Based on the thermodynamic analysis on the selective oxidation of the main elements in the new generation of clean steel production process, and the production practices of hot metal treatment in the new process of clean steel production accumulated by the Jing Tang Iron and Steel Corporation, the control of the main elements such as S, P, C, etal., were investigated, and the main characteristics of the new generation of clean steel production process were analyzed. We indicate that several production problems must be solved. The research results show that, by using KR desulphurization technology, the S content of hot metal can be steadily controlled to less than 0.0020%. The final S control of the new production process of clean steel depends mainly on the resulfurization content in the dephosphorization furnace. Increasing the slag basicity and reducing the content of S from scrap and slag forming materials can reduce the resulfurization of hot metal. The formation of proper slag basicity at relatively lower hot metal pretreatment temperature (1300-1350 ℃) and at relatively higher oxygen potential is the key to solving the problem of removing P at high C content. The P content in dephosphorization furnace, when producing common low P steel (P<0.006%), may be controlled at less than 0.03%, whereas the P content should be below 0.008% when producing ultra low P steel (P<0.002%). Less-slag smelting, lower Fe losing and high carbon tapping of decarburization furnace are the important technological characteristics of the new generation of clean steel production process.

The Tb_0.3Dy_0.7Fe_1.95-xTi_x ($x$=0, 0.03, 0.06, 0.09) alloys were prepared by high--vacuum non-consumable arc melting furnace. The crystal structure, microstructure, magnetostriction and their relationships of the Tb_0.3Dy_0.7Fe_1.95-xTi_x ($x$=0, 0.03, 0.06, 0.09) alloys were systematically studied. The results demonstrated that the matrix phase of the Tb_0.3Dy_0.7Fe_1.95-xTi_x (x=0.03, 0.06, 0.09) alloys consisted predominantly of the Laves phase with MgCu₂ structure. After Ti addition, the lattice parameter of the Laves phase in the alloys was decreased by substituting rare earth elements Tb and Dy, and the formation of the TiFe₂ phase as the primary phase made the solidifying liquid become rich in rare earths and suppressed the formation of the deleterious RFe₃ (R=Tb and Dy) phase. Ti was found to be soluble in the matrix RFe₂ and R-rich phases and formed the matrix (R, Ti)Fe₂ and (R, Ti)-rich phases. The concentration of Ti affected the magnetostriction significantly. The improvement in magnetostriction was maximum for the Ti-added alloys with a low concentration of the Ti (x=0.03) as compared to the parent alloy Tb_0.3Dy_0.7Fe_1.95. However, the decrease in magnetostriction at a higher concentration (x=0.09) was due to the formation of paramagnetic phases TiFe₂ and (R, Ti)-rich. Whereas the magnetostriction had little improvement as compared to the parent alloy\linebreak Tb_0.3Dy_0.7Fe_1.95.

In comparison with the conventional grain-oriented electrical steels (the so-called CGO steels), the high permeability electrical steels (the so-called Hi-B steels) including those of nitrided steels possess higher magnetic properties, but their processing window is narrow. In particular, a near brass--oriented texture which rotated around the normal direction of sheets from Goss orientation is often observed in improperly processed sheets of Hi-B steels, i.e, this type of sheet possesses a correct morphological structure of well abnormally grown grains, but a poor crystallographic texture with low magnetic properties. The underlying mechanism is less dealt with in literature in comparison with the formation of Goss texture. Thus, the objective of this work is to analyze the formation mechanism of this texture component. For this purpose, XRD and EBSD technique were applied to reveal both macro- and micro-textures from the shear texture of hot rolled plate surface to primarily and secondarily annealed sheets paying particular attention to the origin and relationship of Brass-oriented grains with their surrounding grains. It is demonstrated that Brass-oriented grains are formed by the rotation of Goss-oriented grains around the normal direction in the sheared surface layer of hot rolled plate when the shearing around transverse direction is restrained. Compared with the close relation between Goss and {111}<112> oriented grains, similar behaviors during cold rolling and annealing occur between brass-- and {111}<110>-oriented grains, namely, the latter are also inclined to be adjacently related and mutual transformation could occur between those deformation grains and recrystallization grains. In particular, a higher rolling reduction reduces Goss grain number much significantly, whereas it favors the retention of brass- and {111}<110>-oriented grains leading to preferred growth of brass-oriented grains. In the condition of easy growth of Brass grains with their {110} being parallel to rolling plane like Goss grains in the thinner sheets, the much fewer Goss grains could not swallow the brass-oriented grains. Thus, this technical issue of producing grain oriented electrical steels with high magnetic properties can be understood in terms of fundamentals of texture evolution during deformation and recrystallization of bcc metals.

