Advanced Materials Research Vols. 399-401

Abstract: A physical model of magnetron sputtering process was built, the distribution of film thickness on the substrate was deduced, and the data were analysised by using the Mathematica and Matlab. The results show that the distribution of the film thickness on the substrate is uneven and it is also influenced by the radius as well as the distance between the target and substrate. The results of experiment correspond fairly well with the theory. The relational expression provides a theoretical basis for evaluation and estimation of the film thickness.

Abstract: The microstructures and the solidification processes simulation of multi-principal high-entropy alloy FeCoNiCrMn were studied by using both experimental and computational approaches. The microstructures were identified by methods of XRD, SEM and EDS. The solidification process was simulated by Scheil-Gulliver solidification model. The alloy mainly forms a single FCC solid solution, but Mn atoms, as well as Ni atoms tend to be enriched in residual liquid phase during the solidification process. These atoms show interdendritic segregation. Present experimental results and computational results are supported each other well.

Abstract: Based on the research on the solidification of twin-roll continuous casting aluminum alloy thin strip, the analytical model of heterogeneous nucleation, the growth kinetics of tip (KGT) of twin-roll continuous casting aluminum alloy thin strip solidification are established by means of the principle of metal solidification, meantime based on the cellular automaton, the emulational model of twin-roll continuous casting aluminum alloy thin strip solidification is established. The foundation for the emulational simulation of twin-roll continuous casting thin strip solidification structure is laid. Meanwhile has confirmed the mathematical simulation feasibility by using the solidification process of twin-roll continuous casting aluminum alloy Thin Strip.

Abstract: Corrosion perforation in the oil-tank bottom is one of the most damaging mechanisms in oil-tanks. This paper presents a two-dimentional cellular automata model which simulates the corrosion perforation in the oil-tank bottom. According to the mechanism of metal corrosion in the oil-tank bottom, the CA model which simulates the electrochemical reactions and diffusion steps of pitting corrosion is proposed. With a series of simulation, the results show that CA is a powerful approach to model corrosion perforation in the oil-tank bottom, which could be of practical importance in predicting the security of oil-tanks.

Abstract: Computer controlled optical surfacing (CCOS) is widely used in aspheric optical lenses fabrication because of their high convergence rate on surface based on deterministic removal processes since 1963. As an important part of CCOS techniques, reasonable tool-path would increase the polishing speed, decrease the processing time and then improve the efficiency of polishing. Optimized policy combined with improved Prim algorithm is presented in this paper based on the study of the characteristic of aspheric polishing and the tool-paths in common use. The simulated results show that the length of tool-path is reduced so as to decrease the processing time and increase the working efficiency.

Abstract: A three-dimensional phase field model applicable for the B2-B19′ martensitic phase transformation of NiTi alloys was developed to predict the twinning modes in the B2-B19′ transition. The phase field simulation results showed that by taking into account the transformation induced elastic strain, the martensite variants were self-accommodated and sheared along the specific interface in the entire transition stage for reducing the elastic energy, whether the formed interface between the variants belongs to twinning plane could be determined by calculating the minimum value of long range elastic interaction energy, Bpq. Through comparison with the existing analytical solutions, it is demonstrated that the phase field model can be used to predict the type I twinning modes in the B2-B19′ phase transition with good precision.

Abstract: Physical simulation model of γ_Fe → α_Fe grain nucleation & growth in isothermal solid-state transformation and the rule of grain nucleation & grain growth’s boundary migration are established. The Genetic Algorithm is introduced in the process of grain nucleation & growth. The grain boundary migration agrees with the theory of grain growth. The system free energy ΔG calculation formula is exported. The thermodynamic criterion of new nucleus growing up is that new grain average radius r_c is bigger than theory critical average radius r_c0 when ΔG is achieved ΔG_max, ΔG is continually decreased at the remaining transformation, the final energy ΔG_f is less than initial energy at the end of transformation; be influenced by the limit of nucleation number N.

Abstract: The FE model of the pretightening assembly moving beam of open-die forging hydraulic press is built with FE simulation software ABAQUS in the study. With the FE model, the force status of pretightening assembly moving beam is studied. Then the pretightening force of assembly moving beam is further studied and the computing method of pretightening force is given. The main achievements of the study include: Under pretightening, the stress of main moving beam is very low and that of guild sleeves is also lower than the allowable stress. Under center loading, the stress of the center field of main moving beam is higher and that of guild sleeves is almost same to that of pretightening. Under eccentric loading, the stress of same deviation field of main moving beam is higher and the effect of pretightening force on the stress of main moving beam is very small. The stress distribution of guild sleeves with different pretightening force is same and the effect of pretightening force on its strength is very low. The pretightening force of tension rod can be computed with the force of press, the allowable eccentric value of the workpiece, the distance between up guild section and down guild section of guild sleeve and the quantity of tension rods. The results of the study are very useful to design and install the pretightening assembly moving beam of open-die forging hydraulic press.

Abstract: A multi-state free energy function for deformation alloy with storage energy is proposed to simulate the microstructure evolution of static recrystallization with phase field model. The grain growth and grain size distribution during recrystallization are discussed. The simulation results are in good agreement with other theoretical or experimental results.

Abstract: The crystal structure, electronic structure and ferromagnetic properties of the transition metals M (where M=Co, Ag) doped rutile TiO₂ are studied by using first-principles calculations based on the density functional theory (DFT) and projector augmented wave (PAW) pseudo-potentials (PP) method. In the doped system M₂Ti₁₄O₃₂, the two doping atoms tend to align along c axis in the stablest configuration state. When M represents Co atom, the ferromagnetic state is favorable with magnetic moments of 0.99μB per Co atom, while Ag₂Ti₁₄O₃₂ has no magnetic moment. Doping atoms induce new energy level, which reduces band gap, decreases Fermi energy level and thus considerably affects the optical absorption and photocatalytic activities of TiO₂ under visible light irradiation.