A low carbon Fe-0.25C-1.48Mn-1.20Si-1.51Ni-0.05Nb (mass fraction, %) steel exhibits the combination of high tensile strength and good elongation after treated by a novel quenching-partitioning-tempering (Q-P-T) process. The variation in volume fraction of retained austenite in this steel with strain is measured by XRD, and the deformed twin-type martensite plates are also observed by TEM, from which the transformation induced plasticity (TRIP) effect in this steel is confirmed. Based on the measurement of average dislocation densities in both martensite and retained austenite combined with TEM observation, the effect of dislocation absorption by retained austenite (DARA) is found in the low carbon steel, similar to that in the medium carbon steel proposed recently, from which the generation conditions of DARA effect is proposed, and the mechanism of retained austenite on ductility enhancement of high strength steel is clarified.

Nano-structured oxide dispersion strengthened (ODS) ferritic steels are the leading candidates of fuel cladding for future fast neutron feeder reactors due to their excellent radiation tolerance and high-temperature creep strength. A 14Cr-ODS steel was prepared by mechanical alloy (MA) and hot isostatic pressing (HIP) methods. The morphology and microstructure of MA powders and the microstructure of 14Cr-ODS steel were characterized by SEM, XRD, EDS and TEM. The results showed that during the MA, the size of powders increases with the increasing milling time (0-2 h), then decreases with the increasing milling time (2-70 h). The grain size decreases with the increasing milling time. The alloying elements and Y₂O₃ dissolve fully into Fe matrix during MA after 70 h. Three kinds of precipitates are observed in the consolidated 14Cr-ODS steel: very high number density of nanoscale Y-Ti-O-rich clusters, few pyrochlore structure Y₂Ti₂O₇ particles and some Cr-Ti-rich particles. The clusters exhibits good high temperature stability at\linebreak 1250 ℃ for 8 h, while the density of Y₂Ti₂O₇ precipitates increases.

A new casting Ni-based superalloy is used in industrial and aircraft turbine because of its high strength and excellent hot corrosion resistance at high temperatures (about 900 ℃). The effect of heat treatment process on its microstructure and mechanical properties of the experimental casting Ni--based superalloy was studied in the present investigation in order to improve its application level. The results showed that the stress--rupture lives were changed with the increase of heat treatment temperatures. After solution treated for 2 h, then cooling by air cooling, the stress-rupture life under the conditions of 760 ℃ and 660 MPa was the highest in the case of heat treatment temperature at 1220 ℃, while under the testing conditions of 980 ℃ and 180 MPa the stress--rupture life was the highest in the case of heat treatment temperature at 1180 ℃. The stress--rupture life decreased when being heat-treated at temperatures above 1220 or 1180 ℃. The tensile strength of the alloy was improved with the increase of heat treatment temperatures from 1120 to 1220 ℃, and was decreased in the case of heat treatment temperature at 1240 ℃. The experimental results also showed that with the increment of holding time from 2 to 8 h at 1120 ℃ the stress--rupture life increased under the conditions of 760 ℃ and 660 MPa, while it was decreased under the conditions of 980 ℃ and 180 MPa. It was found that the tensile strength was higher for the alloy being held for 2 and 4 h than that for the alloy being held for 6 and 8 h, and the stress--rupture lives changed with the different cooling ways. The mechanical properties of the alloy may be determined by the size, shape, distribution and volume fractions of γ' phase and γ/γ' eutectic.

Based on the classical nucleation theory, and considering the effects of heat temperature and preservation time on precipitation, the γ' precipitation model in nickel-based superalloy was established. In combination with the characteristic value data of γ' precipitation which was got by isothermal aging experiment of GH738 alloy, the relative accuracy of simulation result was verified. Results show that the classic dynamic model of the precipitation can better forecast that γ' phase of multiple complex nickel--based alloy system mainly precipitate by uniform nucleation. Further, precipitation model was combined with four typical superalloys GH80A, GH738, U720Li and DD407. The effects of the contents of Al, Ti and its ratio change on the precipitation of γ' were calculated and analyzed. Results showed that the better role of Al than Ti on equilibrium content. Under the premise of equal amount of Al + Ti, the increasing of Ti had a greater contribution to the driving force of precipitation and complete precipitation time, and increased the volume fraction of the beginning of precipitation, but reduced the size of precipitated phase.

