The recent progress of plastic finite element method (FEM) and its application in rolling are introduced, including: (1) progress in rigid plastic FEM theory and application. It deals with the variational principle for rigid-plastic compressible materials, the uniqueness of extreme point of total power rate functional for hot rolling problem, and the examples of solving various rolling processes; (2) elastic-plastic FEM was used to analyze the normal longitude rolling and  the special rolling processes, such as wedge rolling, cross wedge rolling and skew rolling; (3) fast-FEM for modeling to control a rolling mill. Now it becomes true that a FEM calculation for one pass flat rolling could be accomplished within 50-100 ms, which means it is possible to meet the requirement of on-line use for the process control to the rolling mill instead the traditional mathematics models; (4) multi-scale FEM simulation for rolling using cellular automata (CA) and FEM. Here the CA was used to simulate the recrystallization and transformation, and the temperature field, stress field and strain field were provided by FEM; (5) using crystal plasticity FEM to simulate the texture evolution during rolling. The crystal plasticity theory was put into the framework of the finite element method, to simulate the plastic deformation process at the crystal scale. An example is given for modeling of rolling Al polycrystal and texture evolution during the deformation; (6) FEM simulation of the crack and inclusion behaviors during rolling. The research works on evolution of cracks on the corner, edge, surface and inside of a workpiece, also for the inclusion by FEM are introduced. Finally, an outlook has been made for the plastic FEM.

The composition characteristics of typical bcc β-Ti solid solution alloys with low Young's modulus were analyzed by using the cluster-plus-glue-atom model, in which an alloy structure is dissociated into a cluster part and a glue atom part, i.e. isolated clusters are linked with glue atoms. The cluster here is the nearest neighbor coordination polyhedron with a coordination number of 14 (CN14). It is confirmed that β-Ti solid solution alloys with low Young's moduli satisfy a universal cluster formula [CN14 cluster](glue atom)_x given by this model. Alloys, described by cluster formulas [MoTi₁₄]Ti, [MoTi₁₄]Nb, [MoTi₁₄]Nb₂ and [Mo(Ti₁₃Zr)]Nb₂, Ti-11.8Mo (mass fraction, %), Ti-11.2Mo-10.8Nb, Ti-10.1Mo-19.5Nb and Ti-9.2Zr-9.6Mo-18.7Nb were designed and the alloy rods with diameters of 3 and 6 mm were prepared by copper-mould suction-cast method, respectively. These suction-cast alloys possess monolithic bcc β-Ti structure. The introduction of low-modulus Nb as glue atoms weakens the cluster linking and decreases the Young's modulus. Further substitutions with low-modulus Zr reduces the Young's modulus to 72 GPa in the [Mo(Ti₁₃Zr)]Nb₂ alloy. Solution treatment plus subsequent water quenching decreases slightly the Young's moduli of the suction-cast alloys.

At present, long period stacking ordered (LPSO) structures in Mg-RE-Zn (RE=Y, Dy, Ho, Er, Gd, Tb, Tm) alloys have been focused on. According to some reports, Mg-Gd-Zn alloys are classified as type II, i.e., there are no LPSO structures in as-cast alloys, but LPSO structures appear after heat treatment. To further study the formation of LPSO structure in Mg-Gd-Zn(Zr)\linebreak alloys, a Mg_96.32Gd_2.50Zn_1.00Zr_0.18 alloy was prepared by ingot metallurgy (I/M) in this work. Based on OM, SEM and TEM observations, the as-cast microstructure of Mg-Gd-Zn-Zr alloy consists of α-Mg solid solution, lamellar 14H-type LPSO structure within α-Mg grains and dendritic eutectic structure at grain boundaries, in which the eutectic phase is the β-phase ((Mg, Zn)₃Gd)), thus, Mg-Gd-Zn(Zr) alloys should be attributed to type I, i.e., there are LPSO structures in as-cast alloys. During solid solution treatment at 500 ℃ for 35 h, a solid transformation, dendritic β-phase with fcc structure→lamellar X-phase with 14H structure, was observed at grain boundaries. During subsequent peak-aging treatment at 200 ℃ for 128 h, ellipsoidal β´ and rhombus β₁ phases precipitated within α-Mg grains. Tensile tests at room temperature and Vickers hardness tests show that the alloy solution-treated and aging-treated has higher mechanical properties, i.e., σ_b=290.7 MPa, σ_s=162.5 MPa, δ=10.35% and 108.0 HV. The improvement of mechanical properties are attributed to the composite strengthening-and-toughening effect of the 14H-type LPSO structures, and the β´ and β₁ aging phases.

