Multiphase microstructure which contains ferrite, lath martensite, tempered martensite and a specific proportion of retained austenite with chemical composition of Mn between low Mn and medium Mn (0.14C-2.72Mn-1.3Si, mass fraction, %) belong to C-Si-Mn series was produced using continuous annealing simulator. By means of dilatometric simulation, SEM, TEM, EBSD and XRD, microstructures of the steels in different heat treatments were characterized. The results illustrate that the tested steel sheet gained good comprehensive properties with yield strength of 672 MPa, tensile strength up to 1333 MPa, total elongation A₅₀ of 13% after annealing at 800 ℃, which can be explained by the refined microstructure, appropriate proportion of phases and a specific proportion of retained austenite. This work has deeply analyzed the work hardening behavior, discussed the change of instantaneous work hardening rate n. The multi-stage work hardening behavior was studied by modified C-J analysis, and explored the influence of ( is the volume fraction of martensite, is the equivalent diameter of martensite) and fraction of ferrite on it. The results show that n increases with the rise of true strain and then decreases, but has a different feature in the decrease for the different tested steels; the multi-stage work hardening behavior studied by modified C-J analysis shows 2 or 3 stages because of the different martensite volume fraction. The strain scope of combined action of ferrite and martensite △e is affected by the volume fraction of ferrite: △e is small when the temperature is low, and then △e is large when temperature increases, while the △e maybe small when temperature continue to rise. Above all, the high instantaneous work hardening rate which is helpful for the improvement of strength, plasticity and toughness can be attributed to the proportion, morphology and distribution of ferrite and martensite, which is also the consequence of coordination and combination action of each factor.

Au/TiO₂ composite films with different pore sizes of antidot arrays are prepared by inversion replication of colloidal crystal templates. The microstructure and the photocatalysis performance of all samples are characterized by using SEM, AFM, XRD, UV-Vis and four-point probe. Relations between the coverage of antidot arrays on the surface of TiO₂ films and the diameters of template microspheres are discussed through calculation on geometric model of colloidal crystal templates and antidot arrays. The results show that the pore size of Au antidot arrays significantly influences the photocatalysis performance of the composite films. With the pore size increasing, the conducting ability and the charge carriers transport efficiency enhances. This is responsible for the improvement of photocatalysis performance. At the same time, the recombination probability of photoinduced electrons and holes increases during the charge carrier migration with the pore size decreasing, which result in the decrease of the photocatalysis performance. The photocatalysis performance increases rapidly and then decreases gradually with the pore size increasing, which is the result of the aforementioned two aspects of factors. The photocatalysis performance of the composite films reaches the maximum value when the pore size of Au antidot arrays is 3.3 μm.

Currently, Ni-based superalloys are widely applied to turbine blades or other components of gas turbines for their excellent high temperature mechanical properties. These components must exhibit a high level of resistance to the oxidation and corrosion conditions generated by the combustion environment. The general design philosophy is to select a high strength substrate alloy to withstand the stress and apply a surface coating to give maximum protection from the environment. In this work, a Cr-modified aluminide (Al-Cr) coating were prepared by combining arc ion plating and pack cementation aluminizing. As a contrast, a simple aluminide coating was developed by pack cementation aluminizing. The isothermal oxidation behaviors at 1000 and 1100 ℃ were investigated on the Ni-based superalloy DSM11 substrate, aluminide coating and Al-Cr coating. The results demonstrate that aluminide coating and Al-Cr coating are dense and adhere tightly to the substrate. The microstructures of aluminized coating and Al-Cr coating are divided in two distinguished areas: the outer layer and the interdiffusion zone. The outer layer of the aluminized coating is composed of b-NiAl and Ni₂Al₃ phases, while the Al-Cr coating consists of b-NiAl, Ni₂Al₃, a-Cr and AlCr₂ phases. The DSM11 substrate shows bad oxidation behavior at 1000 ℃ isothermal oxidation test. The aluminide coating and Al-Cr coating both possess good oxidation properties in this test. Compared with aluminide coating, Al-Cr coating exhibits much better oxidation behavior due to the formation of Cr(W) zones, which can delay the process of Al depletion by hindering the diffusion of Al from the coating to the substrate. As for 1100 ℃ isothermal oxidation test, a large amount of mixed oxides include NiCr₂O₄ spinel and a-Al₂O₃ form on the surface of DSM11 substrate. The oxide scale on the surface of aluminide coating is simplex a-Al₂O₃ at the initial stage, while prolonging the oxidation time it changes into less protective mixed structure composed of NiCr₂O₄ spinel and a-Al₂O₃ with massive internal oxidation, leading to great degradation and even failure of the coating. The surface of Al-Cr coating is covered with thick a-Al₂O₃ during the whole oxidation process. The localized scaling zones produced during oxidation are re-covered by newly formed a-Al₂O₃. It benefits from the third element effect of Cr, which implies that the Al-Cr coating degenerates primarily by consuming Al-reservoirs. Moreover, the presence of Cr can promote the selective oxidation of Al and the self-repair abilities of the coating.