Unsteady turbulent flow in the thin slab continuous casting mold has been computed using the large eddy simulations (LES). The cassette filter function is used to deal with unsteady Navier-Stokes equation, and the Smagorinsky-Lilly sub-grid scale model is used to calculate the dissipative effort of the unresolved small eddies. And this LES model has been validated with the measurements of the particle image velocimetry (PIV) and the ultrasonic flaw detection. The computational domain includes the entire submerged entry nozzle (SEN) starting from the tundish exit and the extended mold region. The results show the characteristics of the unsteady turbulent flow in the thin slab continuous casting processes, such as the vortices distribution and the formation, development, shedding and fracture process of the large eddy coherent structures. The simulation also shows that the turbulent flow is asymmetric even if the nozzle and mold is perfect symmetric in geometry. The flow deviation of the molten steel in the mold is inevitable existence. And the interactions of flows in two sides of nozzle also can cause intensity velocity fluctuation near the meniscus. With the development of the unsteady turbulent flow, the flow deviation of the molten steel in the thin continuous casting strand presented periodic change, and the period is about 40 s.

Three-dimensional (3D) microstructures can clearly reveal the size, shape and distribution of the phases, providing a novel way to deeply understand the formation mechanism of the solidified phases. In this paper, by using the serial sectioning technique, the 3D microstructure of the primary Al₂Cu phase was reconstructed and the eutectic spacing adjustment was investigated during directional solidification of Al-40%Cu hypereutectic alloy. The results show that the primary Al₂Cu phase pattern was observed faceting due to the growing faceted angle and plane parallel to the solidification direction at the pulling rate of 5 μm/s. Further, there existed some hopper-like cavities in the 3D microstructure of the primary Al₂Cu phase that caused by remelting owing to a large amount of the latent heat difficult to be extracted from the solidification interface. For the 3D eutectic microstructures of the Al-40%Cu alloy, the growth direction of the Al and Al₂Cu phases in the coupled eutectics had a deviation angle of 5.1^o with the heat flux direction and the phase volume fractions of the  Al and Al₂Cu phases were measured directly to be 56.8% and 43.2%, respectively. In addition, at the abrupt change in pulling rate from 2 μm/s to 500 μm/s, the lamellar-to-rod eutectic transition was observed and the continuously splitting and branching occurred in different planes responsible for the eutectic spacing adjustment in the 3D microstructure of the Al-40%Cu alloy. Meanwhile the renuleation mechanism in the 2D microstructure for the adjustment of the eutectic spacing did not work in the 3D eutectic microstructure of the Al-40%Cu alloy.

Eutectic microstructures are one of the most common solidification patterns in the binary or
multi-component alloy systems. Due to the fine periodic microstructures of the eutectic alloys, the commercial
applications of the eutectic alloys can improve the mechanical properties of the castings. The solidification
mechanism of eutectic alloys has been widely studied by a lot of experimental works and theoretical analysis over
the years. Recently, numerical models were used to study the mechanisms of formation of phase patterns and
selection dynamics of the lamellar eutectic, such as phase field (PF) and cellular automaton (CA) model, which
can promote the development of eutectic growth theory. Based on the existing CA method for
binary primary α phase, a modified cellular automaton (MCA) model was developed for the simulation of binary
eutectic growth. In this model, the influence of constitutional and curvature undercooling on the interface
morphology was considered. The growth rate of eutectic interface was calculated by the solute conservation at the
$\alpha$/liquid and $\beta$/liquid interfaces. The model could simulate the phenomenon of overgrowth, splitting and
steady state growth of the eutectic lamellar. CBr₄-C₂Cl₆ eutectic transparent alloy was chosen to validate the model. The simulated results showed that the
increasing pulling rate lead to a smaller eutectic lamellar spacing, which had a
good agreement with the Jackson--Hunt theory and the experimental results from the literature. Eutectic
morphology evolution was simulated under a constant pulling rate and temperature gradient, which showed that
the stable lamellar structures existed when the initial lamellar spacing was in a finite range between the minimum
stable spacing λ_m and the limiting maximum stable spacing λ_m. A smaller initial lamellar
spacing would lead to lamellar annihilation. Conversely, a larger initial lamellar spacing could lead to the lamellar
nucleation due to the appearance of solute rich concave at the center of the α/liquid interface. Meanwhile,
the oscillatory instability of
the eutectic lamellar was also reappeared by the MCA model. The MCA model was easily extended to 3D, and
the lamellar-rod transition during directional solidification was simulated, which showed that the ratio of volume
fraction of α and β phase was smaller than 1/Π tend to form lamellar-rod transition
when the initial lamellar spacing was smaller than λ_m.