Due to the rapid melting and solidification in laser molten pool, the laser solid forming (LSF) samples have generally much finer microstructure than that of the conventional cast, and are also free of macrosegregation. To date, more and more researchers have reported the application of LSF technology in the forming of superalloy, which contains some easily segregated elements such as Nb, Ti and Al. To prevent the molten pool from oxidation, the LSF process usually should be performed within a protective atmosphere. But in practice, the forming of oxidation-resistant metals are always performed in the air atmosphere and only the molten pool is protected by noble gas. Therefore, it is important to investigate the microstructures and properties of LSF materials prepared in the air and noble gas. In the present study, the microstructures, tensile properties and high cycle fatigue properties of LSF Inconel 718 alloy samples prepared in the air and argon atmospheres were investigated. It is indicated that the microstructures in as-deposited and heat-treated LSF Inconel 718 alloy samples prepared in both atmospheres are similar. The as-deposited microstructure consists of columnar dendrites grew epitaxially along the deposition direction from the substrate, and changes to the equiaxed grains after solution heat treatment due to the recrystallization. The tensile properties of the two kinds of the samples after heat treatment reached the standard for wrought Inconel 718 alloy. The tensile strength of the sample prepared in air is slightly higher than that of the sample prepared in the argon atmosphere, and the high cycle fatigue lifetime of the latter is 30% higher than that of the former, which is related to the fewer defects such as micro pores and small size oxide inclusions existed in the former. The lower high cycle fatigue property of LSF Inconel 718 alloy than that of wrought Inconel 718 alloy is attributed to the metallurgical defects and the coarsening and uneven distribution of the recrystallized grains.

Interstitial free (IF) steel sheet has been widely used in automotive industry for its excellent deep drawabilities, which are most strongly influenced by textures formed after annealing. It is well known that the conventional annealing texture of IF steel consists of partial $\alpha$ fiber texture (<110>//rolling direction, RD) and γ fiber texture (<111>//normal direction, ND) which benefits the deep drawabilities, i.e., the stronger the development of the γ fiber texture parallel to the sheet plane, the better the deep drawabilities. Recently, many results showed that the grain size distribution in IF steel during the grain growth has apparent influence on the properties, whereas the impact of the grain size distribution on the texture has not been well discussed. The present work uses EBSD to investigate the grain size and textures of small, medium and large grains of IF steel sample, which was cold rolled to a reduction of 80% and subsequently annealed at 710 and 770 ℃ for various hold times. The results showed that the impact of the annealing temperature is more important for the growth rate and texture characteristics of grain than the hold time, which means the growth rate and texture characteristics are entirely distinct at different annealing temperature. At the same annealing temperature, the textures of different groups of grain are similar at different hold times whereas its intensity increased with the duration. In different groups of grain, the relationships between the texture and the average grain size can be described by the empirical formula from the experiment data.

There are many discrepancies in the literatures concerning the martensite constitution in the α+β double phase titanium alloys after quenching, so the Ti-4Al-4.5Mo alloy was selected to analysis further the martensite phase transformation in the alloy. The results show that when the quenching temperature is above the (α+β)/β transformation temperature (925 ℃), the hexagonal martensite (α´) formed. With the decrease of quenching temperature, another kind of martensite with orthorhombic structure (α´´) appeared which can coexist with α´ in a certain temperature range. In the sample quenched at 800 ℃, the α´´ disappeared, and the alloy only contains α and β phases. The α´´ martensite reduced the hardness of martensite transformed structure remarkably. EDS analysis indicated that the content of β stabilized element (Mo) is not the only factor determining the martensitic type.