Using NH₃·H₂·O and NH₄HCO₃ blended solution as a complex precipitation agent, (Y, Gd)₂O₃∶Eu³⁺ nano--particles were synthesized by co--precipitation reaction. XRD and SEM were applied to analyze the crystallization and morphology of the sample. The thermal decomposition curves of samples were analysed by TG-DTA at different heating rates. Results showed that under the conditions of pH=10 and reverse titration, the change process of (Y, Gd)₂O₃∶Eu³⁺ precursors is divided into three steps. The apparent activation energy of each step was calculated by using the Doyle--Ozawa and Kissinger methods. The calculated results are 191.54, 557.05 and 236.58 kJ·mol^-1. The dynamic equations have been also established. The activation energy of (Y, Gd)₂O₃∶Eu³⁺ grain growth is 35.58 kJ·mol^-1, indicating that  grain growing is primarily controlled by interfacial reaction during process of preparation.

With the increasing miniaturization of electronic devices and systems, the pitch size and dimension of solder interconnects become smaller, accordingly the current density in solder interconnects gets higher and this results in severe electromigration (EM) effect that may deteriorate the performance of solder interconnects. The studies on flip chip interconnects have shown that the configurable change of solder joints can significantly affect the electromigration behavior. In this study, the microscale Cu/Sn-58Bi/Cu joints with different geometrical configurations, i.e., right angle-type and line-type solder joints, were designed and the electromigration behavior of joints under a direct current of a density 1.5×10⁴ A/cm² were investigated by SEM observation, microanalysis based on focused ion beam (FIB) and finite element simulation. The focus was placed on clarifying the influence of the solder joint configuration on the electromigration mechanism of the joint in terms of atomic diffusion distance, microregional resistance change and the change of phases in anode and cathode. Results showed that for both types of solder joints after current stressing for 112 and 224 h, Bi migrated to the anode side and congregated there, while Sn tended to enrich near the cathode side; in particular for the right angle-type solder joint the microscale hillocks and microcracks occurred at the anode side caused by the compressive stress which was attributed to Bi congregation and the consequent volume expansion of the phase, while the microscale concave valleys and microcracks appeared at the cathode side caused by the tensile stress, and it was worth noticing that the phenomenon above happened non-uniformly along the interface in right angle-type joint. The microanalysis results revealed that the diffusion velocity of Bi atoms was faster than that of Sn under current stressing in the solder joint. Furthermore, observations and finite element simulation results showed that for the solder joint with an asymmetrical configuration like the right angle-type solder joint the electrons flowed toward the bottom corner of the joint where the resistance was smaller and thus the current crowding effect occurred, and this was the primary factor for causing the severe electromigration.

With the development of miniaturization of electronic circuits and occurrence of growing number of project failure cases, the corrosion behavior of printed circuit board (PCB) becomes a non-ignorable scientific issue under the hygrothermal condition with mold. In this paper, the corrosion behavior of unfinished PCB (PCB-Cu) and PCB finished by electroless nickel immersion gold (PCB--ENIG) in mold environment was studied using scanning Kelvin probe (SKP). The mold growth behavior was observed by stereo microscope and SEM, and the corrosion products were analyzed by EDS. The results showed that the number of mold increased on the surface of PCB-Cu and PCB-ENIG specimens under hygrothermal condition. After a growth cycle of 28 d, the new generation of conidium formed with good activity. After 84 d mold test, corrosion occurred on both two kinds of specimens and it was more severe on PCB--ENIG. Meanwhile the activity of mold was an inhibitor in the corrosion process of PCB--Cu and a promoter in the pore corrosion process of PCB-ENIG.

