Low-temperature Plastic Deformation Research Articles

Feasibility Analysis of Resource Application of Dry Flue Gas Desulfurization Ash in Asphalt Pavement Materials

To verify the feasibility of applying dry flue gas desulfurization ash (DFGDA) to asphalt pavement materials, the asphalt mastic (filler and asphalt composition) prepared by adding different proportions of DFGDA and LSP (limestone powder) into 70# matrix asphalt was studied experimentally. The asphalt mastics were subjected to the penetration test, the softening point test, and the ductility test. Moreover, the rheological properties of asphalt mastic were evaluated with dynamic shear rheometer (DSR) tests and bending beam rheometer (BBR) tests. An interaction ability index C-value based on the Palierne model was proposed to evaluate the interaction ability between DFGDA and asphalt. The influence of DFGDA asphalt on the interaction ability of matrix asphalt was observed and evaluated using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results showed that with the increasing proportion of DFGDA, the penetration of asphalt mastic gradually decreased, the softening point increased, and the ductility slightly decreased. At the same temperature, the dynamic shear modulus G* of the asphalt mortar significantly increased with increasing DFGDA content. The incorporation of DFGDA negatively affected the low-temperature plastic deformation resistance of asphalt, but the impact was weakened with the growing DFGDA amount and the powder mastic ratio. The combination mode of DFGDA and matrix asphalt depends on the physical blending, and their interaction ability mainly depends on the miscibility between DFGDA and matrix asphalt. In conclusion, DFGDA can be utilized as a novel filler in asphalt pavement materials.

Achieving high strength-ductility synergy in TiBw/near α-Ti composites by ultrafine grains and nanosilicides via low-temperature severe plastic deformation

The common problem of low strength-ductility matching prevails in near-α high-temperature titanium matrix composites (TMCs). In this work, the design strategy of ultrafine grains and dispersed (Ti, Zr)6Si3 nanoprecipitates in the microstructure of TiBw/near α-Ti composites via low-temperature isothermal multidirectional forging (IMDF), is expected to break the trade-off dilemma between strength and ductility. The results show that with the decrease in the temperature of IMDF, the grain scale decreased from 0.98 to 0.59 μm, and the location of silicide precipitation shifted from phase boundaries and grain boundaries to α-grain boundaries and intracrystalline regions. The experiments confirm that the local segregation of Si and the temperature of thermomechanical deformation are the key factors affecting the precipitation behavior of silicides. With the decrease of the deformation temperature, the precipitation mechanism of silicides changes from a single diffusion-controlled precipitation to the coupling of two mechanisms, namely, elemental diffusion and dislocation-assisted nucleation, which facilitates the successive precipitation of nanometer-sized silicides at the grain boundaries and in the inner regions. The ultimate tensile strength (UTS) and elongation of the composites were substantially increased after IMDF at 950 and 800 °C, especially the excellent performance at 800 °C, where the strength reached 1320.3 MPa and the elongation was 5.8 %. The room and high-temperature strengthening and failure mechanisms of the composites are analyzed and discussed, and the yield strength (YS) increments provided by various strengthening mechanisms at room temperature are quantified, aiming to provide a potential preparation strategy for the synergistic strengthening of near-α TMCs with ultrafine grains and nanoparticles.

Low-Temperature Elastic Properties of Molybdenum Doped Non-Equiatomic High Entropy Alloys of the Fe-Co-Ni-Cr System

The mechanical properties and microstructural evolution of a medium-entropy alloy Co17.5Cr12.5Fe55Ni10Mo5 (at%) in a low temperature range (including the record low temperatures region down to 0.5 K) were investigated. It has been established that low-temperature plastic deformation initiates martensitic phase transformations in this alloy, and the values of the dynamic modulus of elasticity correlate with the degree of phase transformations.

Effect of Low-Temperature Severe Plastic Deformation on the Saturation Magnetization and the Crystal Geometry Characteristics of the Phases in a Metastable Fe–18Cr–10Ni Alloy

Effect of Low-Temperature Severe Plastic Deformation on the Saturation Magnetization and the Crystal Geometry Characteristics of the Phases in a Metastable Fe–18Cr–10Ni Alloy

CO2‐Induced Modulation of Si–O Bonds for Low Temperature Plastic Deformation of Amorphous Silica Nanoparticles with Enhanced Photoluminescence

Modulation of Si–O bonds under mild conditions has been a challenging issue in the field of material science, which is critical to manufacture high‐performance silica‐based optical and photonic devices. Herein, we introduce a nondestructive technique to achieve Si–O bond rearrangement, leading to plastic deformation and photoluminescence enhancement of amorphous silica nanoparticles using supercritical carbon dioxides in EtOH/H2O solution under mild temperature. Specifically, plastic deformation is achieved by treating hollow mesoporous silica nanospheres using supercritical CO2 at 40 °C under 20 MPa. Experimental and theoretical studies revealed the critical role of supercritical CO2 in the plastic deformation process, which can be intercalated into the hollow mesoporous silica nanospheres with anisotropic stresses and induces the rearrangement of Si–O bonds and transformation of ring structures. This work suggests a novel approach to engineer high‐performance nano‐silica glass components for numerous optical and photonic devices under mild condition.