The reverse transformation to austenite is an important part in the heat treatment process of steels. The final microstructures obtained by quenching, normalization or intercritical annealing (e.g. for dual phase steels) are strongly dependent upon the reverse transformation kinetics and austenitic structure. Therefore, it is of considerable technical interest to study and control the kinetics of this transformation. In order to clarify effects of substitutional alloying elements on the kinetics of reverse transformation from pearlite, an Fe-0.6C binary alloy and Fe-0.6C-1 or 2M (M=Mn, Si) ternary alloys were used in the present study (hereafter denoted as 0.6C, 1Mn, 2Mn and 1Si alloys, respectively). The initial pearlite structure of each alloy has nearly the same interlamellar spacing of 0.17 μm. Thin sheets of 0.5 mm×5 mm×10 mm in size cut from the pearlitic specimen were firstly preheated in a salt bath at 923 K for 15 s, and then rapidly moved into another salt bath at 1073 K\linebreak for reverse transformation for various periods, followed by water quenching. The variation of Vickers hardness and microstructure evolution with holding time at 1073 K were examined. Ferrite region without cementite remains inside or neighboring to austenite newly formed during reverse transformation in the 0.6C and 1Si pearlitic specimens. It is indicated that continuous dissolution of cementite in ferrite and continuous diffusion of C atoms through ferrite into the growth front of austenite occur. However, pearlitic ferrite and cementite almost simultaneously disappeared in the 1Mn and 2Mn specimens. Reverse transformation from pearlite in the 0.6C pearlitic specimen at 1073 K is finished after holding for about 5.5 s. The reversion kinetics is retarded by the addition of Si. On the other hand, the reversion kinetics is slightly accelerated by the addition of Mn. The difference of acceleration between the 1Mn and 2Mn pearlitic specimens is small. From the viewpoint of 1D austenite growth in a pearlite lamella, austenite can grow without long range diffusion of Mn and Si in the Mn- and Si-added pearlitic specimens, respectively. It is supposed that austenite growth is controlled by carbon diffusion in those specimens. The addition of Mn or Si affects carbon diffusion by affecting carbon concentrations at the austenite/ferrite and austenite/cementite interfaces, resulting in changes in reversion kinetics.

By using liquid metal cooling method, the Ni-based superalloy DZ125 was directionally solidified under planar interface growth condition of drawing rate of 1.5 μm/s. The microstructures at different solidified fractions were examined by OM and SEM. The results showed that the solid/liquid interface is planar and the microstructure evolution undergoes three stages: the γ phase was formed as solidified fraction (f_s) was not more than 0.26, and the fine HfC phase sparsely distributed in γ matrix; the coupled γ/MC growth appeared as f_s ranged from 0.26 to 0.86, and the morphology of MC was fibrous or plate-like shapes; the γ/γ´ eutectic was obtained as f_s was more than and equaled 0.86 0.86, in which the octahedral MC was precipitated simultaneously. EPMA was used to determine the solute distribution along the longitudinal direction of the sample. The contents of Al, Ti, Ta and Mo increased with f_s increasing, while the contents of W, Cr and Co decreased. The analysis showed that the microstructure transformation is attributed to macro-scale non-uniform solute distribution which resulted from solute redistribution during directional solidification.

Ti-80%Ni alloy was prepared by laser solid forming (LSF) under different processing parameters. The microstructure of the alloy consists of η-TiNi₃ phase under low scanning rate v and power P. With the increase of scanning rate, TiNi(B2)+η eutectic appeared, and with the increase of laser power, η laths were broken into bulks and distributed along certain orientation, and (TiNi(B2)+η) devoiced eutectic+inter-lath (TiNi(B2)+η) eutectic appeared. The higher the power is, the finer the η bulks are. And the enhanced power leads to a growing up of (TiNi(B2)+η) eutectic volume fraction. The microstructure became much fine with increasing v and P, while the volumn fraction of hard-brittle η lath decreased, as a result, the laser formability and plasticity of Ti-80%Ni both increased.