In traditional aeroengine manufacturing industry, the variation and mechanism of the mechanical property of superalloy used for rotating parts under the actual dynamic load is not given full considerations during its structure design. The mechanical property and deformation behavior of the alloys under the dynamic load have significant difference compared with that under the static load, and therefore the study on the deformation behavior of the alloy under the dynamic load is important for the safety of rotating parts used under the severe service conditions. The effect of microstructural changes of long-term aging GH4169 alloy on the mechanical properties through tensile testing at strain rates ranging from 10¹ to 10³ s^-1 was examined in this paper. The tensile deformation behavior of the alloy and the mechanisms were also discussed. The results showed that the strength of the alloy depends strongly on the aging time, the fracture elongation decreases with the increasing aging time and remains unchanged when aged for 500 h when tensile tested at the strain rates ranging from 10¹ to 10³ s^-1. And when the strain rate is high up to 10³ s^-1, the elongation depends strongly on the aging time and the degradation of ductility by the long-term aging happens ahead of time, but the aging time has no obvious effect on the strength of the alloy. Through tensile testing at the strain rate of 10³ s^-1, it is too late to release the blocked dislocation motion in the way of dislocation decomposition or climb in the alloy. And there is no peaking size effect of the strengthening phase in the alloy with the aging time ranging from 0 to 1000 h and there is no obvious effect of the aging time on the strength of the alloy. The ability of accommodation of plastic deformation by grain boundaries reduces under the dynamic loads due to the existence of precipitate free zones around δ phase at the grain boundary in the alloy by long-term aging, and thus the ductility of the alloy by aging for a shorter time decreases rapidly when tensile tested at the strain rate of 10³ s^-1.

The low temperature superelastic alloys are of wide range of applications, such as to make the energy storage devices, the earthquake protective devices and the abrasion parts, etc. The shape memory alloy (SMA) Ti-50.8Ni-0.3Cr (atomic fraction, \%) is a good low temperature superelastic alloy with low martensitic transformation temperature and high critical stress for inducing martensitic transformation. So far, the effects of the annealing and aging processes on the transformation behaviors of Ti-50.8Ni-0.3Cr SMA, and the characteristics of the shape memory effect, the superelasticity and the stress-strain cycle for annealed Ti-50.8Ni-0.3Cr SMA have been studied, systematically, while the microstructure and deformation characteristics of aged Ti-50.8Ni-0.3Cr SMA were not studied yet. In this paper, the influences of aging processes on the microstructure and superelasticity in Ti-50.8Ni-0.3Cr SMA were investigated using TEM and tensile test. With increasing aging time (t_ag), the morphology of Ti₃Ni₄ precipitate shows fine particle-shape in 300 ℃ aged Ti-50.8Ni-0.3Cr SMA, the morphology of Ti₃Ni₄ precipitate changes from the fine particle-shape to the needle-shape in 400 ℃ aged alloy, and the morphology of Ti₃Ni₄ precipitate  changes from the needle-shape to the plate-shape in 500 ℃ aged alloy. The effect of aging temperature on the precipitate morphology is more outstanding than that of aging time. With increasing t_ag, the tensile strengths (σ_b) in 300 and 400 ℃ aged alloys are increase first and then tend to stable, while σ_b (500 ℃) is decrease first and then tend to stable, and σ_b(400 ℃)>σ_b(300 ℃)>σ_b(500 ℃). The superelasticities of 300 and 400 ℃ aged alloys are better than that of 500 ℃ aged alloy. With increasing t_ag, the critical stress for inducing martensitic transformation of Ti-50.8Ni-0.3Cr SMA is decrease, the superelasticity energy dissipation (ΔW) of 300 ℃ aged alloy is decrease, the $\Delta W$ of 400 ℃ aged alloy is increase, and the ΔW of 500 ℃ aged alloy is increase first and then decrease.