Cold-drawn pearlitic steel wires exhibit ultrahigh strength and have important applications where high strength and wear resistance are required. The hypereutectoid compositions present a promising potential for increasing the mechanical properties, especially the strength. The austenitization process strongly influences the following pearlitic microstructure and thus the mechanical properties. Continuous heating is always used in the industrial processing. However, the austenitization of pearlite in hypereutectoid steels during continuous heating has not been investigated systematically. In this work, the dilatometer and DSC were employed to investigate the austenitization kinetics of hypereutectoid steels during continuous heating. Microstructure evolution was observed with SEM and EBSD. The dilatometer and DSC curves were analyzed with derivative method. The whole austenitization can be divided into five stages: initial microstructure, reverse eutectoid transformation, retained cementite dissolution, homogenization and homogeneous austenite. Tangent method was used for measuring the critical temperatures of different stages. Experimental determination of transformed fraction was obtained through the lever method. Calculation with Thermo-Calc and Dictra software was carried out for the austenitization and considered to be a reasonable result by comparing with the experimental data. There is a turning point for the reduction rate of cementite and formation of austenite at the finishing temperature of reverse eutectoid transformation, which is similar with the austenitization in low carbon steel and spheroidal pearlite of hypereutectoid steel. Effects of heating rates, initial microstructure and carbon content were studied by varying the relevant parameters. Higher heating rate increases the starting and finishing temperatures of reverse eutectoid transformation and widens the temperature range, has no effect on the finishing temperature of retained cementite dissolution, increases the finishing temperature of homogenization. Coarser initial pearlitic microstructure increases the starting and finishing temperatures, widens the temperature range for reverse eutectoid transformation, increases the finishing temperature for retained cementite dissolution and homogenization. Enhancement of carbon content has little effect on the reverse eutectoid transformation, but increases the finishing temperature for retained cementite dissolution and homogenization. The effects mentioned above on the austenitization kinetics were discussed for mechanism analysis and compared with the observations of relevant systems provided by other research.

Molten Salt Reactors (MSR) is one of the six most promising Generation IV fission reactors. In the ultimate goals, MSR should run at temperatures over 1000 K, and its neutron irradiation damage doses could reach 100 dpa or more for the core components. Hence, the evaluation of irradiation damage under high temperature for structural materials is of particular importance for ensuring the safe operation of MSR. It is generally accepted the structural materials used for MSR should be Ni-based alloys, especially the Hastelloy N alloy. Recently, the 316 austenitic stainless steel (316SS) was considered as a candidate structural material for MSR. In this study, bulk and TEM specimens of 316SS have been characterized by nanoindentation and TEM to determine the change of micro-hardness and microstructural evolution after 7 MeV Xe²⁶⁺ and 1 MeV Xe²⁰⁺ iron irradiation, respectively. The irradiation experiments were carried out at room temperature (about 22 ℃) and 600 ℃, and the ion fluences correspond to calculated peak damge dose of 0.62 and 3.7 dpa. The nanoindentation results for bulk specimens showed the irradiation induced hardening of 316SS irradiated at room temperature, and the hardenability increases with increasing ion damage dose. However, in the case of the irradiation at 600 ℃, the hardness of 316SS keep the same level with that of the unirradiated specimen. The recovery of irradiation induced hardening occurred at 600 ℃ compared with the room temperature irradiation. The TEM results showed that the presence of high number density of nanoscale dislocation loops, with the diameter of 3~8 nm, in 316SS irradiated at room temperature. The number density of these dislocation loops increase with the increase of ion damage dose. As far as the irradiated 316SS under 600 ℃, several solute clusters were observed with the size range from 4 to 12 nm, which a little larger than the dislocation loops. It should be noted that the number density is far smaller than that of the dislocation loops in former case. The radiation induced defects (dislocation loops, solute clusters) were believed to be responsible for the hardening in 316SS. The temperature effect of Xe ion irradiation to 316SS was discussed using the Orowan mechanism. The stronger diffusion of point defects caused by ion implantation at 600 ℃ was considered to be the main reason for the recovery of irradiation induced hardening, in which the vacancies and interstitials have greater probability for recombination and then disappear, resulting in the exiguous nucleation sites for the formation of solute clusters.

