Thermal spray technique is one of the key techniques in remanufacture engineering. The thermal sprayed coatings are commonly used in remanufacturing applications, their initial performance and service lifetime are critical to the success of remanufacturing. In the present paper, structural integrity, lifetime and failure mechanism of plasma sprayed coatings were investigated. The influences of hydrogen gas flow, spraying powder and powder feed rate on porosity in coatings and their mechanical properties were described. The rolling contact fatigue (RCF) experiment was conducted to develop a method of life time prediction and to reveal the failure mechanism for plasma sprayed coatings. The results show that the structural integrity of coatings can be obviously influenced by spraying process and an optimal design of spraying process can remarkably promote the coating performance. For this purpose, the S-N curve was established based on the large sample space to be used to easily predict coating lifetime. It is found that corrosive pitting, spalling and hierarchical failure are the main failure modes, those results from asperity contact, subsurface defect propagation and shear stress distribution, respectively.

Antiperovskite manganese nitrides are a group of negative thermal expansion (NTE) materials that have been developed rapidly in recent years. They exhibit important potential applications due to isotropic NTE property, controllable coefficient of NTE and NTE operation temperature window, and good metallic and mechanical properties. In this review, state of the arts and recent development in the field of studying antiperovskite manganese nitrides have been summarized and commented, which consist of introduction of history, classification, preparation approaches, influencing factors and mechanisms of NTE for such materials. The prospects are also described for antiperovskite manganese nitrides.

For safe use of the equipments in power plants, creep life prediction of the material served at high temperature is an important issue. With the purpose of the existing problems in overestimation of creep strengths, it is essential to analyze the creep mechanism and the creep damage to material in serving. In the present work, through analysis on creep curves of the T/P91 thermal resistant steel served in the super critical steam conditioned thermal power plants, the creep mechanism and the creep damage of T/P91 steel during creeping at 600℃ were discussed, and CDM (continuum damage mechanics) model established based on the physical nature was used to simulate the creep curves of T/P91 steel under high stresses. The modeled creep curves are good in agreement with the experimental data.

High-entropy alloys are prospective functional and structural materials owing to their excellent electromagnetic and mechanical properties. In this paper, the quenched Cu25Al10Fe20Co20Ni25 alloy foils with the thickness of 50~70 μm are obtained via a single roller experimental apparatus. Furthermore, the microstructure and properties of alloy foils are studied and the rapid solidification joining is conducted by using a micro-type capacitor discharge welding machine. The results show that Cu25Al10Fe20Co20Ni25 high-entropy alloy presents a simple single-phase FCC structure and its as-cast microstructure is coarsening. Rapid solidification can make the grains fine remarkably. The microstructure of joint is characterized by rapid solidification, while the microstructure in nugget is coarse and has clear directivity compared with the ordinary nuggets. The base microstructure adjacent to nugget has no evidence of coarsening and the width of fusing zone is almost tending to 0. Penetrated crack is the main defect during welding of high-entropy alloy, which relates to the microstructural coarsening and directionality resulting from high-entropy effects as well as electrode press.

The impact fracture behavior of FH550 offshore platform steel was investigated by use of SEM, TEM and EDS. The experimental results show that the microstructure of as--rolled test steel is consist of low bainite and granular bainite, and tempered bainite is the main structure of this steel after tempering. The dimple fracture was observed on most of frature surfaces of samples, and and some inclusions, such as CaO and Al₂O₃, appear at the bottom of isometric dimples. Carbides inclusions more than 10 μm were found on the cleavage fracture surface of a few of samples which could aggravate the impact toughness, and result in the fluctuation of the impact energy as brittle particles. Micropore accumulating and growing and crack necking are the main way for propagation of cracks, however, shear crack propagation may be obstructed by the particle clusters generated during plastic deformation, increasing the crack propagation work. It is also found that the fraction of high angle grain boundaries is 79.3%, and the average grain size is 7.61 μm. High percentage of large angle grain boundaries and fine grain size are the key factors to obtain excellent impact toughness.

