The quenching–partitioning–tempering (Q–P–T) process was developed from quenching & partitioning (Q&P) process and their difference are first described in this paper. The development of Q–P–T steels from ultrahigh strength to high strength–ductility is summarized. Novel Q–P–T process and conventional quenching–tempering (Q–T) process and their different effects on mechanical properties are compared. The micro–mechanism of the ductility enhancement from retained austenite in unltrahigh strength steels during deformation is emphasized in discussion, which is as a theoretical direction of microstructural design and control on the further development of advanced high strength steels.

The 2Cr13 martensitic stainless steel used in pumps and valves has been modified by plasma–based low–energy nitrogen ion implantation at a processing temperature of 450℃ for a treatment time of 4 h. The modified layer on the 2Cr13 stainless steel has a thickness range of 10—12 μm. The modified layer consists of monophase and has a high supersaturated nitrogen concentration up to 35%—40% (atomic fraction). The microhardness of the ε–Fe₂₋₃N phase layer was measured to be 15.7 GPa, and the increased wear resistance of the modified layer was obtained on a ball on disctribometer with a decreased friction coefficient from 1.0 of the original stainless steel to 0.85. A typical course from self–passivation to pitting corrosion of the modified layer in 3.5%NaCl solution was observed with a corrosion potential of −185 mV(vs SCE), a passive current density of 10⁻¹ μA/cm², and a pitting potential of −134 mV(vs SCE). The pitting corrosion resistance of the modified layer was improved in comparison with that of the original stainless steel with non anodic passivation. It was found that the plasma–based low–energy nitrogen ion implantation of 2Cr13 martensitic stainless steel provided an opportunity of combined improvement in wear and corrosion resistance for use in pumps and valves.

The effects of original preheating temperature of core, casting speed, preheating power and supplement heat power on unsteady state temperature field in high speed steel composite roll billet and the parameters match relationship during graphite mould continuous pouring process for cladding have been numerically simulated by use of interface and user–defined functions based on Ansys 10.0 and Fluent 6.3 software. The results indicate that the required induced preheating power increases with increasing casting speed and decreasing original preheating temperature of core when the finishing preheating temperature of core–surface is constant. The higher temperature zone only lies in the surface layer of core and the temperature in mostly zone of core is not affected by inducing coil when the core moves off the preheating coil. The highest temperature of core–surface and duration above its solidus increase with increasing supplement heating power and decreasing casting speed. When the casting speed matched with supplement heat power, the high speed steel can tightly bond with core to form the composite roll.

The effects of pouring temperature and casting speed on temperature field in high speed steel composite roll billet under copper mold and the selection of optimistic continuous casting technique parameters were studied by use of numerical simulation method based on Fluent 6.3 software. At the same time, the pouring billets experiment was also executed based on the simulation results. The results indicate that the casting speed and pouring temperature are the most important parameters to determine that a high speed steel composite roll billet can be well poured or not and the quality of interface of bimetal composite is better or not. Increases in pouring temperature and casting speed are conducive to metallurgical bond between the two metals, but their moreincreasing will make the depth of melting zone increase, the thickness of solidifying shell decrease and the feasibility of breakout increase. The simulated appropriate pulling temperature and casting speed are about 1873—1923 K and 0.3—0.5 m/min, respectively, which are proved by experiment results.