When smelting magnesium alloy under the protected conditions, it is unavoidable completely for magnesium alloy melt to react with the atmosphere, that the loose reaction products are separated very difficultly from the alloy melt. Finally, they become the inclusions in the alloy, to deteriorate the mechanical properties and performance. In this paper, in order to evaluate the inclusions in the new-style Mg-Gd-Y-Zr alloy and find an effective method of eliminating inclusions, the morphology, size distribution, species of inclusions and their formation in the alloy smelting and casting conventionally under gas coverage are analyzed. The settling behavior of the inclusions is also analyzed by the calculations. There are complex inclusion mainly composed of Mg or Y oxide and flux inclusion with spherical, cluster, irregular and linear shape in the Mg-Gd-Y-Zr alloy. The average size and volume fraction of them are 12.7 µm and 0.26%, respectively. The frequency of the inclusions dramatically decreases with their size increasing. The volume of inclusions less than 20 µm occupies nearly 85% of the total volume of inclusions, while the percentage of inclusions less than\linebreak 45 µm is 96%. The calculations show that the settling velocity of inclusions is dependent on their size and density, and increasing the inclusion density can diminish the maximal size of the inclusions in the magnesium alloy, which the maximal size by the calculations is consistent with the experimental result.

Zn addition to the magnesium alloys could result in the age-hardening, and the age-hardening response of Mg-Zn alloys could be further enhanced by the ternary addition of Ca. In order to better understand the mechanism of the Mg-Zn-Ca base alloy design, the solubility of Mg-based< solid solution and relative phase equilibrium at 400 ℃ in low-Ca side of the Mg-Zn-Ca system have been investigated by SEM, EPMA, XRD and DSC. It has been shown that T₁ and T₂ are still main ternary compounds in the Mg-rich corner at 400 ℃ with the addition of Ca to Mg-Zn system, but only T₁ phase could be in equilibrium with the Mg-based solid solution, and the two-phase field of α-Mg+T₁ becomes narrow. The liquid phase with the Ca content less than 8.4\% (atomic fraction) exists in the low-Ca side at 400 ℃, which could be in equilibrium with α-Mg. But liquid phase could not exist in the Mg-Zn-Ca α-Mg+Mg₂Ca+T₁, α-Mg+T₁+Liq, Liq+T₁+T₂ and Liq+T₂+Mg₂Zn₃ in the Mg-Zn-Ca system, respectively.

Titanium and its alloy have been widely used in medical applications owing to their light weight, low elastic modulus, good corrosion resistance and biocompatibility. A new multifunctional β-type titanium alloy Ti-24Nb-4Zr-8Sn has been developed recently for intention of biomedical applications. In comparison with the previously reported alloys, it possesses better biomechanical properties of high strength and low elastic modulus. Since corrosion resistance of biomaterials in human body environment plays important role on bio-safety, it is crucial to evaluate their corrosion behavior in simulated body fluid (SBF). In this paper, the electrochemical corrosion behavior of Ti-24Nb-4Zr-8Sn alloy was investigated in Hanks solution at 37 ℃ by utilizing potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques while XPS, XRD and SEM were employed to analyze the surface morphology, composition and phase constituent. Both commercially  pure titanium (CP-Ti) and Ti-6Al-4V alloy were also investigated to make a comparison. Ti-24Nb-4Zr-8Sn alloy has equiaxed microstructure with the averaged grain size about 200 $\mu$m. In Hanks solution, it exhibits a typical active-passive characterization by the formation of a protective passive film. XPS analyses revealed the passive film mainly consisting of TiO₂, Nb₂O₅ and a little quantity of ZrO₂ and SnO₂. Since the formation of Nb⁵⁺ cations that locate in the crystal lattice of titanium oxide, can cause a decrease in the concentration of defects in the passive film and makes it more stoichiometric and stable, Ti-24Nb-4Zr-8Sn alloy presents much wider passivation region than CP-Ti and Ti-6Al-4V alloy, and its corrosion current density is only 0.049 µA/cm² which is equal to that of CP-Ti. The EIS results indicated the presence of a double layer passive film with a porous outer layer and a dense inner one on the surface of Ti-24Nb-4Zr-8Sn alloy. The resistance of the dense inner layer can reach to the order of 10⁶ Ω·cm², which is much higher than that of the porous outer layer. This indicates that the corrosion resistance of Ti-24Nb-4Zr-8Sn alloy is determined mainly by the dense inner layer. With the immersion time increasing, the inner barrier layer became thicker and its resistance increased, resulting in the improvement of corrosion resistance. The study also found that some of the micro-defects formed in the outer porous layer changed to macro cracks and caused a rapid breakaway of the porous layer due to the binding force between two layers decreasing.