ASME P92 (9Cr-0.5Mo-1.8WVNb) is a key material for the main steam pipe and header with larger diameter and thick wall in ultra-supercritical (USC) plant, because of its low thermal expansion coefficient, good corrosion resistance, good fabricability and especially its high creep rupture strength. The Laves phase (Fe₂M) precipitates in service and plays complicated and controversial role in affecting and/or determining the creep strength of the P92 steel. The fine Laves phase particles may contribute to precipitation strengthening and decrease the creep rate in the primary and transient creep region, however, the subsequent coarsening of Laves phase reduces the precipitation strengthening. Thus, in order to provide a systematic and definite understanding of the creep properties, it is necessary to investigate the precipitation and coarsening behavior of the Laves phase in P92 steel. In this work, the Laves phase parameters of P92 steel, including volume fraction, mean diameter and number density, were measured using SEM-BSE and quantitative metallography methods during aging at 650 ℃ for 0~8000 h. The precipitate and coarsening kinetics were investigated based on the quantification of Laves phase in P92 steel. Furthermore, the martensitic lath stability during aging was observed by OM and TEM. Lastly, the influence of Laves phase evolution on the creep rupture strength was estimated from the change of Orowan stress during aging. The results indicate that SEM-BSE is a suitable method for measurement of Laves phase precipitates, and can achieve significantly statistical data when characterizing large particles comparing with the EFTEM, so that evaluate the kinetics of precipitation and coarsening of Laves phase. The Laves phase precipitates at grain boundaries preferentially during the 0~2000 h of aging and its final volume fraction is around 0.95%. Obvious coarsening of Laves phase is observed after aging for 3000 h and its rate is much greater than that of M₂₃C₆ carbides. Grain boundary diffusion may play significant role in much rapider coarsening of Laves phases than that of M₂₃C₆ carbides. The Laves phase has the most precipitate hardening in the P92 steel aged up to 1000~3000 h and this hardening would drop remarkably due to its fast coarsening after aging for 3000 h. The contribution of Laves phase particles to creep strength is much less than that of M₂₃C₆ carbides. The P92 steel has a sub-microstructure with clear lath and high density dislocations after aging at 650 ℃ for 8000 h due to the stable M₂₃C₆ carbides on sub-boundaries.

The P92 steel specimens were aged at 650 ℃ for 0~5000 h, and precipitates of the aged specimens were extracted from the matrix using carbon extraction replicas and potentiostatic electrolysis. The amount of alloy elements in extracted precipitates was determinded by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and EDS, then the redistribution of alloying elements owing to Laves phase formation was analyzed. The hardness of aged specimens was taken using a Brinell hardness tester. The damage evolution equation owing to solute depletion was obtained from the redistribution characteristic of alloying elements and its influence on the creep life of P92 steel was evaluated based on the physical CDM model. The results are as follows. Before aging, about 86% contents of W and Mo in P92 steel are supersaturated in matrix and the remains are in M₂₃C₆ carbides. The removing of alloy elements take place due to the precipitation of Laves phase during aging. The formation of Laves phase consumes mainly W and Mo in matrix, and has little effect on the compositions of M₂₃C₆ cabides and MX carbonitrides precipitated before aging. The partition coefficients of these two elements supersaturated in matrix reduce up to 50% on the completion of Laves phase precipitation, and the Cr content in the matrix decreases about 3.6% because the formation of the Laves phase consumes Cr. The precipitation of Laves-phase contributes to the significant decreasing of solution hardening, causes the creep life of P92 steel reduction of about 24% at 650 ℃, 100 MPa.