A cellular automaton (CA) model has been developed to simulate the microstructure
evolution of ASTM A216 WCA cast steel during solidification and consequent cooling process. In the
model, the thermodynamics and solute diffusion of the multicomponent system were taken into account
by using Thermo-Calc and Dictra software. The peritectic solidification, α-ferrite/austenite transition and
eutectoid transformation as well as the final microstructure can be predicted. To validate the model, a sand
mold step-shaped casting was produced and metallographic examination was carried out, in which the
content and the grain size of proeutectoid ferrite were measured by using OM, and the
mean interlamellar spacing of pearlite was measured by using SEM. It was shown that the simulated
results are in good agreement with the experimental results. As the cooling rate increases,
proeutectoid α-ferrite content increased, while the mean grain size of proeutectoid α-ferrite
and the average lamellar spacing of pearlite decreased.

A model for prediction of the dynamic recrystallization microstructure and properties evolution of hot deformed austenite for micro alloyed steel by cellular automaton (CA) was developed. The theoretical modeling of dynamic recrystallization was on the basis of dislocation density, and the nucleation and grain growth of dynamic recrystallization were considered. The microstructure evolution of austenite dynamic recrystallization, such as the grain shape, grain size and volume fraction, was predicted quantitatively and visually described. Moreover the distribution and variation of the dislocation density and flow tress were obtained. Meanwhile, the microstructure and variation of the flow tress of micro alloyed< steel during hot deformation were measured by experiments. The measured results were in good agreement with the CA calculation results.

Long computational time for thermo-mechanical simulation of welding distortion and residual stresses hinders the application of this technique in large welded structure. It is of urgent need to develop a high efficiency numerical simulation strategy for welding process. The traveling temperature function method, in which the quasi--steady state character of welding process was exploited, was applied in the present study to improve the efficiency of welding simulation. Also the temperature and temperature history dependent material property models were established and applied. The finite elements analysis (FEA) models of 4 types of cylindrical and conical aluminum alloy structures, with different geometric shapes and dimensions, were built to analyze. Traditional moving heat source models were also established for these 4 structures to compare with the traveling temperature function method. The welding induced distortions were predicted by both methods for all the structures. The time cost of the traveling temperature function method is less than 40% of that of the traditional moving heat source method. While the computed distortion trends and values of two simulation methods were consistent. Finally the validation experiments were carried out and the distortions were measured. The measured distortions were compared with the numerical simulation results of two methods. The comparison show goods agreement. The errors between computed results from the two methods and the experimental results
are no more than 10% for all types of structures. This indicates that the numerical simulation models are not only
highly efficient, but also suitable for different types of cylindrical and conical aluminum alloy structures. So the traveling temperature function method is a high efficiency numerical simulation method with abroad applicability. This is a beneficial attempt and a novel idea to driving numerical simulation method in application of the large welded structures.

Investment and suction casting represents a more cost effective route to produce automotive exhaust valves of γ-TiAl based alloys, but the castings have severe gas porosities in the preliminary suction casting. It has been conferred that the generation of the porosity defects in the castings is a result directly associated with the entrapped air during filling flow. In order to investigate the filling patterns and the entrapped air during the suction casting process of automotive exhaust valves of γ-TiAl based alloys, water modeling experiments have been done. The effect of three types of filling pressure control methods and two types of moulds on the filling patterns are systematically investigated in this paper. Results show that serious entrapped air occur during the filling flow with an rough pressure control method by means of the vents at the top of the moulds (called a general suction casting); Tranquil filling patterns are obtained under an accurate pressure control method (“gas charging” or “air leakage”), and if the gas charging flow is smaller than 1.7 m³/h or the air leakage flow is smaller than 1.5 m³/h, the entrapped air phenomenon disappear. Meanwhile, the general and the“air leakage” suction casting of TiAl automotive exhaust valves are implemented using the conclusions of the corresponding water modeling experiments, and the real casting results claim good qualitative agreement with that of the water modeling experiments. Finally, The reasonable explanation for the aforementioned results of the water modeling experiments is given using the filling kinetic principle of suction casting.

