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In this work, the compressive creep behaviors of hot-rolled pure Mg (0Y alloy) and various hot-rolled Mg-Y binary alloys (0.15Y, 1.5Y, 4.5Y, 7.5Y, and 10.5Y alloys) at 523 K were systematically studied under various applied stresses. These alloys all had an average grain size of ~100 μm. The loading directions were parallel to the rolling direction (RD), transverse direction (TD), and normal direction (ND). The creep behaviors were shown to exhibit an obvious dependence on the loading direction in the 0Y, 0.15Y, 1.5Y, and 4.5Y alloys. The creep resistance had a sequence of ND > TD ≥ RD in these alloys. The creep anisotropy of the alloys was caused by 〈a〉 dislocation cross-slipping from the basal plane to the prismatic plane and { $$ 10\bar{1}2 $$ } twinning dominating the creep along the RD and TD, while dislocation climb and pyramidal 〈c + a〉 slip prevailed along the ND. Compared to the 0Y, 0.15Y, and 1.5Y alloys, the more random basal texture in the 4.5Y alloy weakened the cross-slip and twinning along the RD and TD and triggered cross-slip along the ND, resulting in decreased creep anisotropy. For the 7.5Y and 10.5Y alloys, an approximate creep isotropy due to cross-slip and pyramidal 〈c + a〉 slip dominated the creep along all three loading directions. Moreover, compared to the 0Y alloy, the creep resistance was found to be slightly increased in the 0.15Y alloy and significantly increased with increasing the Y content above 1.5 wt pct, which can be attributed to solution strengthening and the promoted pyramidal 〈c + a〉 dislocations collaboratively increasing the creep resistance. The improved hindering effect on twinning also helped to increase the creep resistance along the RD and TD. In addition, dynamic precipitation strengthening assisted the increment of creep resistance in the 10.5Y alloy. Thus, the addition of concentrated Y in Mg alloys is a valid solution to eliminate the compressive creep anisotropy and simultaneously enhance the creep resistance.

A compressive pre-straining of 0.05 was applied to two Mg–2Y alloy sheets with different initial textures along their normal directions. Creep behaviors of these sheets before and after the pre-straining were investigated at 493 K under stresses ranging from 20 to 100 MPa. The influence of pre-straining on creep behaviors was then discussed. The results show that the effects of pre-straining on creep behaviors of the two sheets are quite different. A profound strengthening effect of this pre-straining is observed on the creep resistance of the extruded sheet with creep strain decreased by half and steady strain rate reduced by 75% at most. By contrast, for the rolled sheet, the improvement of creep resistance by the pre-straining is negligible. The difference lies in the number of anomalous twins introduced by the pre-straining. After the pre-straining, considerable {10–12} anomalous twins have been introduced in the extruded sheet with a random initial texture, compared to the rolled one. Dislocation movements during the creep can be impeded by the large amounts of twins in the pre-strained extruded sheets, resulting in the obvious improved creep resistance. Meanwhile, different predominant dislocation mechanisms are found along different creep directions. Since a more excellent impeding effect of the twins is obtained on cross-slip, better improvement of the creep resistance can be achieved along the TD than along the ED of the pre-strained extruded sheet.

Compressive creep anisotropic behaviors were observed for a hot-extruded Mg–3Al–1Zn alloy rod at 423 K. Heavy basal slip accelerated the creep rate along transverse and 45° directions. Inversely, strong interactions between high densities of prismatic dislocations and {10–12} twins enhanced the creep resistance along extrusion direction. Although twinning was reported to induce yield softening during uniaxial loading, it could be beneficial for creep resistance even applied stress over yield stress.

This work aims to provide a reliable reference and a low-cost strategy for overcoming the trade-off between stretch formability and heat resistance in Mg alloys. A dilute Mg-0.8 wt%Nd alloy sheet was prepared for this purpose, and hot compression was conducted in order to regulate the microstructure and texture. For comparison, the samples with and without hot compression were labeled as fine-grained (FG) and coarse-grained (CG) samples respectively, corresponding to the occurrence of dynamic recrystallization. Tensile creep tests were carried out at 473 K and Erichsen tests were conducted at room temperature. Both the CG and the FG samples had higher stretch formability and stronger creep resistance than commercial Mg alloys tested for comparison. Especially, the FG sample performed the best in overcoming the trade-off. Pyramidal slip dominated the creep behavior of the FG sample and enhanced the heat resistance, avoiding the deterioration caused by cross-slip, twinning and grain boundary sliding. High Schmid factors for basal slip of the fine grains enhanced the stretch formability of the FG sample, and compensated the adverse effect of the relatively low Schmid factors of the residual coarse grains. Thus, the dilute Mg-0.8 wt%Nd alloy successfully overcame the trade-off between stretch formability and heat resistance.