The distortions of C-ring and cut cylinder of austenitic stainless steel after water quenching were investigated using simulation and experiment methods. The results indicated that the accurate measurement of temperature had a major influence on interfacial heat transfer coefficient (IHTC) which is calculated using the inverse analysis method. The sparse data of the high temperature stage due to low sampling frequency resulted in the lower value of IHTC. The simulated distortion during water quenching was mostly decided by the change of IHTC. The simulation results showed that the trend and magnitude of distortion predicted by the IHTC_H (calculated from the data of high sampling frequency) agreed better with the experiments than that by the IHTC_L (calculated from the data of low sampling frequency). The further analysis showed that the IHTC at high temperature had the great influence on the calculated yield behavior of materials. The high values of IHTC caused that the work piece kept in the yield status at higher temperature and wider temperature range. So the simulation using the IHTC_H predicted more serious plastic deformation and larger rigid movement. Further analysis showed that the simulation result of distortions was sensitive to the variation of IHTC at the high temperature stage, while insensitive to the variation at the low temperature stage.

The structure evolution of atom cluster in copper melt and the microstructure of solidificated copper during the solidification process were investigated by using the molecular dynamics simulation method. It was found that the solidificated structure is composed of crystal phase and amorphous phase when the cooling rate is ranged from 10^12.6 to 10^14.5 K/s. All the structures of the growing crystal, the critical nuclei and the atom cluster in copper melt are the layer mosaic structure constructed by fcc and hcp structure, which indicates that the layer mosaic structure of copper originates from the nucleation. When the cooling rate is lower than 10^13.3 K/s, the atom number of hcp structure in the layer mosaic structure in the amorphous matrix is less than that of fcc structure, but when the cooling rate is higher than 10^13.3 K/s, the atom number of fcc structure in the layer mosaic structure is less than that of hcp structure. When the size of the atom cluster with the crystalline structure in copper melt is smaller than the critical size of the homogenous nucleation nuclei, radial distribution function cannot reflect out the feature of crystalline structure though the HA bond--type index have confirmed the presence of a certain number of atom bond of crystalline structure.

Accumulative roll-bonding (ARB) process is appropriate to manufacture nanocrystalline and ultrafine grained sheets and plates which are most widely used material shapes in the commercial and industrial fields. The ARB process was proved to be very effective in refining grains and enhancing the strength of aluminum, steels and copper. However, the ARB was used only for cubic materials and rarely for hcp structured metal. The information available in the literatures about the microstructure change of magnesium alloys during the ARB process is still very limited. ARB was applied to AZ31 magnesium alloy sheets in the present work. ARB procedures were repeated for up to 5 cycles. Before each ARB cycle, the stacked sheets were heated at 350 ℃ for 5 min in an electrical furnace near the rolling mill. The microstructure and texture evolution of an AZ31 during ARB were characterized by electron backscatter diffraction (EBSD). The results show that ARB is an effective grain refinement method for producing AZ31 sheets with fine grain structure. Significant grain refinement was achieved after 3 ARB cycles with average size of about 2.18 μm. Grain refinement almost occured during the first three cycles and the distributions of grain size became more uniform as the cycle number increased. The results confirm the existence of critical ARB cycles to obtain dynamic balance between grain refinement and grain growth during the ARB process. Fraction of high angle grain boundaries increased with the increase of ARB cycles. Continuous dynamic recrystallization (CDRX) including rotation dynamic recrystallization (RDRX) occured during ARB of AZ31 as the grain refinement mechanisms. The dynamic recrystallization of AZ31 was activated and enhanced by the accumulated severe strain and shear strain across sheet thickness during ARB. In addition, large strain rate during ARB also contributed to grain refinement with the increase of Zener-Hollomon parameter. Microtextures of AZ31 tended to decrease and the average Schmid factor increased during the first three ARB cycles due to the sever and complex distrubution of shear strain, rotation dynamic recrystallization and rotating the new grains during ARB.

