior combination of tensile strength and ductility due to its weak basal texture and decreased stacking fault energy. Significant plastic deformation occurred in the tensile phase of the first cycle at strain ratios of R ε =0 and 0.5. The asymmetry of initial hysteresis loops tended to diminish towards the mid-life cycles. With increasing strain ratio, fatigue life first increased, reached its maximum at a strain ratio of R ε =−1, and then decreased. This was attributed to a combined effect of mid-life stress amplitude, plastic strain amplitude and mean stress, where the stress amplitude increased and plastic strain amplitude decreased with increasing strain ratio. The closer the strain ratio to R ε =−1 was, the lower the absolute value of mean stress was. The mean stress relaxation occurred mainly in the initial stage and for the strain ratios more remotely from R ε =−1. The anelastic behavior of this alloy largely remained arising from the twinning and detwinning, with the strain ratio identified as an influential parameter via sensitivity analyses. The anelastic strain amplitude, along with three newly-defined parameters (eccentricity, angle deviation , and relative slope change) all decreased with increasing strain ratio, reflecting more symmetric hysteresis loops. [ABSTRACT FROM AUTHOR]

Low rare-earth (RE) containing magnesium alloys are being considered for the lightweight automotive applications to reduce fuel consumption and emissions. Design of magnesium components requires strain-controlled low-cycle fatigue (LCF) behavior. This study was aimed to evaluate the cyclic deformation characteristics and LCF life of a low (0.2 wt.%) Nd-containing ZEK100-O alloy. The alloy contained equiaxed grains along with some Mg 12 Nd particles, and exhibited a relatively weaker basal texture. While slight cyclic softening occurred at high strain amplitudes, cyclic stabilization remained at lower strain amplitudes. Fatigue life of ZEK100 alloy was longer than that of the extruded RE-free AZ31 and AM30 alloys, due to a fairly good combination of strength with ductility. The asymmetry and skewness of hysteresis loops, which were characterized by eccentricity, angle deviation, and relative slope change, respectively, were effectively improved relative to the extruded RE-free alloys, arising from less extensive twinning caused by texture weakening and grain refinement. While the pseudo-elastic behavior tended to decrease with RE addition, it largely remained. An additional term was thus introduced to calculate the total strain range, i.e., Δ ε t = Δ ε e + Δ ε p + Δ ε an , where the total anelastic strain range ( Δ ε an ) consisted of both tensile and compressive components. Fatigue crack initiated from the near-surface imperfections, and crack propagation was characterized by fatigue striation-like features. [ABSTRACT FROM AUTHOR]

Abstract: Cyclic tensile loading–unloading tests were carried out with a cyclically incremental strain of 0.03% in a strain range of 0–2% and with cyclically incremental strain of 1% till fracture to investigate the anelastic behavior of annealed Mg ZEK100 alloy sheet. Large hysteresis stress–strain loops were observed in all cyclic loading–unloading tests, which indicate that the annealed Mg ZEK100 alloy sheet exhibits obvious anelastic effect. Due to the fact that twins are easier to produce in transverse direction (TD) than in rolling direction (RD), the alloy shows larger hysteresis loops in TD when applying cyclic loading–unloading. Both true stress and true plastic strain have an effect on the anelastic effect. At a stress, ∼15MPa higher than the yield strength, the anelastic effect reaches the maximum and the hysteresis loops add an anelastic strain of 0.0018 in RD and 0.003 in TD to the total elastic strain, and consequently lead to a decrease of 30% and 54% in the apparent elastic modulus in RD and TD, respectively. This phenomenon is discussed in terms of the roles of partially reversible twinning and dislocation slip upon unloading and reloading. A novel phenomenological model is developed to describe the anelastic behavior in the Mg alloy, and the calculated hysteresis loops agree well with the experimental ones. Cyclic hardening in the alloy is observed after a certain number of cycles. [Copyright &y& Elsevier]