Nowadays, the events of bacterial infection, food poisoning and biological corrosion damage are increasingly arising. It is urgent to develop new antibacterial material to fight against the drug-resistant bacteria. In this work, Ag-bearing antibacterial duplex stainless steels were prepared by adding Ag or Cu-Ag alloy particles. The microstructure and distribution of Ag-rich phases and Ag electrovalence of the materials after solution treatment at different temperatures have been discussed in detail by ESEM, XRD and TEM. The antibacterial effects of the materials were tested by film-cover method, and compared with CD4MCu and Cu-bearing antibacterial duplex stainless steel. The results indicated that some Ag-bearing phases in diameter of about 8 μm in the matrix of the material prepared by adding Ag after the solution treatment at 1050 and 1150 ℃ were observed, and increasing temperature could not improve the solution solubility of Ag-bearing phases. In addition, some Ag-bearing phases in diameter of 45 nm was found in the matrix of the material after solution treatment at 1150 ℃. For the material prepared by adding Cu-Ag alloy particles after solution treatment at 1050 and 1150 ℃, the solubility of Ag-bearing phases increased with the solution temperature rising. And the smaller the Cu-Ag particles were, the easier the Ag-bearing phases dissolved. For the material prepared by adding Cu-Ag alloy particles in diameter of 150~300 mm after the solution treatment at 1150 ℃, Ag-bearing particles were completely dissolved into γ phase while some in diameter of about 18 nm were evenly distributed in a phase. Antibacterial tests showed that Ag-bearing antibacterial duplex stainless steels prepared by adding different sizes of Cu-Ag alloy particles exhibitted excellent antibacterial effect. The material prepared by adding Ag granules had the antibacterial effect.

Energy crisis and global warming demand development of high-performance structural materials to improve energy efficiency. For efficient energy conversion, the operating temperature and pressure of a heat engine used in boiler/steam turbine power plants should be as high as possible and materials used for the engine components must be able to withstand the high operating temperature. As such, next-generation structural materials simultaneously possessing higher creep strength and larger oxidation-resistance at elevated temperatures than those currently used are required. The conventional austenitic stainless steels, which rely on the formation of a tenacious Cr₂O₃ scale, would lose its protection capability at temperatures above 923 K, in particular in the presence of sulfur and water vapor. The alumina-forming austenitic (AFA) stainless steels are a relatively new class of dispersion-strengthened austenitic steels which showed superior oxidation-resistance to conventional stainless steels due to formation of the Al₂O₃-based protective scale at high temperatures. Recently, research focuses in this field have been mainly placed on high temperature oxidation-resistance, while little attention was paid to the mechanical property of these steels, particularly at elevated temperatures. In order to fully understand the deformation mechanisms at high temperatures, the recrystallization behavior in a typical AFA stainless steel under different conditions, including different annealing temperatures and durations, were investigated. The high-temperature mechanical properties of the AFA stainless steel samples heat-treated under different conditions were also studied. The sample was fully recrystallized upon heat treatment at 1473 K for at least 2 h and showed tensile strength about 130 MPa when tested at 1023 K with a strain rate 6.4×10^-7 s^-1. The specimen was partially recrystallized upon heat treatment at 1373 K for 0.5 h and exhibited a higher tensile strength of 150 MPa with decreased plasticity when tested under the same condition. Further investigation shows that the grain growth was influenced by the precipitation of NbC. The grain growth exponent, n, was determined to be 3 and the apparent activation energy for grain growth is 234.7 kJ/mol, which is consistent with that of the Nb diffusion along the grain boundary in the austenite.