The most common manufacturing process for wrought magnesium alloy sheet is warm--rolling and the microstructure and properties of the product are strongly related with the rolling temperature. In particular, {1011}-{1012} double twinning is an important supplemental mechanism for the deformation of magnesium alloys during rolling at low or moderate temperatures. Therefore, the present work studies the microstructural variation of magnesium alloy sheets AZ31 rolled to 9% at different temperatures in the range of 150-350 ℃, and discusses the influence of rolling temperature on the quantity and variety of {1011}-{1012} double twins, as well as recrystallization related to the double twins. The mechanical properties of the rolled sheets and the influences of twins on the mechanical properties have also been discussed. The results show that {1011}-{1012} double twins are observed in the sheets rolled at temperature ranging from 150 to 300 ℃. The fraction of double twin per unit area, and the number of variant types within each primary twin, decreases with the increasing rolling temperature. At the temperature above 250 ℃, only co--planar double twins are observed in each primary twin. Recrystallized grains are observed to nucleate at the twin boundaries in the sheets rolled above 250 ℃, these can consume the twin boundaries and resulting in merging of the twin grains. No {1011}-{1012} twins are found in the AZ31 magnesium alloy sheet rolled at 350 ℃. With the increase of rolling temperature, the yield strength decreases and the ductile elongation increase for the rolled magnesium alloy sheet.

Due to the super light-weight property, Mg-Li alloys are very promising in the fields of aerospace and military defense. Up to now, many studies about hot deformation behavior of Mg-Li alloys have been reported. However, there are little researches on their room-temperature deformation behavior. Therefore, the plastic deformation mechanism of Mg-Li alloys needs further investigated. It is known that addition of RE to Mg alloys could cause solid solution strengthening, fine grain strengthening and secondary phase strengthening. Nevertheless, reports refer to the effect of RE on the texture of Mg-Li alloys. This work was devoted to study the microstructure, mechanical properties and the evolution of texture after compression at room-temperature of the as-cast Mg-5Li-3Al-2Zn and Mg-5Li-3Al-2Zn-1.2Y-0.8Nd alloys with OM, SEM, XRD, ODF and EBSD techniques as well as material testing machine. The results show that with the addition of Y and Nd, most of the filamentous AlLi intermetallic compounds are suppressed and substituted by other two intermetallics Al₂Y and Al₁₁Nd₃. Meanwhile, the grains are refined with the average size of\linebreak 30 μm. ODF analysis indicates that for Mg-5Li-3Al-2Zn alloy, when the strain is 0.17 the C-axis of most grains is roughly 75° form ND, while in Mg-5Li-3Al-2Zn-1.2Y-0.8Nd, when the strain is 0.10 the strong prismatic texture appeares, which means that the <1010> of most grains parallel to ND. Both of the two alloys exhibit high plasticity when tested at room-temperature, while the compression deformation of the alloy containing Y and Nd can reach up to 27%. The combined addition of Y and Nd significantly reduces the c/a of the magnesium lattice, weakes basal texture, activates the pyramidal slip system and, especially, activates the prismatic slip system which seldom occurs at room-temperature in magnesium alloys.

Three ternary alloys with composition of Mg-(11-13)Gd-1Zn (mass fraction, %) have been prepared and their microstructures and mechanical properties have been also investigated. The results showed that the as cast microstructure of the three alloys consists of α-Mg matrix, (Mg, Zn)₃Gd eutectic and a 14H long--period stacking ordered (14H--LPSO) phase. With the increase of Gd content the volume fraction of the (Mg, Zn)₃Gd eutectic increases. After extrusion the (Mg, Zn)₃Gd eutectic networks are destroyed and its broken particles are arranged in strips along the direction of extrusion, and the 14H--LPSO phase is distributed between (Mg, Zn)₃Gd strips. Solid solution treatment at high temperature above 500 ℃ results in the dissolution of (Mg, Zn)₃Gd phase into the matrix and the increase of the 14H-LPSO phase. After solution treated alloys are aged at temperature of 225 ℃ (T6 treatment) the volume fraction of the 14H-LPSO phase is further increased and both β' and β₁ precipitates appear in the microstructure. Aging of as extruded alloys (T5 treatment) also causes the formation of β' and β₁ precipitates but the volume fraction of the 14H--LPSO phase in the T5 treated specimens is lower than that in specimens after T6 treatment. High tensile strength combined with good ductility is obtained from the Mg--11Gd--1Zn alloy after T6 aging.