Long fatigue crack propagating path in TC4ELI alloy with lamellar microstructure was studied by SEM. Statistics of angles between cracking path and α lamella exhibits that fatigue crack is apt to parallel α lamella or cross α lamella vertically, which will induce the ladder shape of crack propagating path. The parallel and vertical propagating patterns were interpreted with the weak α/β interface and the orientation of hcp α-Ti unit cell. Analysis of crack propagating path helps to understand the effect of microstructure on fatigue crack growth (FCG) rates. FCG rates tests with different microstructures reveal that in near fatigue crack threshold (ΔK_th) region the thickness of α lamella is the main influential factor on fatigue crack growth rate da/dN, and the da/dN seems impervious to β grain size. However, in Paris region the FCG rates are both influenced by grain size and lamellar thickness.

In order to regulate discharges of the ships' ballast water and reduce the risk of non-native species introduced from the ballast water, the international maritime organization (IMO) has developed international legislation, the ships' ballast water should be treated before discharge, and electrolysis has been developed as a promising method for ballast water treatment. However, the oxidative species such as Cl₂, HClO and NaClO generated during electrolytic treatment may not only kill the non-native aquatic species but also accelerate the corrosion of the ballast tank steel. In this paper, the effect of the total residual chlorine (TRC) concentration in 3.5%NaCl solution on the corrosion of Q235 steel was studied using mainly the open-circuit potential-time measurement (E_OC-t) and electrochemical impedance spectroscopy (EIS). Four TRC concentrations, 0, 5, 10 and 20 mg/L, which are around the concentration proved to be effective for removal of non--native aquatic species, were tested. Both the E_OC-t and EIS results suggested that the corrosion of the Q235 steel in 3.5%NaCl solution with or without TRC can be divided into three stages: rapid oxidation of steel, coverage of metal surface by oxide film, and breakdown of the oxide film and initiation of corrosion. The negative shift of E_OC and reduction of charge-transfer resistance (R_ct) of the steel immersed in the solutions containing low TRC concentrations such as 5 and 10 mg/L demonstrated that the corrosion of steel is slightly enhanced. The enhancement of corrosion is due to the increase of the depolarization concentration present in the solutions. But for solution with higher TRC concentration such as\linebreak 20 mg/L, both the E_OC and R_ct increased, suggesting retardation of the corrosion process. The retardation of corrosion can be attributed to the passivation of the steel surface due to the strong oxidation of the active species and the formation of compact corrosion product that covers the corrosion sites. This means that increasing TRC concentration to 20 mg/L does not accelerate the corrosion of the tank steel. Therefore, higher TRC concentration for on-board electrolytic treatment is allowable, which is beneficial for shortening the treating process and improving the removal efficiency.

Hardness (H) and elastic modulus (E) of 1 $\mu$m thick Cu film deposited on Si substrate were measured by means of nanoindentation technique. The E value of Cu film obtained by using single stiffness measurement (SSM) is consistent with that obtained from continuous stiffness measurement (CSM). However, the H value obtained from SSM is much smaller than that from CSM because of occurrence of significant creep during the holding period at ambient temperature. The analysis of loading curves shows that the substrate effect on hardness measurement appears as the indentation depth is about 528-587 nm, indicating the ratio of penetration depth to film thickness (about 0.5) is consistent with the finite element calculation.

Generally, the surface pretreatments such as sensitization and activation are necessary for depositing a nickel metal layer on oxide surface by electroless plating, however, for an oxide surface with porous structure it is possible that the pretreatment is not necessary. In this paper, only by use of the surface activity of porous structure, an electroless plated nickel layer can be prepared on the surface of microarc-oxidation-fabricated porous magnesium oxide film in a conventional electroless nickel plating solution, consisted of nickel sulfate as main salt and sodium hypophosphite as reducing agent. Furthermore, the phase, microstructure, electrical conductivity and corrosion resistance of the obtained nickel layer were characterized. The results indicate that the 5 μm-thick nickel layer is composed of fine and homogeneously distributed nickel particles, at the same time the microstructure of nickel layer is dense. Nickel layer spreads into the micropores on the surface of porous magnesium oxide film, so that an interleaving interface is formed at nickel/oxide interface. XRD results reveal that the nickel layer contains crystalline Ni and amorphous Ni-P. Four-point probe measurement indicates that the nickel layer exhibits well electrical conductivity. Meanwhile, polarization curve reveals that corrosion potential elevates notably due to the presence of nickel layer. During electroless nickel plating the nickel ions in solution were reduced and deposited in the micropores of porous magnesium oxide film under the action of reducing agent ions, so as to generate tiny primary nickel particles, subsequently, these primary nickel particles continuously grew and spread, and finally formed an entire nickel layer on oxide surface.