As one of the most widely used integrated circuit (IC) lead frame materials, Cu-2.1Fe alloy (C19400) shows excellent comprehensive properties, such as 90° bend fatigue, 90° bend formability, corrosion-proof, solder ability and resistance of solder peeling off. As a successful medium-strength and high-conductivity copper alloy, the Cu-2.1Fe alloy is strengthened by precipitation hardening and work hardening. Metastable coherent g-Fe particles will precipitate from supersaturated copper matrix during aging. The effects of long-term aging at different temperatures on the g-Fe coarsening characteristics and the mechanical properties of Cu-2.1Fe alloy were investigated, by means of conventional TEM, SEM, hardness, tensile strength and electrical conductivity testing. The results show that solution-treated Cu-2.1Fe alloys can reach its peak hardness and maintain for a longer time when aging at 500 ℃. The maximum of strength occurred at a particle size of about 12 nm in mean diameter. The coarsening kinetics of g-Fe follows Lifshitz-Slyozov-Wagner (LSW) theory and the activation energy for growth is estimated to 222 kJ/mol. Furthermore, it is found that coherent Fe particles gradually evolve into semi-coherent and cubical particles after aging for a long time and at high temperatures. The aging strengthening effect of Fe particles is not significant, and the maximum increment of stress is about 100 MPa. The strengthening mechanism of undeformed Cu-Fe alloy is coherency strengthening during the under-aged stage and changes to Orowan mechanism during the over-aged stage. Experimental results are in agreement with theoretical predictions.

The changes of Pb-20%Sn alloy melt's electrical resistance under different temperatures (300, 400 and 450 ℃), different ultrasonic powers (400, 600 and 800 W) and different treatment times (3, 5, 7 and 10 min) were investigated. The results show that the ultrasonic treatment has a strong influence on the melt’s electrical resistance. When the ultrasonic treatment is applied, the electrical resistance decreases immediately; after the ultrasonic treatment is removed, the electrical resistance increases instantly, but it does not reach its initial value. There is a difference between this electrical resistance and the initial value. This electrical resistance will remain constant for a long time, and then slowly increases to the initial value. The stronger the ultrasonic power is, the more significant influence the ultrasonic treatment will exert, the larger the transient variation of resistance (ΔR) and persistent variation of resistance (Δr) will be, and the longer the effective time will be. With the temperature increased, both ΔR and Δr will increase, and the effective time will increase at first and then decrease.With the extension of ultrasonic treating time, the ultrasonic effect will increase gradually, but there is a saturation treating time.

Mg-Zn-Mn alloy has high hot cracking tendency (HCT), but few researches focus on its hot cracking behavior and mechanism. The effect of Mn on the HCT of Mg-6.5Zn-xMn alloys was studied by the designed equipment which can measure and record the subtle changes of temperature, shrinkage displacement and shrinkage stress during solidification in this study. The results indicate that the larger the maximum contract rate (v_max) and the stress accumulating coefficient (k), which are put forward to evaluate HCT, the higher the HCT is, and there is higher HTC when v_max or k presents at high fraction of solid. The v_max of Mg-6.5Zn-xMn alloy increases with the increase of Mn content, however its position move towards to lower fraction of solid, and the k reaches the maximum value and presents at high fraction of solid at 0.35%Mn, which means the greatest HCT in this composition. The hot cracks of these alloys initiated and propagated at final stage of solidification (with higher fraction of solid), and the intergranular feeding channels could be observed. The thicker the liquid film around grains formed by the low melting point phases and the finer the grains, the less the HCT of the alloy is. After dendritic separation, interdendritic bridging formed by the jointing of dendrite arms could enhance the adhesive force between grains at final stage of solidification. However, the break of interdendritic bridging due to the hindrance to grain contraction would result in the hot cracks.