Al-B alloys are widely used in industries. Their manufacturing has attracted great attentions. Generally, the Al-B master alloys are manufactured by reacting KBF₄ with molten aluminum. A lot of work has been done to investigate the effects of reaction technologies on the manufacturing of Al--B alloys. But little attentions were paid to the reaction mechanisms at the interface between the aluminum melt and the fluoride salt. The interfacial reactions between Al and KBF₄ play a critical role in the production of Al--B master alloys. Investigations on the interfacial reactions in four different KF-AlF₃ solvents were carried out. It was demonstrated that a boride layer formed at the interface for all the four solvents. There existed AlF₃ between the boride layer and the aluminum melt when the eutectic KF-AlF₃ solvent or the hypereutectic solvents were used. AlF₃ formed by the reaction  between BF₃ and Al.

Cu-Ni alloy has excellent corrosion resistance in marine environment and so it is widely used as seawater pipework in ships; however its corrosion resistance will decrease rapidly in sulphide--polluted seawater. Benzotriazole (BTA) is an excellent inhibitor for corrosion of copper and its alloys due to the formation of passivation film of Cu(I)BTA. In this work, passivation film was prepared on B10 Cu--Ni alloy in compound BTA passivant for improving its corrosion resistance against sulphide--polluted seawater. Corrosion resistance of the passivation films was studied by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS); surface wettability of the films was characterized using contact angle test; X--ray photoelectron spectroscopy (XPS) was used to analyze the chemical compositions of the films. The results show that the passivation film prepared in compound passivant containing BTA and sulfosalicylic acid has better corrosion resistance than that in single BTA passivant; the higher corrosion resistance of the compound film results from synergetic effect of Cu(I)BTA and a complex compound which is a reaction product between sulfosalicylic acid and Cu alloy. Time and temperature of passivating treatment have important effects on corrosion resistance of the passivation film; prolonged treatment time and high treatment temperature are beneficial to improving corrosion resistance of the passivation film.

The nanocrystalline Fe₅₂Co₃₄Hf₇B₆Cu₁ soft magnatic alloys composed of bcc-Fe nanocrystals embedded in a residual amorphous matrix were obtained by the magneto-crystallization of melt-spun ribbons. In order to improve the soft magnetic properties of double--phase Fe(Co)--based nanocrystalline alloy, the nanocrystalline alloy specimens were vacuum annealed for 30 min at 100, 200 and 300 ℃. The results showed that the treatment of magnetic pulsing on the amorphous alloy resulted in the nanocrystallization, the grain size of precipitated α-Fe(Co) nanocrystallized phase was 5-10 nm. The low-temperature vacuum annealing of magnetic pulsed specimens further improved the soft magnetic properties of nanocrystalline alloy. The influence of annealing at 100 ℃ for 30 min on the properties is most obvious.