Discovery of multimechanisms of screw dislocation interaction in bcc iron from open-ended saddle point searches

Dislocation motion and interactions determine mechanical properties in body-centered cubic (bcc) metallic materials. However, studying mechanisms for the screw dislocation interaction is fundamentally challenging since many underlying processes involve mesotimescales and atomistic resolution, currently inaccessible by either experimental techniques or continuum theoretical methods. In this paper, we develop a computational capability based on self-evolving atomistic kinetic Monte Carlo (SEAKMC) to sample the critical events and saddle point energies related to screw dislocations and their junctions. The method is first validated by calculating the stress dependence of Peierls barriers and formation energies of kink pairs and cross-slip kink pairs on a single screw dislocation in bcc iron. Then the method is applied to a binary junction of a pair of intersecting screw dislocations, the structure of which is crucial for low-temperature plastic deformation. We identify three important mechanisms: coplanar cross-slipping, jog-pinning, and a previously unknown unzipping mechanism during the evolution of the binary junction. The mechanisms are then further validated using classical molecular dynamics simulations. The computational capability developed in this paper provides an effective tool to evaluate screw dislocation related thermally activated events in complex stress conditions. The mechanisms discovered in this paper provide critical insights into temperature dependence of the anomalous slip, a breakdown of the Schmidt law, during the plastic deformation in bcc iron and can be generalized to other bcc metals.

Twinning and antitwinning in body-centered cubic metals

Deformation twinning in body-centered cubic (BCC) metals occurs by shearing the crystal along {112} planes parallel to 〈111〉 directions. One of these directions (twinning shear) produces a twin, but it is often argued that the opposite sense of shearing (antitwinning shear) does not lead to twin formation. However, recent slip trace and orientational mapping analyses made on many BCC metals after low-temperature plastic deformation show clear evidence of fine misoriented lamellae along the traces of {112} planes sheared in the antitwinning sense. To resolve this controversy, we have utilized molecular statics simulations to determine the energy barriers for uniformly shearing all transition and alkali BCC metals in the twinning and antitwinning sense. The results of these simulations show that twins in transition BCC metals of the 5th and 6th groups can be produced on both types of {112} planes, irrespective of whether the shear is applied in the twinning or the antitwinning sense. However, this is not the case for α-Fe and the BCC structures of the alkali metals Li, Na, and K, where twins are likely to occur only on {112} planes sheared in the twinning sense. Furthermore, we have used TEM diffraction pattern analyses to investigate the characters of misoriented deformation lamellae in Nb and Cr compressed at 77 K, which were found along {112} planes sheared in the antitwinning sense. We demonstrate that these regions constitute regular twins. Similar studies on α-Fe compressed at 77 K prove that twinning in this material takes place exclusively on {112} planes sheared in the twinning sense.

Effect of cryo-rolling on mechanical properties and microstructure of pure copper

It is a challenging task to achieve high strength without any loss in its electrical conductivity in pure copper because commonly used strengthening mechanisms such as alloying, grain boundary strengthening, and dislocation, result in an increase in strength but simultaneously reduce its electrical conductivity. However, if strengthening is achieved by introducing twin boundaries, then the reduction in electrical conductivity is minimal. These twin boundaries can be introduced in pure copper by low-temperature plastic deformation. Thus, the main objectives of the present research work are to understand the evolution of the microstructure and the resulting mechanical property correlation during liquid nitrogen temperature (LNT) deformation and to compare it with room temperature (RT) deformation. For profile rolling analysis, copper is subjected to profile rolling at both RT and LNT rolling processes to a true strain of 1.77 with a step size of 0.11% strain. High-resolution electron backscatter diffraction coupled with orientation image mapping technique and transmission electron microscopy are used for microstructural characterization of the profile-rolled copper samples. The microstructural characterization reveals mechanical twins of 10–100 nm thickness in samples subjected to LNT, whereas there are no traces of mechanical twins in RT samples. The mechanical characterization by tensile test and hardness test shows that the samples deformed at LNT conditions have superior properties compared to RT.