Because of climate and human factors, the corrosion of reinforced steel bar has become one of the important reasons of premature deterioration of concrete buildings and infrastructure. Stainless steel bar cannot be widely used due to its high price. Therefore, stainless steel clad carbon steel bar comes into being. It is a new material used in construction, which is made up of corrosion resistant stainless steel outer layer and carbon steel core. In the present study, an experimental study was conducted to investigate the mechanical property and bonding state of stainless steel clad carbon steel bar. The tensile strength of clad bar and bonding strength of two metals were measured using tension test and shearing test. Then, microscopic morphology, element diffusion and microhardness near the interface were analyzed using OM, SEM, EDS and microhardness tester. The results show that the two metals of the bar extend proportionally in the rolling process. The tensile strength is 550 MPa and the percentage of elongation is 45%. The neck phenomenon in the tensile experiment is obvious and the two metals are undivided in the fracture. With the increment of rolling pass, the bonding between the metals becomes denser and this increases the shearing strength. The max shearing strength is 333 MPa and the typical plastic dimples and shearing slip were observed on the shearing fracture surface.  Element diffusion occurs at the interface where the Cr, Mn, Ni of stainless steel diffuse into carbon steel and the Fe of carbon steel diffuses into stainless steel, and the total width of diffusion distance is about 30 μm. It makes the microhardness of the carbon steel near the interface increased significantly and the value is 399.4 HV which is higher than carbon steel after sixth pass rolling. Therefore, the metallurgical diffusion bonding is formed in the interface of clad bar.

Quasicrystal phase offers a good combination of strength and ductility due to the strong interface between the quasicrystal phase and the Mg–matrix. Hot compression tests of Mg–Zn–Al–(Y) based alloys reinforced with quasicrystal were performed on Gleeble–1500 thermal simulation machine at a constant deformation temperature of 230℃ and strain rates ranged from 0.0015 s⁻¹ to 1.5 s⁻¹. Microstructure evolution of hot–compressed Mg–Zn–Al–(Y) alloys and the relationship between flow stress and strain rate were studied. XRD and SAED results show that the microstructures of as–cast Mg–8Zn–4Al (ZA84) andMg–8Zn–4Al–0.5Y (ZAY8405) are composed of icosahedral quasicrystal phase and α-Mg matrix. The quasicrystals in ZA84 and ZAY8405 alloys have a stoichiometric composition of Mg38Zn43Al19 and Mg51Zn30Al19 respectively. Dynamic recrystalization (DRX) take place during hot compression and the flow stress increases with increase of strain rate at constant compression temperature, which can be represented by the Power Exponential Equation. Deformation twinning and dynamic recrystalization are easier to take place in ZAY8405 alloys due to the refined and dispersed quasicrystal phase with Y addition.

The gradient tritium permeation barrier was fabricated on CLAM steel substrate by hot dip aluminizing (HDA) and subsequent high–temperature diffusion treatment. The effect of Ce element on the microstructure and properties were investigated systematically. The Fe–Al layer with larger thickness and conspicuous serrated interface bonding with the substrate was achieved and the bonding strength of the coating was improved when the content of Ce increase. The gradient distribution of aluminized coating from surface to inter was obtained after thermal diffusion at 850 ℃for 4 h, the gradient coating reduces the thermal stress effectively. The result of the coating properties indicates that the thermal shock resistance and oxidation resistance at high temperature of the coating were also improved with the addition of Ce element.

Diamond–like carbon (DLC) coating has been widely used to modify the surface mechanical and tribological properties of materials. In most cases, a metallic buffer (e.g., Ti) is used as an interlayer between DLC coating and the substrate to improve the adhesion. In this work, the DLC coating was deposited on the AZ80 Mg alloy substrate using ion beam deposition technique. Specially, a pretreatment of microarc oxidation (MAO) was applied to the Mg alloy substrates to form the DLC/MAO composite coating instead of the metallic interlayer process. As a comparation, the DLC/Ti/MAO and DLC/Ti composite coatings were also deposited on the substrates. The surface morphology and roughness, mechanical, tribological and corrosion properties of the as–deposited coatings were studied. The results indicated that the DLC/MAO composite coating could significantly improved the hardness and wear resistance of the Mg alloy substrates compared with the MAO monolayer. Although the surface roughness of the DLC/MAO coating showed an increase due to the micropores of the MAO coating surface, the friction coefficient and the wear tracks exhibited a similar behavior to that of the DLC/Ti coating. Furthermore, the DLC/Ti/MAO/AZ80 system showed the best tribological properties among the current experimental samples. Meanwhile, the polarization curve revealed that the corrosion resistance of the MAO/AZ80, DLC/MAO/AZ80 and DLC/Ti/MAO/AZ80 film–substrate systems was greatly improved due to the existence of the MgO structure, which processed the high polarization resistance.