As a kind of clean, efficient and relatively safe energy, nuclear energy has been widely used around the world. The high-level radioactive waste generated in the nuclear has also become a major risk, so the disposal safety of high-level radioactive waste will be especially important. The strategy for disposal of high-level radioactive waste in China is to enclose the spent nuclear fuel in sealed metal canisters which are embedded in bentonite clay hundreds meters down in the bed-rock. The choice of container material depends largely on the redox conditions and the aqueous environment of the repository. One of the choices for the fabrication of waste canisters is Cu, because it is thermodynamically stable under the saline, anoxic conditions over the large majority of the container lifetime. For this advantage, some other countries (Canada, Sweden) have selected Cu as the material of nuclear waste container. However, in the early aerobic phase of the geological disposal the corrosion of Cu could take place, and the corrosion behavior of Cu would be influenced by the complex chemical conditions of groundwater markedly. Pitting corrosion of Cu often take place in power plants or air--conditioning condensate water. The corrosion environment usually contains HCO₃^-, SO₄^2- and Cl^- ions. In the early stage of geological disposal, if the aerobic water with HCO₃^-, SO₄^2-and Cl^- immersion repository, the pitting corrosion of Cu may occur. The content of HCO₃^- and SO₄^2- in the water chemistry environment, as well as the synergy between them, could affect the behavior of pitting seriously. In this work, the cycle polarization behavior and surface morphology of pitting has been investigated in HCO₃^- and SO₄^2- mixed solution, respectively by electrochemical cyclic polarization test and SEM. The results showed that the pitting corrosion behavior of Cu can be divided into the type of active dissolve and the type of film rupture; SO₄^2- could increase Cu pitting sensitivity in both of the two types pitting corrosion. Due to synergies with the SO₄^2-, HCO₃^- could increase the pitting susceptibility first and then reduce the law. In passive film rupture pitting system, SO₄^2- could improve the ability of induce pitting; HCO₃^- could reduce the ability of induce pitting. There is no significant impact on pitting self--healing capacity by the two ions.

Super-hydrophobic surface has been considered a new and promising anti-corrosion technology, recently. A super-hydrophobic film has been fabricated on Cu-Ni alloy (B30) substrates by chemical etching and self-assembly. The effects of etching process and self-assembly technology on the property of filmed B30 had been investigated by means of contact angle measurement and electrochemical test. The results show that suitable surface roughness played a vital role in preparing super-hydrophobic surface with excellent corrosion resistance in comparison with the electrochemical test results of different hydrophobic B30 surface. Moreover, the results indicated that the corrosion resistance of B30 in 3.5%NaCl solution could greatly improved by the super-hydrophobic surface (contact angle 152.8^o), and the inhibition efficiency reached 96.1%.

Composite metastable Ti_0.3Al_0.7N and Ti_0.39Al_0.55Si_0.05Y_0.01NN hard coatings were deposited on a wrought martensite steel 1Cr11Ni2W2MoV for aero-engine compressor blades by the magnetron sputtering system with the bias voltage of 0 and -100 V respectively. Detailed microstructure, chemical composition, crystal structure, hardness and adhesion were examined by means of FESEM, EDS, XRD, Micro hardness tester and scratch tester. The influence of doping with Si and Y and bias on structure, oxidation-resistance and mechanical properties of (Ti, Al)N coatings were investigated. Pulsed bias and the doping with Si and Y gave rise to the change of phase structure and improvement of density. Doping with small amounts of Si and Y into (Ti, Al)N significantly improved the oxidation resistance at 950 ℃. The oxidation-resistance of (Ti, Al, Si, Y)N is based on the formation of dense protective Al₂O₃ layer. The application of negative pulse led to decreased hardness for (Ti, Al)N while remarkable decrease of hardness for (Ti, Al, Si, Y)N. For (Ti, Al, Si, Y)N prepared under -100 V\linebreak bias, annealing 10 h at 950 ℃ slightly decreased it's hardness because of the formation of B4 structure. And for which deposited at 0 V bias, heat-treatment of 950 ℃ for 10 h improved the hardness from 26 GPa to 35 GPa. The hardness change of the coating may be ascribed the transition of B1 phase structure. Scratch tests show that the continuous spall is not occurred for all the coatings under the critical load of 50 N.