Creep stress including tensile loading and compressive loading was carried out on hot-rolled Mg-3wt%Gd alloy at 473 K along the rolling direction (RD) and the normal direction (ND) separately. For briefness, T-RD was applied to representing the sample under tensile creep loading along the RD. The other three samples were named C-RD, T-ND and C-ND, respectively. The results of creep tests showed an obvious tension-compression asymmetry along both the RD and the ND. Twinning deteriorated the creep resistance of the C-RD and the T-ND samples, and caused the resultant asymmetrical behavior. The T-RD sample had the best creep resistance, followed by the C-ND sample, and the last two samples with similarly poor creep resistance were the C-RD and the T-ND. During creep loading, the T-RD sample was controlled by cross-slip containing a-dislocations. The C-ND sample were dominated by basal slip and pyramidal slip. Both the C-RD and the T-ND samples were dominated by cross-slip and twinning. Furthermore, compared to the asymmetrical behavior along the RD, pyramidal slip in the C-ND sample weakened the asymmetrical behavior along the ND. However, basal slip deteriorated the creep resistance of the C-ND sample. Therefore, future researches for developing dilute Mg-RE based alloys with high creep resistance should be inducing pyramidal slip, inhibiting twinning and impairing basal slip.

In heat-resistant Mg Gd based alloys, the relationship between the collective effects of precipitate origin and precipitate-free zone (PFZ) development on the creep resistance is still unclear. In this work, a hot-rolled Mg-13wt%Gd binary alloy was treated by solid solution (SS sample) and peak aging (AA sample). After peak aging, static precipitated β′ phases were widely generated and PFZs were directly formed along both sides of the grain boundaries in AA sample. Tensile creep tests were performed at 523 K on both SS and AA samples. During creep testing, dynamic precipitated β′ phases were gradually generated in SS sample while the β′ phases persisted as large scales in AA sample. The dominant creep mechanisms of SS sample were twinning and cross-slip composed by dislocations, since the late occurrence and low density of β′ phases failed in hindering the movement dislocations at the beginning of steady creep stage. On the contrary, the large-scale β′ phases reduced the space for dislocation movement and succeeded in retarding cross-slip, leading to pyramidal slip being the main creep mechanism of AA sample. Besides, PFZs were formed in SS sample (from zero to ~1.1 μm) while they became narrower in AA sample (from ~5 μm to ~1.7 μm). The large decreased ratio of PFZ width, the large scale of static precipitated β′ phases and the resultant pyramidal slip effectively enhanced the creep resistance of AA sample. Accordingly, AA sample behaved a higher creep resistance in comparison to SS sample at 523 K. It is hoped that the roles of precipitate origin and PFZ development in the creep properties can enrich the theories and methods in improving the service performance of Mg Gd series at medium to high temperatures.

This study investigates the impacts of artificial aging state on the tensile creep resistance of a hot-rolled Mg-3.5 wt%Nd alloy. The alloy was heat treated under different conditions, including solution treatment at 490 °C, under-aging for 2, 5, and 10 h, and peak-aging for 20 h at 220 °C. The samples were abbreviated as AS, A2, A5, A10, and A20, respectively. After aging for 2 h, many precipitates appeared in the under-aged A2 sample, most of which were lenticular β ′ -phase precipitates. With an increasing aging duration, β ′ transitioned to β 1 and substantial solute depletion was observed. The A2 sample had no precipitate-free zone (PFZ), but PFZs formed in A5, widened in A10, and evolved into the widest in the peak-aged A20 sample. During creep testing at 250 °C, β 1 phases precipitated in the AS sample, and atomic diffusion induced the formation and widening of PFZs. Pyramidal dislocations and β 1 dissolution induced grain boundary migration and rapid PFZ widening in the A20 sample, which was less obvious in the A10 and A5 samples. The slightest solute depletion in the grain boundaries during artificial aging and the unconspicuous β 1 dissolution during creep testing avoided fast PFZ widening in the A2 sample. Consequently, although the A20 sample had the highest strength at room temperature, wide PFZs and grain boundary migration led to severe stress concentration and deteriorated its creep resistance. Narrow PFZs and dislocations cutting the β ′ phases in the A2 sample led to the best creep resistance.