The study of residue time distribution (RTD) curve is usually one of the effective methods to estimate the flow characteristics in the continuous casting tundish. In the past, the analysis model for RTD curve of one-strand is usually applied to estimate the individual strand data in multi-strand tundish, but the result obtained by such a model can not agree with the physical fact sometimes. In this paper, an analysis model is proposed to analyze flow characteristics in multi-strand tundish. First, the whole RTD curve of multi-strand tundish is obtained by the individual strand data. Second, classic analysis model is applied to analyze the whole RTD curve of multi-strand tundish. Third, average residence time is chosen as a key parameter to estimate the similarity of flow characteristics of each strand in the multi-strand tundish. Such an analysis approach can avoid the occurrence of the negative dead zone. And the volume ratio of dead zone satisfies the physical facts.

Laser jet solder ball bonding (LJSBB) technology is a special soldering method developed in cooperation by Fraunhofer Ltd and PacTech Ltd in 1998 to fulfill the specific needs in the packaging of micro-electro-mechanical system (MEMS) and other functional micro-devices. However, the metallurgy characteristics and reliability of the solder joint produced by LJSBB has not been broadly reported. In the present paper, the commonly used Au/Ni/Cu soldering pads were bonded by LJSBB with Sn3.0Ag0.5Cu lead free solder. The effect of laser energy on the interfacial microstructure of solder joint was investigated by SEM and EDS. The reliability of solder joints was also evaluated by thermal cycle treatment and strength test. Results show that due to the limited heat provided by laser beam,  the Au layer of the commonly used Au/Ni/Cu soldering pad cannot completely dissolve into solder during LJSBB process, which leads to the formation of multilayered reactive structure of Au+AuSn+AuSn₂+AuSn₄ in the interface of solder joint. The AuSn₄ locates at the most outside of the reactive structure and presents a needle-like shape. In despite of the brittle nature of Au-Sn intermetallics, the as-soldered joints present a comparatively high strength. However, the strength of solder joint decreases significantly after 100 thermal cycle treatment and keeps nearly unchanged after even more thermal cycle treatment. Metallurgy analysis of joint interface reveals that the thermal cycle treatment plays the roles of promoting the dissipation of residual Au in joint interface through solid state inter-diffusion, and leading to the formation of a quaternary phase of (Au, Ni, Cu, Sn) in interface, which results in weakening of LJSBB solder joint.

Powder metallurgy (PM), as an important method of fabricating SiC particle reinforced aluminum matrix (SiC_p/Al) composites, has advantages in obtaining good interfacial bonding and enhancing tensile strength over casting or infiltrating method. The primary process of the PM method involves mixing, compaction and subsequent secondary plastic deformation. Especially, secondary plastic deformation is an important process to destroy the oxidation film on the Al particle surfaces and enhance Al-SiC bonding. However, the incorporation of the SiC particles restricts plastic flow ability of the composite and makes it difficult to be subjected to heavy single-step plastic deformation, such as single hot extrusion, hot rolling or hot forging. Instead, multi-step deformation is a critical processing approach for the SiC_p/Al composites with low deformability. However, the previous attentions were mostly focused on single-step processing, multi--step plastic deformation of the SiC_p/Al composites was seldom discussed. In this paper, 20%SiC_p/2009Al (volume fraction) composite was fabricated using a common PM method and the effects of double extrusion on the microstructure and tensile property of the composite were investigated. It is indicated that the double extrusion could refine the SiC_p size, align the SiC_p and increase the aspect ratio of the SiC_p, but did not exert critical effects of the grain size and <111> texture of the matrix. However, the average distance between the SiC_p along the extrusion direction increased after the double extrusion, more easily inducing a SiC_p-poor band which aligned approximately perpendicularly to the extrusion direction. This resulted in a decrease in the strength and an increase in the elongation along the extrusion direction.