Zirconium-based alloys are being used as fuel cladding and structural materials for nuclear reactors since they have a good irradiation stability, corrosion resistance and acceptable mechanical properties in a reactor environment. Recently, more advanced zirconium-based alloys are required for enhanced operating conditions such as an increased burn-up and higher operation temperatures. Therefore, the development of advanced zirconium alloys for a fuel cladding is being progressed in various countries. Among the developed new zirconium alloys, a low Nb containing alloy series designed by China is a group of promising cladding material. For the new alloy system, optimum manufacturing processes are significant factors to improve properties and need urgently to be established. In this work, electron channeling contrast (ECC), secondary electron (SE) imaging and energy dispersive spectroscopy (EDS) analyzing techniques are employed to investigate the effect of pre-deformation following β-quenching on recrystallization and precipitating behavior of a new Zr-Sn-Nb alloy during aging. The results show that remarkable differences exist between the microstructure of specimens with and without pre-deformation prior to aging at the same temperature (650 ℃). Specimens aged without pre-deformation present extremely heterogeneous recrystallized grains that generally own irregular shape. The size discrepancy between the intragranularly fine Zr(Fe, Cr, Nb)₂ precipitates and the larger ones, which is Cu-containing Zr₃Fe particles and distribute along the conserved prior $\beta$ grain boundaries, are distinct. While for specimens aged following 20% pre-deformation, the recrystallized α-grains are evidently fined and homogenized. The size discrepancy between the two sorts of precipitates decrease as well and the larger ones change to distribute along recrystallized α-grain boundaries. Therefore, the introduction of pre-deformation is able to change markedly the characteristics of microstructure and second phase particles distribution and further be utilized to obtain preferred microstructure.

The corrosion resistance of water cooled rebar is improved by applying a chemical reagent cooling process on the basis of maintaining the high mechanical property. To provide the reference basis for the on-site application of chemical reagent cooling process, the temperature field of the two-stage cooling process (first stage of chemical reagent of FM cooling and second stage of water cooling) of rebar produced by chemical cooling is simulated using the finite element method. Furthermore, the corrosion resistance of scale formed during the first stage of chemical reagent cooling was evaluated in laboratory. Applying the processing parameters of water cooling in steel mill, the temperature field of one-stage cooling was simulated. Compared with the temperature field of the one-stage cooling, the influence of processing parameters on the temperature field during two-stage cooling is analyzed. The results showed that the smaller heat transfer coefficient is applied to increase the oxidation temperature and improve the quality of the oxide scale in the first stage of FM cooling. In the second stage of water cooling, the cooling curve is very approximate to that of one-stage cooling when the heat transfer coefficient of one-stage cooling is remained. Therefore, the mechanical property of hot-rolled rebar of grade III can be ensured. Furthermore, the first stage of FM cooling process was implemented in lab using the optimizing parameters obtained from finite element analysis. The oxide scale forming using FM cooling is compact. And its corrosion resistance is much better than water-cooled rebar, which proves that it is feasible to improve the corrosion resistance of water-cooled rebar using FM cooling before water cooling.

There exists obvious deficiency in traditional twining induced plasticity (TWIP) steel which exhibits excessive ductility but rather low strength. In order to improve the property, new composition of a test steel, i.e., Fe-18Mn-0.528Si-0.6C (mass fraction, %) steel is designed through increasing C content and decreasing Mn content upon the estimation result of stack fault energy and phase diagram calculation. That the γ→ε transformation may happen during deformation at room temperature in the designed steel is predicted through calculation. The microstructure, before and after tensile test, of the hot rolling test steel is analyzed with OM, XRD and TEM. It is shown that there occurs simultaneously TWIP and transformation induced plasticity (TRIP) effect in the steel treated by a special hot rolling process (rolling starting temperature 1100 ℃, finishing rolling temperature 850 ℃\linebreak and air cooling) and superior mechanical property with strength higher than 1 GPa and elongation rate higher than 60\% are then obtained which fit very well with the requirement of the third generation automobile steel. It is also revealed the existence of ε martensite obtained through quenching or induced by stress would damage the mechanical property.