The lattice constants of the matrix phase γ and the precipitated phase γ'  in a wafer-like nickel-base single crystal superalloy DD10 were determined by four-axis X-ray diffractometer (XRD). The variations of the lattice constants and lattice mismatches of γ and γ'  phases in the alloy wafer with different thicknesses, i.e., different interphase restriction conditions were obtained. A critical thickness of the alloy wafer to reach an unstable stress state was defined based on the observed changes of lattice mismatch associated with a transformation of stress state from the 3D bulk state to 2D plane state. The lattice mismatches corresponding to different mismatch stress states were calculated. The lattice constants of the γ and γ'  phases under a relaxed non--mismatch stress state were evaluated based on certain assumptions. The results showed that after the thickness of the alloy wafer reached the critical value, the lattice constant of the γ'  phase decreased linearly with the decrease of the thickness, whereas that of the γ phase kept nearly constant, resulting in a linear increase of the absolute value of lattice mismatch. Accompanied with the thinning process, the crystal lattice misorientation and the mosaicity increased, the γ/γ'  interphase restraint reduced and the interphase stress relaxed, and the measured stress state changed to the plane state. The estimated critical thickness and the lattice constants under non-mismatch stress state could provide references for the design of the components and the measurement of the residual stress in the superalloy.

The high manganese TRIP/TWIP symbiotic effect steel exhibits excellent combination of strength and elongation due to the transformation-induced plasticity and twinning-induced plasticity. In this paper, by means of a Zwick HTM 5020 high rate tensile test machine, the mechanical behavior of 18Mn-3Al-3Si and 21Mn-3Al-3Si high manganese TRIP/TWIP symbiotic effect steels under dynamic condition, strain hardening rate, true stress and strain hardening exponent show fluctuating with the true stain change, which is caused by the interaction between strain hardening and matrix softening. The microstructure evolution of the specimen was analyzed by OM, SEM, TEM and XRD. The results indicate that the transformation route is γ→ε, ε→α, under high-speed deformation; hindering of high-speed deformation to slip, transformation from austenite to martensite, and refinement of austenite matrix due to deformation twins are the main factors of strain hardening; while adiabatic temperature rise effect, ε→γ reverse transformation and dynamic recrystallization of twins make the matrix softening.

Stress corrosion cracking (SCC) of X80 pipeline steel in a simulated solution of the acidic soil environments in Yingtan China was studied by means of potentiodynamic polarization curves, slow strain rate test (SSRT) and corrosion morphologies characterized by SEM. The results show that X80 pipeline steel has high SCC susceptibility in the simulated solution and the failure mode is transgranular cracking. The SCC mechanism would vary with the applied cathodic potential. When the applied potential is positive to about -930 mV, the SCC behavior is controlled by the combined effect of anodic dissolution (AD) and hydrogen embrittlement (HE), i.e. the SCC mechanism is AD+HE. However, when the applied potentials are lower than -930 mV, such as -1000 and -1200 mV,  the process of hydrogen evolution plays the dominant role in SCC occurrence, meaning that the SCC mechanism is HE under such applied potentials. Moreover, SCC susceptibility increases with decreasing applied cathodic potential. Compared with X70 pipeline steel in acidic soil environments, HE plays a more important role in affecting SCC occurrence.