Both static precipitation and dynamic precipitation could hardly enhance the creep resistance of dilute Mg-Nd alloys. To solve this problem, the present paper proposed a practical method, which was combining pre-compression and subsequent peak-aging. A binary Mg-1.5 wt%Nd alloy plate, was prepared for researching the tensile creep behaviors at 523 K. Due to the aging hardening was weak, the directly aged sample was not studied. The pre-compressed sample was named PC sample, and the pre-compressed with subsequent peak-aged sample was named PC-AA sample, while the sample without any pre-compression or aging was named NPC sample. The PC-AA sample had the best creep resistance, followed by the NPC sample, and the PC sample had the poorest. For the NPC sample, twinning and dislocation slip (including basal slip, cross-slip and pyramidal slip) jointly controlled the creep behavior. Various creep mechanisms led to the easy creep strain increment and the poor creep resistance. In regard to the PC sample, the thermal stability of the preset twins was inferior and twin widening happened, resulting in a faster increment in the creep strain and a poorer creep resistance. With respect to the PC-AA sample, the dominant creep mechanisms were basal slip and dislocation climb. The high-density particles inside the preset twins successfully delayed cross-slip and twin widening, leading to the enhanced creep resistance. Thus, the twins induced by the pre-compression and the particles inside the twins induced by the subsequent peak-aging successfully enhanced the creep resistance of the dilute Mg-Nd alloys.

The creep behaviors of dilute Mg Y alloys have been deeply explored whereas very few researches concerned Mg Y series with high Y concentration. The influences of static precipitation and precipitate-free zones (PFZs) on the creep behaviors are still rarely reported. In this work, the compressive creep tests were performed on the as-solution (AS) sample and the as-aged (AA) sample in a hot-rolled Mg-10.5wt%Y alloy at 493 K, 523 K and 553 K under various stresses. It was found that the creep mechanisms for both AS and AA samples appeared to be independent on the creep temperatures. Specifically, the dominant creep mechanisms of AS sample were twinning and dislocation climb. While the creep behaviors of AA sample were ruled by cross-slip and pyramidal slip. Dynamic precipitates were formed in AS sample during creep, but they could hardly delay the dislocation movement and twinning. On the contrary, the static precipitates could dramatically retard the cross-slip and interact with pyramidal dislocations in AA sample. Besides, no PFZ was found at 493 K, but PFZs were gradually formed with the temperature rising. At 523 K, PFZs were randomly developed in both AS and AA samples. At 553 K, PFZs were uniformly developed in both AS and AA samples. The wider PFZs in AS sample further induced the deterioration to the creep resistance. It is believed that this work will enrich the theoretical basis and expand the applications of heat-resistant Mg Y based alloys.

This work proposed a practical method, interrupted compression with an intermediate annealing, for optimizing the mechanical properties of Mg–4Y-2Nd-0.2Zn-0.5Zr alloy. This method contained the first compressive step for an interrupted strain of 0.25, the intermediate annealing for 5 min, and the second compressive step for a total true strain of 1.6. The temperatures for the two steps of hot compression and intermediate annealing were the same. The obtained sample was named IC sample. As a comparison, the continuous compression was also performed (CC sample). During hot compression, the work softening of the CC sample was dominated by the rotational dynamic recrystallization (rDRX) and the twin-assisted DRX (tDRX). With the strain increasing, the rDRX acted a more dominant role compared to the tDRX. In the IC sample, the intermediate annealing triggered the formation of deformation bands. During the second compressive step of the IC sample, the work softening was dominated by the DRX assisted by deformation bands besides the rDRX. As a result, the volume fraction of ultra-fine grains (VUFG) was much higher in comparison to the CC sample. Compared to the grain size of UFGs (DUFG) and the basal pole distribution, the VUFG had a more important role in the resultant mechanical properties. The higher VUFG of the IC sample led to the better combination of strength and ductility at each compressive temperature. Comparing the IC sample to the CC sample after compressing at temperatures from 420 °C to 510 °C, the increments of the UTS were 7.4%, 2.4%, 1.2% and 0.4%, and the increments of the FE were 4.0%, 13.9%, 22.8% and 21.3%. The interrupted compression with an intermediate annealing had a deep potential in applying to other Mg alloys despite the initial texture.