Welding behavior of an ultrahigh-strength quenching and partitioning steel by fusion and solid-state welding methods

How the quenching and partitioning (Q&P) steel with an ultrahigh strength (>1 GPa) behaves during the welding process is a considerable issue for its practical application, but the systematical evaluation on the welding behavior of this new steel has not yet been concerned. Here the structure-property relationships of three typical Q&P 1180 steel joints were comparatively studied by using laser welding (LW), tungsten inert gas (TIG) welding, and friction stir welding (FSW). Weld metal (WM) region and heat-affected zone were generated in the welded joints and their widths were mainly related to the welding linear energy (LW < FSW < TIG welding). During LW and TIG welding, the parent metal (PM) was totally destroyed and coarsened in the WMs whereas ultrafine microstructures with high hardness were obtained after FSW by means of the low peak temperature and severe plastic deformation. The TIG welding produced serious material softening, while the softening degree could be alleviated via LW and FSW. Excellent tensile strength as high as that of the PM was achieved in both the LW and FSW joints by means of the suppressed material softening as well as small soft zone width. However, dramatic losses of strength and ductility were found in the TIG welded joint owing to the premature strain localization and fracture in the soft zone.

Heterogeneity in texture and crystal fabric of intensely hydrated ultramylonitic peridotites along a transform fault, Southwest Indian Ridge

Microstructures and olivine crystal fabrics were studied in amphibole-bearing peridotite samples obtained from the Marion Fracture Zone of the Southwest Indian Ridge by dredge D19 of the 1984 PROTEA Expedition Leg 5 cruise of the RV Melville. The peridotites show various textures ranging from extremely fine-grained well-layered ultramylonites to heterogeneously strained tectonites. Electron back-scatter diffraction analyses revealed that olivine crystal-preferred orientations (CPOs), which are developed primarily in coarse granular peridotites in the mantle, become weaker with an increasing degree of grain-size reduction from coarser to finer grains, for both porphyroclastic and matrix olivine grains. However, two well-layered ultramylonites are characterized by bimodal CPOs of (010)[001] (B type) and (001)[100] (E type) or a strong maximum of [010] normal to the foliation and girdle patterns of both [100] and [001] on the foliation plane (i.e., an axial [010] pattern or AG type). Moreover, spinel grains within these well-layered ultramylonites have not only been broken down to form olivine and amphibole by hydrous reactions, but have also been fractured and their fragments pulled apart in the fine-grained matrix. These features indicate that shear deformation occurred as increasing stress under hydrous conditions during the final stage of deformation, which enabled the local occurrence of low-temperature plastic deformation, resulting in the development of a CPO and a foliation within the ultramylonites.

Low-temperature degradation resistance and plastic deformation of ATZ ceramics stabilized by CaO

In this work, the phase composition (relative fractions of monoclinic m-ZrO2, tetragonal t-ZrO2, and cubic c-ZrO2 phases) and mechanical properties (hardness, fracture toughness, compressive strength) of alumina toughened zirconia (ATZ) ceramics, with an addition of silica were investigated. Calcium oxide was used as a stabilizer for the zirconia tetragonal phase. It was shown that CaO-ATZ+SiO2 ceramics demonstrate increased resistance to low-temperature degradation. The plasticity signs at room temperature were found due to the SiO2 addition to CaO-ATZ ceramics. A yield plateau appears in the uniaxial compression diagram at 5 mol. % SiO2 concentration. It is hypothesized that discovered plasticity is due to the increased t→m transformability.

Annealing behavior of aluminum after low-temperature severe plastic deformation

Severe plastic deformation (SPD) processes have received less attention at low temperatures (sub-zero and cryogenics). Hence, in this study, SPD of a commercially pure aluminum (AA1050) through Multi-Directional Forging (MDF) at Low-Temperature (LTMDF) and Room-Temperature (RTMDF) is investigated for different strains. Multi-directionally forged (MDFed) samples were annealed at 150, 250, 350, and 450 °C for 1 h, and some samples were stored at room temperature for periods up to 1 year. Results show that the hardness values and flow stress of LTMDFed aluminum are higher than those of RTMDFed ones. The ratio of yield strength to hardness for LTMDF is similar to that for RTMDF. Surprisingly, the work-hardening exponent of LTMDFed aluminum is higher than that of RTMDFed samples, which probably can be due to the increase in mobile dislocation fraction as a result of suppression of dynamic recovery. Microstructural evolutions, hardness, and flow stress changes of annealed samples indicate that LTMDFed samples are more affected than RTMDFed ones and have weak thermal stability because of the non-equilibrium microstructure. The study of self-annealing suggests a rather dramatic decrease in the hardness values of LTMDFed samples during a one-year period, which is not tangible for RTMDFed ones. LTMDF leads to grain coarsening during self-annealing, presumably owing to extended static recovery at room-temperature.