As an advanced manufacturing technology to produce hot rolled strips, compact strip production (CSP) process was developed at the end of last century and has been widely applied due to its high efficiency and low cost. Compared with the traditional technology, the advantages of CSP technology benefited from the refinement of austenitic grains and precipitation strengthening in the steels. This is because cooling rate is higher during the solidification of slab and the direct charging slab temperature is also higher in the CSP process, resulting in much higher solute contents in the solid solution before hot rolling than expected by the experiences from traditional steel production. So far, the Ti microalloyed steels produced by CSP process already have good performance and have drawn much attention on Ti precipitate behaviors and strengthening mechanism. However, the influence of alloying element Mn on the Ti microalloyed steels produced by CSP, especially the synergistic effect of Mn and Ti, was rarely reported. Therefore, in this work the microstructure and precipitate characteristics of two Ti microalloyed steels with different Ti and Mn contents produced by CSP process were studied by electron backscatter diffraction (EBSD) technology and high resolution transmission electron microscope (HRTEM). The results show that the steel with higher Ti and Mn contents has a higher frequency of small–angle grain boundary. Furthermore, the weight fraction of TiC precipitates with particle size smaller than 10 nm increases significantly, from 7.6% in the lower Ti and Mn steel to 26.1% in the higher Ti and Mn steel. However, the amount of Fe₃C precipitates decreases markedly. In addition, the strengthening mechanism analysis of the two tested steels show that grain refinement strengthening and dislocation strengthening make great contribution to the yield strength, while the precipitation strengthening is the primary reason which causes the difference in the strength between two tested steels.

The solidification microstructure of Mg–6Zn–3Y alloy under super–high pressure was investigated by SEM and EDS. The results show that solidification microstructure of Mg–6Zn–3Y alloy under super–high pressure (GPa level) could be evidently refined and was further refined with the increase of solidification pressure. Solubility of Zn in the alloy reached up to 1.64% under 4 GPa pressure which was increased by 44% than that under the atmosphere condition. Y is insoluble in the matrix, which resulted in a new phase riched in Y and granular phases which were dispersed in the matrix. The morphology of crystal changes follow this way: bulky branch crystal→superfine branch crystal→cellular crystal, and the growth of crystal changed from branch growth to cellular growth.

W–based composites were fabricated by spark plasma sintering (SPS) usingWpowders and carbon nanotubes (CNTs) as raw materials. The effect of the CNTs on the microstructure and room temperature mechanical properties of W was investigated. The results show that the W₂C was formed through the reaction of CNTs and W during the SPS process. The formation of the W₂C activated the sintering of W and enhanced the densification of W. On the other hand, the in situ formation of W₂C decreased the driving force of sintering and consequently inhibited the grain growth of W at high temperature. The grain size, relative density, bending strength and the Vicker’s hardness of W composites were 4 μm, 99%, 1353.9 MPa and 488.4 HV respectively when the content of CNTs was 0.5%.

Ultrafine grained (UFG) metallic materials arouse a great interest due to their great mechanical properties. Through the way of severe plastic deformation (SPD), including equal channel angular pressing (ECAP) and high–pressure torsion (HPT), the UFG materials obtained can be of obvious improvement in strength but of decrease in their thermal stability and ductility. In this article, the authors manage to obtain an UFG QBe1.7 copper alloy with great comprehensive properties by annealing the samples after being multi–directional compressioned (MDCed) at room temperature. The multiple tests were carried out using rectangular samples with consequent changing of loading direction in 90^? through three of mutually perpendicular axes from pass–to–pass. The deformed and subsequent annealed microstructures were investigated by OM, TEM and SEM/EBSD metallographic observations. The integrated flow curves plotted over a number of compression passes increase to a maximum at moderate strains of 1 to 2 followed by steady–state–like flow at high cumulative strains. Fine grains were not observed even at a higher cumulative stain of Σε=4.8, although there were many sub–grains when the samples were deformed to Σε=2.4. This indicates that the dynamic recrystallization or recovery was completely inhibited by fine precipitates. Static recrystallization (SRX) of the MDCed structure at 973 K was also investigated. With the increment of cumulative strains, the effect of grain refinement became more obvious, but the thermal stability was getting worse. At a medium strain of Σε=2.4, the minimal grain size of 0.8 μm can be developed with an excellent combination property. The formation of ultrafine grain is characterized by large–angle boundaries developed from low to medium boundaries. The change of the average grain size with annealing time can be divided into three stages: a recovery period for grain refinement, rapid grain refinement and normal grain growth.