In this work, the tensile creep anisotropy was investigated in a hot-rolled Mg-5.5 wt%Y alloy sheet. The loading directions were performed along rolling, transverse and normal directions (RD, TD and ND), respectively. The results showed that a poor creep resistance was obtained along ND due to serious stress concentration induced by high-density twin boundaries blocking dislocations. While a similarly excellent creep resistance was obtained along RD and TD due to pyramidal slip contributes to the strain hardening during creep process. Meanwhile, this work found that an addition of 5.5 wt%Y could enhance the crack resistance of grain boundary over that of twin boundary. When twin boundaries were heavily generated to block dislocations during tensile creep, crack initiation occurred rapidly. It is suggested that both the density of twin boundaries and the Y content should be considered for improving the creep resistance of Mg Y based alloys.

Proper management of electronic waste (e-waste) represents significant economic and environmental challenges because of the tremendous quantity of e-waste, the potential of extracting precious metals from recyclable electronics, and the risks of environmental contamination with a variety of toxic compounds. This study focused on the leaching potential of 57 elements from central processing unit mainboards manufactured over time (1980s–2010s) using river water at different pHs as an environmentally-relevant extractant. The exposure time was set to one week. The calculated contamination factors allowed classification of the elements released from mainboards into five groups with increasing leachability and thus environmental concerns. Also, the results demonstrated a changing nature of e-waste related to the technologies employed and the transition of metal contamination signatures from these electronics; newer computer mainboards have a lower risk of Pb and Sn leaching but a greater release of Li, Sb, and a few rare earth elements (Sm, Eu, Dy). These specific patterns of elemental release could become powerful geochemical forensic tracers of improper recycling activities of e-waste in the environment. Most studies until now have investigated just a few key contaminants, despite the cocktail of pollutants contained in electronics. Therefore, a full assessment of the leaching potential of pollutants from non-properly recycled e-waste and further ecotoxicological studies are timely needed.

The development behaviors of ultrafine grains (UFGs) due to continuous dynamic recrystallization (cDRX) were investigated in hot compression of a Mg-4Y-2Nd-0.2Zn-0.5Zr alloy pretreated in solution and subsequently peak-aging. In the aging sample containing statically precipitated particles (SPPs), the occurrence of cDRX starts to take place at medium to high strains, and finally a stable size of UFGs are fully developed in a whole volume. In the as-solution sample with no SPPs, by contrast, the size of UFGs evolved increases rapidly at lower strains, slowly at medium strains and then finally shows a bimodal distribution in high strain. In the latter, smaller grains accompanying with an incomplete formation of UFGs are developed by any effect of dynamically precipitated particles (DPPs). The microtexture evolved is effectively randomized in the regions of UFGs, leading to the formation of a weaker texture. The tensile elongation of the aging sample, with SPPs and fully developed UFGs, was around 17.4%. This was much higher than that of the as-solution one, with no SPPs and incompletely developed UFGs, that was 11.8%, which might result from the more randomized texture due to fully developed UFGs. Keywords: Precipitation particle, Hot compression, Microstructure, Dynamic recrystallization, Microtexture, Mechanical properties

Microstructural development under interrupted hot deformation of a cast Mg–Gd–Y–Zr alloy was investigated by optical microscopy (OM) and electron backscattering diffraction (EBSD) technology and the resultant mechanical properties were detected through tensile tests at room temperature. Ultrafine grains (UFGs) were remarkably developed under the condition of interrupted hot forging, resulting in an improvement of ambient mechanical properties. The basal texture was weakened by an effective increase of the volume fraction of UFGs under interrupted hot forging. These resulted in an improvement of tensile ductility with little or no drop in strength, i.e. the volume fraction of UFGs was raised from 30% to 70%, leading to an increase of the ambient tensile elongation from 15% to 23%.