In order to improve mechanical properties of age-hardenable Al alloys markedly based on the conventional processing conditions, a novel thermo-mechanical treatment, which was consisted of pre-ageing, cold-rolling and re-ageing, was proposed in the present work. The effects of the thermo-mechanical treatment on microstructure evolution and mechanical properties of the 6061 Al alloy were investigated further by hardness measurement, tensile testing, XRD, TEM and HRTEM. It was shown that both the increased strength and elongation of the 6061 Al alloy were achieved simultaneously by the thermo-mechanical treatment. Especially, after the combination of under-ageing at 180 ℃ for 2 h, cold-rolling with the thickness reduction of 75% and re-ageing at 100 ℃ for 48 h, the ultimate tensile strength and yield strength of the alloy were 560 and 542 MPa, respectively, and the elongation was about 8.5%. The strength increment of the thermo-mechanically treated 6061 Al alloy was attributed mainly to the additional introduction of dislocation strengthening, dislocation cell strengthening and high Taylor factor value except for precipitation strengthening as compared to the conventional peak-aged alloy. Furthermore, the improved elongation of the thermo-mechanically treated 6061 Al alloy was mainly due to both the re-precipitation of strengthening precipitates and slight recovery of dislocations during re-ageing, which increased the accumulation ability of dislocations during the tensile deformation.

TiAl-based alloys appear as potential competitors to steels and superalloys applied in aerospace and automotive industries due to their low density, high specific strength and stiffness and good oxidation resistance at elevated temperatures. As a new generation of TiAl-based alloys, high Nb-containing TiAl alloys have become a promising high temperature structural material due to their better high temperature strength and oxidation resistance than ordinary TiAl alloys. TiAl-based alloy components such as low pressure turbine blade and compressor impeller often serve in near steady conditions for a duration of time once peak operating conditions are achieved at high temperature. The components suffer not only from rapidly induced damage from start-up and shutdown cycles, but also from creep damage under sustained loading periods. Moreover, the possible interaction damage between fatigue and creep must be considered. Thus, the study of fatigue-creep interaction for TiAl-based alloys is of great practical importance. Large numbers of researches were focused on the fatigue or creep properties of TiAl-based alloys, however, the fatigue-creep interaction behavior was rarely reported. Therefore, the crack initiation and propagation behavior of a nearly lamellar Ti-45Al-8Nb-0.2W-0.2B-0.1Y alloy in fatigue-creep interaction was observed at 750 ℃. The cyclic loading tests were carried out using a mini servo-hydraulic fatigue machine in a SEM chamber. The entire process of crack initiation and propagation was observed. The load cycling was trapezoidal by applying a dwell time at the maximum tension stress. The results indicated that micro-cracks mainly occurred at internal grain boundaries in the form of creep void or fatigue micro-crack. The micro-cracks firstly extended along the grain boundary by absorbing the creep voids or the stress concentration around crack tips, then connected with each other forming a longer crack. As the crack was frustrated by grain boundaries of other orientations, the crack began to grow in the thickness direction. Meanwhile, the micro-cracks perpendicular to loading direction emerged. Eventually, the frustrated cracks interconnected resulting in fracture. Compared to the in situ SEM observations in fatigue deformation, the dwell time resulted in the increase of probability of grain boundary crack initiation and the changes of crack propagation path. Thus, the fracture mode transform from transcrystalline to intercrystalline and the fatigue lifetime significantly decreased. The model of the crack initiation and propagation behaviors of high Nb-containing TiAl alloys in fatigue-creep interaction was presented in this work.