{10¯11}–{10¯12} double twin is the most common twin type being observed in the rolled AZ31 magnesium alloy, especially at low or moderate rolling temperature. Four types of rolled AZ31 magnesium alloy sheets were produced by rolling strong basal textured AZ31 plates at 150 ℃ and 300 ℃ respectively through different rolling paths by two passes till total reduction 17%. The rolling paths are normal and cross rolling respectively: the rolling directions of the two passes for normal rolling are mentally paralleled while perpendicular to each other for the cross rolling. Sheets are characterized in terms of microstructure and texture using optical microscope and scanning–electron microscope equipped with EBSD detector, and their mechanical performances are measured by uniaxial tensile tests at room temperature and a strain rate of 0.001 s⁻¹. Tensile samples are cut parallel or perpendicular to the final rolling direction to obtain the mechanical anisotropies. The effects of the {10¯11}–{10¯12} double twins occurred during rolling onto the sheets the microstructure, texture and mechanical properties of the rolled sheets are discussed and related to each other. The results show that proportion of {10¯11}–{10¯12} double twins varies widely in different rolled sheets, which are determined by the rolling temperature. The twins in different rolled sheets are arranged in different ways. In the normal rolled sheets, the traces of twins are approximately perpendicular to the final rolling direction, while in the cross rolled sheets there are both traces of twins parallel and to the final directions. This phenomenon is related to the variant selection of twinning during rolling deformation. And the variant selection law is related to the rolling direction. For the same reason, the textures of twins in the rolled sheets produced through different paths are different. The textures of twins will add onto the bulks, and increases the textural difference between the bulks. The differences between mechanical properties of the rolled sheets are also related to the different textures and microstructures of the sheets caused by twins.

The difference of haemocompatibility of medical 316L stainless steel passivated by nitric acid (NT) and citric acid (CT) was studied. Platelet adhesion and protein adsorption were studied to evaluate the haemocompatibility of the 316L stainless steel passivated by the two different methods. XPS analysis, water contact angle and surface charge measurement were used to analyze the surface properties of the steel such as chemical composition and depth distribution of the main elements in passivated films, surface energy and surface charge. The results showed that the 316L steel passivated by citric acid displayed better haemocompatibility, which could be related to the higher surface energy and relatively lower surface charge. The results also showed that the polar component of surface energy was of linear relation with the albumin adsorption on 316L stainless steel while the surface charge had the same relation with fibrinogen adsorption.

The hot deformation behavior of GH738 superalloy with different initial grain sizes was studied using hot compression experiments via Gleeble–1500. Correlations between flow stress, process parameters and microstructure evolution were characterized in the temperature range of 1000—1160 ℃, strain rate range of 0.01—10 s⁻¹ and engineering strain range of 15%—70%. Besides, metadynamic recrystallization and static recrystallization were studied in the temperature range of 1040—1120 ℃, strain rate range of 0.1—10 s⁻¹ and engineering strain range of 15%—50% with soaking time for 0—45 s; grain growth behavior was researched in the temperature range 980—1140  with soaking time for 0—4 h. The results show that recrystallization behavior of GH738 superalloy was significantly affected by initial grain size, deformation temperature, strain and strain rate. Thermomechanical behavior and microstructural evolution models were systematically constructed based on the investigation of dynamic recrystallization, meta–dynamic recrystallization, static recrystallization and grain growth. The analyses indicate that these models shows a high correlation with actual results of GH738 superalloy.