Enhancing Mechanical Properties of Mg–6Zn Alloy by Deformation-Induced Nanoprecipitation

We presented the solution of deformation-induced precipitation after homogenization to enhance the mechanical properties of Mg–6Zn alloys. The results show that the improved strategy exhibits more effective strengthening role than grain refinement methods based on low-temperature severe plastic deformation under the same strain. The low-temperature deformation with larger extrusion ratio results in massive nano-sized precipitates and excellent mechanical properties with the yield strength of 355 MPa and the ultimate tensile strength of 405 MPa. The increased mechanical properties are strong and tough enough to resist the stress and not be worn away when the alloy nail penetrates through the pig thigh bone, potentially extending more orthopedic surgery applications for Mg–Zn alloys.

General yield behaviors of the {1 1 0} hexagonal dislocation networks in body centered cubic metal molybdenum

The {110} hexagonal dislocation networks (HDNs) act as important carriers of the low-temperature plastic deformation in the body-centered-cubic (BCC) metals. Erenow, only a handful of studies have been performed on the yield behaviors of this planar networks, resulting in it being perplexing. In this letter, by three types of loading modes, the general yield behaviors, which comprise the critical stresses to move the network along any direction on the (011¯) plane, the partitions on the cooperative motion of two or three sets of dislocations and the conditions under which the steady motion of the HDN takes place, are proposed to disclose the motion mechanism for the HDNs in molybdenum by atomistic simulations. Also, the characteristic that the motion directions of the HDN are changeable, a result of the natural transition to the steady motion, explains why there is no fixed dead band for the (011¯) anomalous slip in these BCC metals.

Influence of the heat-treatment prior to plastic deformation on the aging behavior and the hardness of the aluminum alloy 6056

Motivated by the improvement of the cost and resource efficiency of the manufacturing process of age-hardening aluminum components, the influence of an initial heat-treatment, prior to plastic deformation, on the artificial aging behavior and the hardness is investigated. Systematic work is done by comparing three initial heat-treatment conditions of the age-hardening aluminum alloy 6056 prior to low-temperature plastic deformation: a solid-solution heat-treated, a naturally aged and a stabilized one. Two plastic deformation processes, linear extrusion and compression, each with two different strains, respectively, were performed and followed by artificial aging. The hardness was measured prior to plastic deformation as a function of the natural aging time, and after plastic deformation as a function of the artificial aging time. Stabilization annealing of the aluminum alloy inhibited natural aging. After plastic deformation and artificial aging, the stabilized conditions showed an increased hardness, as compared to the solid-solution heat-treated, respectively naturally aged, condition. The artificial aging behavior of all tested conditions was only slightly influenced by the respective plastic deformation process. However, the hardness was similar for the extruded, respectively compressed, conditions in their respective initial heat-treatment conditions.

Low-temperature severe plastic deformation of pure magnesium

Low-temperature severe plastic deformation of pure magnesium

High stresses stored in fault zones: example of the Nojima fault (Japan)

Abstract. During the last decade pulverized rocks have been described on outcrops along large active faults and attributed to damage related to a propagating seismic rupture front. Questions remain concerning the maximal lateral distance from the fault plane and maximal depth for dynamic damage to be imprinted in rocks. In order to document these questions, a representative core sample of granodiorite located 51.3 m from the Nojima fault (Japan) that was drilled after the Hyogo-ken Nanbu (Kobe) earthquake is studied by using electron backscattered diffraction (EBSD) and high-resolution X-ray Laue microdiffraction. Although located outside of the Nojima damage fault zone and macroscopically undeformed, the sample shows pervasive microfractures and local fragmentation. These features are attributed to the first stage of seismic activity along the Nojima fault characterized by laumontite as the main sealing mineral. EBSD mapping was used in order to characterize the crystallographic orientation and deformation microstructures in the sample, and X-ray microdiffraction was used to measure elastic strain and residual stresses on each point of the mapped quartz grain. Both methods give consistent results on the crystallographic orientation and show small and short wavelength misorientations associated with laumontite-sealed microfractures and alignments of tiny fluid inclusions. Deformation microstructures in quartz are symptomatic of the semi-brittle faulting regime, in which low-temperature brittle plastic deformation and stress-driven dissolution-deposition processes occur conjointly. This deformation occurred at a 3.7–11.1 km depth interval as indicated by the laumontite stability domain. Residual stresses are calculated from deviatoric elastic strain tensor measured using X-ray Laue microdiffraction using the Hooke's law. The modal value of the von Mises stress distribution is at 100 MPa and the mean at 141 MPa. Such stress values are comparable to the peak strength of a deformed granodiorite from the damage zone of the Nojima fault. This indicates that, although apparently and macroscopically undeformed, the sample is actually damaged. The homogeneously distributed microfracturing of quartz is the microscopically visible imprint of this damage and suggests that high stresses were stored in the whole sample and not only concentrated on some crystal defects. It is proposed that the high residual stresses are the sum of the stress fields associated with individual dislocations and dislocation microstructures. These stresses are interpreted to be originated from the dynamic damage related to the propagation of rupture fronts or seismic waves at a depth where confining pressure prevented pulverization. Actually, M6 to M7 earthquakes occurred during the Paleocene on the Nojima fault and are good candidates for inducing this dynamic damage. The high residual stresses and the deformation microstructures would have contributed to the widening of the damaged fault zone with additional large earthquakes occurring on the Nojima fault.