GH984G is a new Ni-Fe-Cr base alloy which has been designed for use as superheater, reheater and header materials for boilers in 700 ℃ advanced ultra-supercritical (A-USC) coal-fired power plants. Compared with the CCA617, Nimonic 263 and IN 740 alloys, the GH984G is an economic alloy due to the elimination of Co and it containing more than 20%Fe. As a precipitation hardened alloy, the size of γ′ precipitates has great influence on the tensile properties. The γ′ precipitates become coarse during long-term thermal exposure. The coarsening behavior of γ′ precipitates is closely related with Ti/Al ratio. However, there are few investigations about the influence of Ti/Al ratio on the coarsening behavior of γ′ precipitates of GH984G alloy. Therefore, in this work, the coarsening behavior of γ′ precipitates and its influence on tensile properties of GH984G alloy with two Ti/Al ratios was investigated during long-term thermal exposure. The results show that the growth kinetic of the γ′ precipitates can be explained by Lifshitz-Slyozov-Wagner's theory of element diffusion controlled coarsening during long-term thermal exposure at 700 and 750 ℃. The rate of γ′ precipitates growth of the alloy with high Ti/Al ratio is higher. At 800 ℃, the rate of γ′ precipitates growth decreases with increasing the thermal exposure time. The coarsening behavior does not follow the Lifshitz-Slyozov-Wagner's theory. The reasons are attributed to the effect of elastic interaction energy and the depletion of γ′-forming elements in γ matrix. The Ti/Al ratio has no obvious influence on 700 ℃ tensile properties during long-term thermal exposure between 700 and 800 ℃. The 700 ℃ yield strength has no obviously decreases even if after thermal exposure at 700 ℃ for 10480 h. The ductility increases after thermal exposure at 800 ℃. The variation of strength and ductility is attributed to the coarsening of γ′ precipitation. The deformation mechanism is the moving dislocations shear γ′ precipitates and the stacking faults form in γ′ precipitates. The fracture mode is the mixture fracture mode. The Ti/Al ratio has no significance influence on the deformation mechanism and the fracture mode.

With the innovation of electronic technology, integration and miniaturization become the future developing direction of printed circuit board (PCB). Meanwhile, the corrosion problems of PCB also stand out more clearly, and even trace amounts of corrosion products will have a serious impact on the reliability of PCB. Under the actual condition for use, like sulfur-containing industrial environment, due to the diurnal temperature variations or/and the temperature field fluctuations for PCB itself, condensation phenomenon is likely to occur. Furthermore, as a result of the moisture absorption effect of granular deposit or supersaturated humidity, a layer of electrolyte solution will be formed on the surface of PCB, causing electrochemical corrosion. In this work, electrochemical impedance spectroscopy (EIS) and scanning Kelvin probe (SKP) techniques were used to study the corrosion behavior and mechanism of hot air solder leveling printed circuit boards (PCB-HASL) in a simulated electrolyte 0.1 mol/L NaHSO₃ and 0.1 mol/L NaHSO₃/Na₂SO₃ solutions with different pH values, and the influences of immersion time and pH value on the change of corrosion mechanism were discussed. Meanwhile, with the aids of OM, SEM combined with EDS, the nucleation and propagation processes of corrosion products on the surface of PCB-HASL were observed and analyzed. SEM and EDS results showed that the corrosion behavior of PCB-HASL in acid simulation solution was similar to pitting corrosion, and the corrosion pits were in a state of accelerated expansion at the early immersion stage. The corrosion products mainly consisted of oxides and sulfates of Sn. EIS and SKP analysis indicated that the PCB-HASL surface could be activated by NaHSO₃ solution and pitting nucleation process only occurred at the early immersion stage. In the neutral or alkaline solution system of NaHSO₃/Na₂SO₃, pitting corrosion couldn't occur, and the transmission of the electrolyte to the electrode interface through the oxide film was the control step of the corrosion reaction.

Great interesting is induced by high power pulsed magnetron sputtering (HPPMS) for its high ionization of the sputtered materials, while the complex discharge puts of its applications in industry. The HPPMS discharge behaviors of various materials with different sputtering yields (Cu, Cr, Mo, Ti, V and C) were studied. The discharges of all the materials show a phasic discharge characteristic of five continuous stages. However, the target voltage of the same discharge stage of the material increases firstly, and decreases then with the increase of the sputtering yields, exhibiting a missing of certain discharge stage. The statistics of the mean values, peaks and platforms of the target currents show that self-sputtering and stable platform happen easily to the materials with high sputtering yields which is suitable for the thin films deposition by HPPMS, whereas gas discharge is dominated in the discharge of the materials with low sputtering yields, which is difficult in the using of HPPMS. Additional, the target current is mainly contributed to the platform (metal discharge) to the materials with high sputtering yields and the peaks (gas discharge) to the materials with low sputtering yields, respectively.