Microstructure evolution models of dynamic recrystallization, meta–dynamic recrystallization, static recrystallization and grain growth behavior for GH738 superalloy were implanted into finite element software MSC. SUPERFORM with FORTRAN language by means of the user subroutines, in order to add the function of predicting microstructure evolution during hot forging to MSC. SUPERFORM. Microstructure evolution models of GH738 superalloy and the feasibility of the redeveloped MSC.SUPERFORM were verified by comparison between the simulated and experimental results on hot compression specimens and dia.250 mm turbine disc. The numerical simulation of the dia.1250 mm turbine disc forging was carried out by the redeveloped MSC.SUPERFORM, showing that hot working window was in temperature range of 1040—1100  ℃, strain rate range of 10—25 mm/s. Comparison between simulated and actual forging results in the condition of 1080  ℃, 10 mm/s showed that the simulated microstructure was in good agreement with the actual result. Besides, the numerical simulation of the dia.1400 mm turbine disk forging was also carried out by the redeveloped MSC.SUPERFORM. Therefore, the construction of microstructure evolution models of GH738 superalloy and the feasibility of the redeveloped MSC.SUPERFORM are of great significance to accurate control and prediction of turbine disc microstructure.

The introduction of invasive marine species into new environments by the ballast water of ships has been identified as one of the four greatest threats to the world’s oceans. Many technologies have been developed for ballast water treatment among which electrolytic treatment method has been taken as the most promising one. However, the corrosion problem of metals in treated seawater was seriously concerned by international maritime organization (IMO) and ship owners, especially the corrosion of 316L stainless steel which is widely used in the monitoring equipments of the ballast system of ships. In this study, the variation of environmental parameters of the seawater before and after electrolytic treatment was monitored. The corrosion behaviors of 316L stainless steel in both natural and treated seawater were investigated by electrochemical methods such as open–circuit potential (EOCP) measurements, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results showed that the pH value of the seawater increased and the dissolved oxygen content decreased slightly after electrolytic treatment, and the contents of dissolved organic carbon and particulate organic carbon decreased significantly in treated seawater. The corrosion test results showed that the resistance of 316L stainless steel to pitting corrosion was enhanced in treated seawater. Compared to the system in natural seawater, the open–circuit potential of the steel in treated seawater shifted about 0.4 V positively, and charge transfer resistance of the steel greatly increased. The breakdown potential of passivation films in treated seawater positively shifted more than 0.37 V. Our experimental results suggested that the corrosion resistance of 316L stainless steel in treated seawater was improved, which was ascribed to the thickening and compactness of the passivation film formed in treated seawater. It is safe for 316L stainless steel to be used in treated ballast water with the total residual chlorine (TRC) concentration of 9.50 mg/L.

The magnetic properties of commercial 2∶17–type SmCo magnet is low at high temperature, despite good properties at room temperature and its application temperature is usually lower than 300 ℃. In recent years, significant progress has been made on the development of SmCo permanent magnets for high temperature applications. Despite the maximum operating temperature being up to 500 ℃, the magnets were found to have low magnetic properties at room temperature and 350 ℃. Thus, there has been a demand for developing permanent magnet materials with high properties at moderate temperatures below 350 ℃. The effect of Fe and Cu contents on the magnetic properties of Sm(CobalFexCuyZr0.03)7.5 (x=0.16—0.28, y=0.06, 0.08) magnets at room temperature and 350 ℃ have been systematically studied. The results show that with increasing Fe content, the intrinsic coercivity iHc gradually increases, reaching an optimal value of 2473 kA/m, and then drops rapidly at room temperature; the remanence Br rises monotonically with increasing Fe content. The intrinsic coercivity iHc increases with raising Cu at a constant Fe content. The absolute value of temperature coefficient of coercivity |β| rises monotonically with increasing Fe content, and decreases with increasing Cu content. Sm(CobalFe0.20Cu0.08Zr0.03)7.5 alloy is expected for potential applications at moderate temperatures below 350 ℃.