Gravimeter, pycnometer, SEM, XRD, carbon analyzer, XFS and oxygen-nitrogen analyzer were utilized to study the production of magnesium aluminium oxynitride (MgAlON) by carbothermal reduction and nitridation (CRN) under different temperatures and its formation mechanism was also discussed in the present paper. The results show that all of the raw MgO are completely consumed to form MgAl₂O_4ss at 1100℃. At sintered temperatures higher than 1300℃, the CRN reaction is taken place, and MgAlON is formed by solid solving N into MgAl₂O_4ss. The consumption of Al₂O₃ during CRN reaction causes the particle size of Al₂O₃ in the sample heated at 1600℃ to be smaller than that heated at 1500℃. Finally, the monophase MgAlON is obtained at 1650℃ when all the graphite and Al₂O₃ have been consumed. Moreover, because of the solid solution of N into MgAl₂O_4ss, the amount of defects in the lattice of MgAlON is raised leading to the solubility of Al in MgAlON being higher than that in MgAl₂O_4ss. Lots of closed pores are remained in grains even if the heating temperature has been raised to 1800℃ due to higher volatile Mg partial pressure and the gas phase product of CRN reaction at high temperature.

Microstructure and pitting corrosion resistance of UNS S32304 duplex stainless steels welded joint with plasma-arc welding (PAW) were studied by means of OM, SEM, energy dispersive X-ray spectroscopy (EDX) and potentiostatic electrochemical technique. The results show that the microstructures of the heat-affected zone (HAZ) and fusion zone differ from the base metal greatly, with ferrite fraction greater than 70\%. Furthermore, a lot of nitrides are precipitated at the interface between ferrite and austenite phases and inside the ferrite grains. Consequently, pitting corrosion resistance of the welded joint declines obviously and pitting preferentially occurs at ferrite phase in the high temperature HAZ near the fusion line.

In order to describe the distribution characteristics of laser energy inside the keyhole reasonably, the ray tracing method is used to deal with the multiple reflections of laser beam in the keyhole and Fresnel absorption on the keyhole wall. The line-source based keyhole model is modified. The predicted shape and size of the keyhole are employed to determine the distribution parameters of the volumetric heat source for laser beam welding, which are applied to the combined heat source model for hybrid laser+ pulsed gas metal arc welding (laser+GMAW-P) process. Based on such an adaptive heat source model, the numerical analysis of quasi-steady state temperature field in hybrid welding of TCS stainless steel is conducted. The hybrid welding experiments of TCS stainless steel are carried out, and the predicted weld shape and size are compared with the measured results to validate the established thermal model for hybrid welding. It is found that the thermal model for hybrid welding of TCS stainless steel based on the predicted keyhole shape can well simulate the temperature profiles and weld formation. Besides, the thermal model is used to calculate the shape and dimension of heat-affected zone (HAZ) and thermal cycles at different positions in HAZ under different process conditions, and the characteristics of thermal cycles of TCS stainless steel in hybrid welding are analyzed, which lay the foundation for the prediction of microstructure and properties of TCS stainless steel weld joints.

The mechanical property variation and micro-structure evolution of 304L stainless steel subjected to treatment of a new method, the surface mechanical rolling treatment (SMRT), were investigated in both liquid nitrogen and atmosphere at room temperature. The grain refinement, phase transition and hardness of 304L stainless steel treated by SMRT were examined using OM, SEM, XRD, TEM and Vickers hardess tester. The results show that nano-grains are created on the surface of SMRT 304L stainless steel,  their sizes vary with treating conditions. Large numbers of intersections and mechanical twins are observed in the steel samples. Due to prominent martensitic transformation during SMRT, the hardness of samples is enhanced greatly and varies with increasing depth from surface. The SMRT method has its advantages compared with the traditional methods to generate thicker hardening layers than other traditional methods. It can be easily industrialized.