Mg-RE based alloys usually exhibit better creep resistance than traditional RE-free Mg alloys. Creep anisotropy can be still found in Mg-RE alloys but barely investigated. Thus, in the present study, tensile creep anisotropy and creep mechanisms were studied in a dilute Mg-2Y alloy extruded sheet. It is found that tensile creep property shows not only obvious stress and temperature dependences but also strong anisotropy. Varied stress exponent n is obtained under different conditions. Under σ 40 MPa at all temperatures, n > 4 is seen and intense dislocation slip becomes the predominant deformation mode. Besides, steady-state strain rate e ˙ s and n are always higher along ED than TD. This creep anisotropy is caused by different dislocation slip types. Basal slip plays the most important role in the creep anisotropy under σ 40 MPa. Heavy basal slip and pyramidal slip are the main mechanism during the creep along ED while cross-slip of dislocations plays the dominant role along TD. Furthermore, { 10 1 ‾ 2 } anomalous twins are more likely to be found in samples crept along ED with a smaller Schmid factor for twinning. Anomalous twinning and pyramidal slip contribute to the creep fracture of ED sample. Unlikely, cross-slip composed by basal and prismatic dislocations induces the fracture of TD sample.

The effects of pre-compression on the creep behaviors along rolling direction (RD), transverse direction (TD) and normal direction (ND) of a hot-rolled Mg-4wt%Y alloy sheet were investigated in this study. A valid and convenient method for enhancing creep resistance and a systematic research in understanding creep anisotropy were provided. The pre-compression was carried out at 298 K along TD and performed to a true strain of 0.07. The samples with pre-compression (PC) and without pre-compression (NPC) were labeled as NPC-RD, NPC-TD, NPC-ND and PC-RD, PC-TD, PC-ND, respectively. Compressive creep tests along different directions were carried out at 523 K under various applied stresses. The results showed that both NPC and PC samples had obvious a three-dimensional creep anisotropy. The sequence of creep resistance of NPC samples was ND > TD > RD. The dominant creep mechanisms of NPC-RD and NPC-TD samples were both cross-slip and twinning. While dislocation climb and pyramidal slip dominated the creep of NPC-ND sample, resulting in the highest creep resistance among the three NPC samples. After pre-compression, the resultant sequence of creep resistance of PC samples was RD > ND > TD. Dislocation climb and frequent twin intersections became the dominant creep mechanisms and significantly enhanced the creep resistance of PC-RD sample. Due to detwinning, only a slight enhancement of creep resistance happened in PC-ND sample. The creep resistance in PC-TD sample perceptibly declined, because heavy cross-slip and stepped dislocations accelerated the creep strain. Although the three-dimensional creep anisotropy still insisted in PC samples, pre-compression was manifested to be an excellent method for improving creep properties along the worst direction (RD).

In this work, Mg-xY-2Nd-0.2Zn-0.5Zr (x = 0, 2, 4, 6 and 8, in weight percentage) alloys were subjected to hot compression at various temperatures from 420 °C to 510 °C. For briefness, the studied alloys were named as 0Y, 2Y, 4Y, 6Y and 8Y samples. During hot compression, dynamic recrystallization (DRX) happened and ultra-fine grains (UFGs) were generated in all samples. With the increase of Y content, the volume fraction of UFGs became lower. Based on the origins of work softening during hot compression, the samples could be classified into two groups. Low Y-containing group included 0Y, 2Y and 4Y samples, while high Y-containing group included 6Y and 8Y samples. Continuous DRX (cDRX), which was accompanied by deformation bands, induced the work softening of low Y-containing samples. Inversely, for high Y-containing samples, high-density dynamic precipitates consumed the stored energy and induced the work softening. The cDRX development was delayed, and discontinuous DRX (dDRX) happened at the dynamic precipitate sites at high strains. For the hot-compressed samples, during uniaxial tensile tests at room temperature, basal slip dominated low Y-containing samples while pyramidal slip dominated high Y-containing samples. The strong interactions between pyramidal dislocations and precipitates enhanced the strength of high Y-containing samples by sacrificing elongation.