Reactor pressure vessels (RPVs) are usually made of low alloy ferritic steels, among which A508-III steel is a typical one. The long--term neutron irradiation can induce the embrittlement of RPV steels, and the embrittlement may lead to a reduction of the RPV service life. Generally, this behavior of the embrittlement is well established and is typically assessed by the increase in the ductile-to-brittle transition temperature (DBTT) of the RPV steels. For many years, extensive studies have revealed that irradiation-induced ultrafine Cu-rich clusters (CRCs) play an important role and CRCs with high number density cause hardening and embrittlement of the RPV steels. In order to investigate the effect of the precipitation of CRCs on DBTT of RPV steels by thermal aging, it is necessary to increase the Cu content in RPV steel. A 40 kg ingot of RPV simulated steel based on the composition of A508--III steel with higher Cu content (0.6% in mass fraction) was prepared by vacuum induction melting, and it was forged and hot rolled to a plate with 7 mm in thickness. Specimens with a dimension of 7 mm×12 mm×60 mm were cut from the hot--rolled plate. The heat treatment routes of the specimens consists of a soaking at 880℃ for 0.5 h, a water quenching, a tempering at 660℃ for 10 h, and a final aging at 370℃ for various times. The effect of the precipitation of CRCs on the DBTT of the RPV simulated steel was investigated by Charpy impact tests, as well as the microstructure analysis was carried out by TEM and atom probe tomography (APT). According to ASME 23 standard, Charpy-V specimens with a dimension of 5 mm×10 mm×55 mm were prepared and tested by TINIUS OLSEN 84 impact test machine. The TEM analysis shows that CRCs precipitate on dislocations in the specimen aged at 370 ℃ for 3000 h, and the clusters become a little coarsened when the aging time is extended to 13200 h. For the specimens aged for 1150 h, CRCs were on the stage of the nucleation assessed by TEM as well as APT analysis, and they did not have an effect on the DBTT of the RPV simulated steel. For the specimens aged for 3000 h, CRCs precipitated with an average equivalent diameter of 1.5 nm and a number density of 4.2×10²² m^-3, and it results in the increase of the DBTT from -100 ℃ to -60 ℃. For the specimens aged for 13200 h, CRCs slightly coarsened to 2.4 nm of the average equivalent diameter, while the number density is similar to that of the specimens aged for 3000 h. In this case the DBTT rose to -45 ℃. Therefore, the present work shows the precipitation of CRCs induced by thermal aging reveals a smaller impact on the DBTT than that by neutron irradiation. From the thermal aging aspect, the much lower number density of CRCs and the absence of the defects induced by neutron irradiation in the matrix could account for this phenomenon.

MCrAlY(M=Ni and/or Co) overlay coatings are wildly adopted on hot components in gas turbine engines to protect them from rapid oxidation. Various methods can be applied to prepare MCrAlY overlay coatings, which formed by the arc ion plating method possess outstanding properties in terms of interfacial strength, porosity and componential distribution, and thus excellent oxidation properties. To increase the Al content is deemed an economical and effective solution for enhancing the service performance and life for MCrAlY coatings at elevated temperature because the degradation process relies greatly on the ceaseless forming and spallation process of the protective α-Al₂O₃ scales during high-temperature oxidation. However, high content of Al will lower the melting point and decrease the ductility of the coating. This phenomenon can be partly resolved through a gradient coating design. In this paper, a conventional NiCrAlY coating and a gradient NiCrAlY coating have been prepared by the combined method of arc ion plating and subsequent diffusion treatment on Ni--base superalloy substrate. The microstructures, morphologies, isothermal oxidation behavior at 1000 and 1100 ℃ and cyclic oxidation behavior at 1100 ℃ have been investigated on the two kinds of the coatings. The results have revealed that the conventional NiCrAlY coating with uniform components is composed of γ'/γ phase, β-NiAl phase and some α-Cr precipitate phase. While the gradient NiCrAlY coating have showed layered microstructure, i.e., an Al-enriched outer layer and a Cr-enriched inner layer, primarily consists of β-NiAl phase, γ'/γ phase and some α-Cr precipitate phase in the outer layer. During the oxidation, it is evident that the vanishment of β-NiAl phase and the enlargement of γ'/γ phase for both the coatings. Nevertheless, the gradient coating has maintained higher Al content during long-term oxidation due to the massive β-NiAl phase obtained in the outer layer after vacuum annealing and the Cr(W) zones precipitated beside the Cr--enriched inner layer during the oxidation. Adequateβ-NiAl phase, as reservoir phase of Al, directly delay the process of Al depletion; Cr(W) zones, to a certain extent, slow down the degradation by hindering the diffusion of Al from the gradient coating to the substrate. As a result, the ability of forming and healing the protective α-Al₂O₃ scales in the gradient coating have been enhanced, which has eventually improved the high-temperature oxidation properties.