The solidification experiment of Cu-25%Ag alloy used in high field magnet was carried out under high magnetic field, the precipitation of Ag in Cu-rich dendrites, the hardness and the electrical conductivity were investigated. It was found that the Ag phase precipitated exhibites continuous rod-like morphology in the larger Cu-rich dendrites, and exhibites discontinuous particle-like morphology in the smaller Cu-rich dendrites; the number of the Ag particles is more and the size is thinner in the sample solidified under 0 T than under 12 T high magnetic field. The hardness and electrical conductivity of the alloy have changed due to the size variance of Ag precipitates.

The corrosion behaviors of low alloy steel P265GH and carbon steel Q235 deposited with NaCl and NaHSO₃ under dry/humid alternative condition were investigated by FTIR, XRD, SEM and galvanostatic method. The results reveal that under present experimental condition, corrosion rates of low alloy steel and carbon steel decrease with prolonging time and their mass losses are almost identical. Besides, corrosion resistance of low alloy steel P265GH is not better than that of carbon steel Q235. The corrosion products formed on the two steels are mainly composed of δ-FeOOH, α-FeOOH, Fe₃O₄, γ-FeOOH and sulphate, among which δ-FeOOH is predominant. The existence of δ-FeOOH accounts for the decrease of corrosion rates of the steels.

Super304H austenitic heat resistant steel is based on 18/8 Cr-Ni stainless steel alloyed mainly with 3%Cu and a small amount of Nb combined with N, which is used as superheater/reheater tubes in ultra-super critical (USC) power plants all over the world, due to its good combination of elevated temperature strength with hot corrosion resistance. The excellent high temperature strengths of this steel are mainly contributed by the precipitation strengthening effect of fine Cu-rich phase. Comprehensive study of the characteristic of Cu-rich phase is very important to understand strengthening effect on this steel. However, the Cu-rich phase is very fine< and difficult to be detected at the beginning of precipitation. In this paper, three dimensional atom probe (3DAP) was used to study the early stage of precipitation behavior and the composition change in Cu-rich phase of Super304H aged at 650℃ for different times after solution treatment at high temperature. Cu-rich phase is formed from Cu-rich segregated rigion by the concentration of Cu atoms in it at very beginning stage of aging. Homogeneously distributed Cu-rich phase precipitates with about 1 nm radius are obviously detected after aging at 650℃ for 5 h. With increasing aging time, Cu-rich phase is growing slowly while other elements in the Cu-rich phase decreased obviously. The copper element has almost concentrated to 90\% in the center part of Cu-rich phase after 500 h aging. The homogenous distribution of fine Cu-rich phase in austenitic matrix effects excellent hardening with increasing aging time. The stability of fine Cu-rich phase is one of the most important reasons for keeping good strength of Super304H heat resistant steel at high temperature.

DO₂₂ phase with long period ordered structure is the main strengthening phase in Ni-Al-Cr alloy applied in high temperatures, as it hinders the slipping of dislocations during the deformation. Structure transformation from fcc to DO₂₂ during the ordering process and phase separation have been studied extensively, but there are only a few of reports on the phase transformation in early precipitation stage, especially on the phase transformation of metastable pre-precipitate. In this paper, the microscopic phase--field method was employed to study the pre-precipitate during the transformation from fcc to DO₂₂ in Ni₇₅Al₅Cr₂₀ alloy. The early ordering process of Ni₇₅Al₅Cr₂₀ alloy are simulated at four different temperatures, and the relationship between the order parameter evolutions of Cr and Al atoms on (001) and (002) planes of disordered fcc solid solution and structure evolution will be investigated. The simulation results demonstrate that the parent phase transformed into L1₀(M=1) pre-precipitate with long period ordered structure before DO₂₂  phase formed. At the early aging stage, the atomic ordering is proceeded on each plane as the atoms migrate on planes only, and the L1₀(M=1) pre-precipitate formed in the way of congruent ordering. Then, the further ordering of atoms on (001) plane was induced by the migration of atoms between different planes, and the pre-precipitate with L1₀(M=1) structure is gradually transformed into DO₂₂ phase. The incubation period and existent time of L1₀(M=1) phase are prolonged with the temperature increasing, as a result, the incubation period of DO₂₂ phase is longer when the aging temperature is higher, and the formation of L1₀(M=1) pre--precipitate is easier when the temperature is lower.