Effective models of the mechanical behavior of thermoelectric materials under device conditions require knowledge of temperature-dependent elastic properties. Between room temperature and 600 K, resonant ultrasound spectroscopy measurements of three skutterudite thermoelectric materials, i.e. n-type Co0.95Pd0.05Te0.05Sb3 (both with and without 0.1 at.% cerium dopant) and p-type Ce0.9Fe3.5Co0.5Sb12, showed that the Young's and shear moduli decreased linearly with temperature at a rate of −0.021 GPa/K to −0.032 GPa/K, and −0.011 GPa/K to −0.013 GPa/K, respectively. In contrast, the Poisson's ratio was approximately 0.22 for the three materials and was relatively insensitive to temperature. For temperatures >600 K, the elastic moduli decreased more rapidly and resonance peaks broadened, indicating the onset of viscoelastic behavior. The viscoelastic relaxation of the moduli was least for Ce-doped n-type material, for which grain boundary precipitates may inhibit grain boundary sliding which in turn has important implications concerning creep resistance. In addition, powder processing of the n- and p-type materials should be done cautiously since submicron-sized powders of both the n- and p-type powders were pyrophoric. [ABSTRACT FROM PUBLISHER]

Extreme anelastic responses (stiffness greater than diamond and large amplification of damping) due to the presence of a negative stiffness phase have been observed in Zn80Al20–BaTiO3 composites not only near the tetragonal–orthorhombic transformation temperatures of BaTiO3 anticipated by the classical Landau theory, but far below the Curie point of BaTiO3, which can be manipulated via specific aging processes that operate by an oxygen vacancy mechanism. The idea proposed herein can be utilized to fabricate novel composites for potential engineering applications. [ABSTRACT FROM AUTHOR]

Room-temperature uniaxial compression of Zr46.75Ti8.25Cu7.5Ni10Be27.5 bulk metallic glass at 80% of the yield stress leads to homogeneous viscous flow. The flow in this apparently elastic regime reveals large increases in volume associated with local shearing events in the glass. The extent of this dilatation is masked in more usual tests by significant relaxation of the glass structure during and after shear. The dilatation in deformed metallic glasses can no longer be attributed only to free-volume generation at shear bands. [ABSTRACT FROM AUTHOR]

Quantitative simulations of the carbon-induced internal friction in ferrite/martensite Fe-C and Fe-Ni-C alloys are performed by combining a mean-field elastic model and the atomistic kinetic Monte Carlo based on a pair interaction model to describe the composition-dependent carbon migration. The simulation is validated by experimental data and a thermo-kinetic theory. Our results predict that (i) additional peaks occur in the internal friction profiles of Fe-C and Fe-Ni-C due to C-C and Ni-C pair interactions; (ii) the Ni-alloying shifts the internal friction peak to lower temperature than in Fe-C alloys; (iii) the peak temperature is not simply related to the most frequent carbon jumps during the relaxation process; (iv) the internal friction behavior in martensite depends on the excitation direction with respect to the carbon ordering direction. • Dramatic Ni-C interaction effect on the internal friction profile. • Excitation direction-dependent carbon Snoek relaxation in martensite. • Connection between atomic mechanisms and phenomenological internal friction signals. [ABSTRACT FROM AUTHOR]

Non-elastic strain behavior was investigated in detail for several different zirconia ceramics (Y-TZP, Y-FSZ, Mg-PSZ and Ce-TZP), and a possible mechanism for anelasticity was discussed. Y2O3-doped zirconia ceramics (Y-TZP and Y-FSZ) exhibited a remarkable degree of anelastic strain, as does Mg-PSZ to a lesser extent. On the other hand, Ce-TZP hardly produced anelastic strain. These results suggest that the anelastic properties depend on the particular dopant additive, irrespective of the crystallographic phase. In Mg-PSZ, besides the anelastic strain, a time-dependent non-recoverable strain is produced under loading. This non-recoverable strain corresponds to the strain caused by a phase transformation. It is suggested that the anelastic properties could be significantly influenced by the level of oxygen vacancy in the matrix, and that the anelastic strain might be produced by a slight shift of ionic species. [Copyright &y& Elsevier]