In the field of condensed matter physics and materials science, it is of great importance to investigate the microstructures, properties and solidification regularities of liquid metals. In the last few decades, the theories of solidification of binary alloys, such as dendritic growth and eutectic growths have been built. Great progress has also been made on the study of monetectic and peritectic alloys. But a solidification theory on ternary quasiperitectic alloys has not been established up to now. The study of the solidification process of quasiperitectic alloys will provide a basic work for solidification theories of ternary alloys.
The master alloy of Al-11.8Cu-24.22Mg was prepared from pure Al (99.99%), pure Mg (99.99%) and Al-54.2Cu in a resistance furnace under CO₂ and SF₆ (volume proportion is 40∶1) atmosphere. The melted alloy (840-850℃) was pouring into different quenching graphite crucibles at the same time, and the cooling curves were recorded by a sixteen channels temperature recorder. The graphite crucible was quenched into cold--water immediately for rapid cooling at the preplanned quenching temperature. After the experiment, the microstructures of the sample were analyzed by SEM, with EDS analysis.
The experiment result indicates that the primary phase is identified as S (Al₂CuMg) and the quasiperitectic phases are α-Al and T (Al₆CuMg₄). The solidification microstructure is composed of remnant primary phase, quasiperitectic phases, binary eutectic and ternary eutectic. Although the quasiperitectic phases and binary eutectic are composed of the same phases (α-Al+T(Al₆CuMg₄)), their structures are different. The former structure presents strip form and the later present dendritic form. The ternary eutectic reaction is suppressed and the remnant primary S phase is reserved in the matrix with non-equilibrating crystallization.

As a precipitation hardened unidirectionally solidified Ni-based superalloy, DZ125 has been widely applied as structure materials in advanced aeroengine for gas turbine blades and vanes. In present, the paper on the influence of solidification parameters on microstructures have been largely published, but unfortunately, few of them have focused on giving a direct comparison between directional solidification characteristics in liquid metal cooling (LMC) and high rate solidification (HRS). In this paper, the influences of processing parameters on microstructures of blade shaped castings prepared both by LMC and HRS technique were studied. The results show that the dendrite structure and γ' precipitate in castings prepared by the same method are refined with elevated withdrawal rate; in the same solidification conditions, the LMC castings have finer dendrite structure and γ' precipitate than HRS, the larger the disparity between primary dendrite arm spacings in LMC and HRS castings, the thicker wall thickness is or the higher the withdrawal rate is. It is found that higher temperature gradient in front of solid/liquid interface can be obtained by LMC, and its variation with elevated withdrawal rate, however, is smaller than that by HRS. The γ+γ eutectic fraction is lower for LMC castings than HRS castings except for withdrawal rate of 70 μm/s, only at which more severe segregation than HRS's occurs. Chinese script type MC flakes between dendrites in HRS castings are larger at withdrawal rate of 110 μm/s.

The corrosion behaviors of the extruded Mg-0.54Ca and Mg-1.33Li-0.6Ca alloys in simulated body fluids (SBFs) were investigated using weight loss, hydrogen evolution and pH value measurement as well as dynamic electrochemical technique. The microstructure and corrosion morphology of these alloys were discerned by means of OM and SEM, and their corrosion products were analyzed by XRD. The results show that the microstructure is composed of α-Mg matrix and secondary phases: Mg₂Ca and CaLi₂ for the Mg-1.33Li-0.6Ca alloy, while α-Mg and Mg₂Ca for the Mg-0.54Ca alloy. At the initial immersion stage, the corrosion rate of the Mg-1.33Li-0.6Ca alloy is slightly faster than that of the Mg-0.54Ca alloy, whereas at the subsequent period the Mg-1.33Li-0.6Ca alloy has a corrosion resistance higher than the Mg-0.54Ca alloy. Lithium let to the formation of a dense corrosion product layer, which consists LiH, Mg(OH)₂, MgCO₃, CaCO₃, CaMgCO₃ and CaMgPO₄ for the Mg-1.33Li-0.6Ca alloy, however, it consists of MgCO₃, CaCO₃ and CaMgPO₄ for Mg-0.54Ca. Pitting and filiform corrosions are the main corrosion types of these alloys in SBFs.