Change in Properties of Pipe Steel with Two-Phase Structure During Low-Temperature Heating and Subsequent Plastic Deformation

Results are given for evaluation of the effect of longitudinal deformation on the change of the mechanical properties and steel properties with a two-phase pipe metal structure previously given low-temperature heat treatment simulating application of an anticorrosion coating. A reduction in steel deformation capacity to the minimum permissible level is evaluated by a criterion δun ≥ 3% and σy(Rt0.5)/σu ≤ 0.96–0.98. As a result of testing plates subjected to longitudinal tension with plastic deformation ep = 1.5–7.0%, it is shown that exhaustion of steel deformation capacity is predicted in the transverse direction with preliminary deformation ep ≈ 5%, and in the longitudinal direction with ep ≈ 4–5%. SEM and TEM methods are used to study the effect of steel main structural characteristics whose presence facilitates retention of capacity for steel strain hardening after heating (200–220°C, 5 min): fine islands of twinned martensite, fine cementite particles and abundant precipitation of nanosize particles of Nb and V carbonitrides. During branch pipe bending deformation (ep ≤ 3.0%) in a two-phase steel structure (main components are ferrite and lath martensite) includes transformation of residual austenite from the MA-component in twinned martensite.

Phase evolution of highly immiscible alloys under shear deformation: Kinetic pathways, steady states, and the lever-rule

Phase evolution of dilute, highly immiscible, Cu alloys (Cu-Nb, Cu-V, and Cu-Ta) during low-temperature severe plastic deformation was investigated using large-scale molecular dynamics simulations. At low solute concentrations, each system maintained a FCC structure in steady state, but as the concentration was increased above a saturation limit (0.3 at.% for Ta, 1 at.% for Nb and 5 at.% for V), the system became two-phase, comprising co-existing FCC and amorphous phases. Unlike Cu-Nb and Cu-V, the amorphous phase in the Cu-Ta system showed strong solute partitioning. Increasing the solute concentration above a second phase boundary (8 at.% V, 9 at.% Nb, and 24 at.% Ta) led to complete amorphization. Throughout the two-phase region, the compositions of the FCC and amorphous phases remained nearly constant, thus following the lever rule. Initiating the systems either as a FCC homogeneous alloy, or with a BCC sphere embedded in a Cu matrix, had no effect on the steady state microstructure, implying uniqueness of the steady state under low-temperature shear deformation. Lastly, chemical order and phase partitioning in the amorphous Cu-Ta system under low-temperature shear is found remarkably similar to that in the equilibrium structure above the melting temperature.

Degradation of tungsten monoblock divertor under cyclic high heat flux loading

The degradation behavior of the ITER divertor under the cyclic high heat flux loading has been varied in the previous studies, which would be induced by the intrinsic difference in the thermo-mechanical properties of each pure W material. Therefore, the experimental characterization of the thermo-mechanical properties of the W materials and the numerical structural analysis using these data are necessary to clarify the degradation mechanism and the prediction of the fracture scenario and lifetime. In this study, the degradation behavior of the pure W monoblock divertor mockup during the cyclic high heat flux loading test at 20MW/m2 was evaluated and the macro-crack formation mechanism was discussed based on the structural analysis. The macro-crack formation of the divertor mockup in the present study could occur due to a complexed low temperature cleavage fracture accompanied by the plastic deformation under cyclic loading. The fatigue, especially the low temperature fatigue with plastic deformation, could be a mechanism factor for the macro-crack formation. However, further study considering the thermo-mechanical fatigue and the effect of the low temperature plastic deformation is necessary to quantitatively evaluate the macro-crack formation mechanism by the fatigue.