The artificial plasmon-polariton bandgaps were studied and manipulated at infrared frequencies. The polaritons were facilitated by manifesting the strongly coupled states among electromagnetic wave and the induced electric dipoles in two-dimensional (2D) indium-tin-oxide nanorod arrays (ITO-NRAs).

Bulk copper alloys with nano TiB2 particles were prepared by a new technology that combining in situ reaction with rapid solidification. Appropriate reactor shape and procedure parameters are as follows: S0/(S1 + S2) = 0.8–1.2, L0/D0 = 10–15, θ = 60–90°, melt temperature 1350–1450 °C, air pressure 0.2–0.3 MPa. A special water-cooled copper mold can satisfy the need of rapid solidifying Cu–TiB2 alloy melt. The average size of TiB2 particle in the copper matrix synthesized by using optimal parameters is about 20 nm.

Because of the integration of three networks in China, search requirements with multimedia information will increase. The contents on TV, computer and cell phone are different in format and protocol not to intercommunication and share. When the national policy demand makes the division up, the content provider must provide formats and adapter mechanisms which are intercommunicated. As precondition of Three Screen Adaption, TCP/IP PROTOCOL Monitoring's accuracy determines the effect of three screen fusion directly. In this paper, the methods of protocol monitoring are introduced firstly. With comparing, the existing monitoring's accuracy can't meet the requirement of three screen protocol adaption. Then a new protocol monitoring model in three screen protocol adaption environment is proposed and protocol recognizer is designed and optimized with HMM technique. It will simplify development and publishing information unified that three screen equipment access the same protocol monitoring model, which has important practical value and application prospect.

There are many common monitoring systems in Data Center (DC) to ensure devices' security and normal run, to promote DC's management and maintenance, and to lower the effect of human factors. Design of integrated monitoring system in DC should think all monitoring systems as a whole, in which server monitoring system is a core and DC asset management system is a base. An independent DR monitoring portal should be used to integrate all other monitoring systems, and these systems should be optimized.

Constructing Computation Grid Service System with idle computers in an organization to provide computation service for Mobile Agent can save funds of high-performance computing and make full use of idle resources, but Fault-Tolerance mechanism must be researched to guarantee running of computation task when nodes or networks of the system fail. Three main parts of Fault-Tolerance mechanism of the system are researched in this paper. An adaptive Fault-Detection mechanism, a non-close, non-block and low-overhead Checkpointing mechanism, and a Partial Rollback Mechanism Based on Communication Domain are proposed, which can save overhead of Fault-Tolerance. Experiments have shown their advantages.

Generalized data center can be established to manage and maintain heterogeneous application systems as a whole in university, which promotes capability of application services and reduces workload of other departments. Generalized data center's architecture based on network storage and backup technology is proposed, in which application systems are divided into fixed data and change data. Fixed data are backed up and change data are stored centrally, so that service can be recovered in short time and data of service are real-time when there is fault of software or hardware in application system. This architecture only needs 3 additional systems to ensure multiple applications' services. It is a low-cost, high-availability, high-dependability, high-performance, high-scalability architecture and fully meets requirements of universities and other similar enterprises.

Because of autonomy and intelligence of mobile agent, mobile agents can be used to take tasks of applications to access grid services in dynamic heterogeneous grid environments. According to the features of grid environment and mobile agent, a new TSP model is presented to describe mobile agent's migration in Grid and a new algorithm- bi-pheromone ant colony optimization algorithm is proposed to optimize mobile agent's migration in grid. In this algorithm, not only network load but also service nodes' ability and load are considered. Simulation experiments have proved that this algorithm can converge to shorter paths more quickly than traditional ant colony optimization algorithm in the new TSP model. This means it is a better path optimization algorithm for mobile agent's migration in Grid.

Grid is a research hot point in computer industry. In this paper, mobile agents are used as carriers of distributed tasks in grid, which can migrate between grid services autonomously and intelligently. Some mobile agents transmit a great deal of data in high-bandwidth and high-delay grid environment. According to features of grid and mobile agents, a new multiple connection mechanism is proposed. Experiments have proved that this mechanism, in which both transmission delay and package loss is thought as indicator of congestion, have higher transmission speed than the mechanism in which only package loss is thought as indicator of congestion.