A mathematical energy coupling model was developed to analyze the light transmission in the keyhole and energy distribution on the keyhole wall. The main characteristics of the model include: 1) a prototype of the keyhole and the inverse Bremsstrahlung absorption coefficient in the keyhole plasma are obtained from the experiments; 2) instead of using a parallel incident beam, a focused laser beam with real Gaussian intensity distribution is implemented; 3) both Fresnel absorption and inverse Bremsstrahlung absorption during multiple reflections are considered. The calculation results show that the distribution of absorbed laser intensity by the keyhole wall is not uniform. The maximum laser energy is absorbed by the bottom of the keyhole, although no rays irradiate directly onto the bottom. According to analysis of beam focusing characteristics, the location of the focal plane plays a more important role in the laser energy absorption by the front wall than by the rear wall.

A novel approach based on the quantitative phase field model was proposed to calculate the interface mobility and applied to the α/β interface of a ternary Ti-6Al-4V alloy. Phase field simulations indicate that the higher interface mobility leads to the faster transformation rate, but only a unique value of interface mobility matches the diffusion equation under the diffusion-controlled condition. By comparing the transformation kinetics from phase field simulations with that from classical diffusion equation, the interface mobility at different temperatures can be obtained. The results show that the calculated interface mobility increases with increasing temperature and accords with Arrhenius equation very well.

A first-principles study was reported based on density functional theory of hydrogen vacancy, metal dopants, metal dopant-vacancy complex in LiBH₄, a promising material for hydrogen storage. The formation of H vacancy and metal doping in LiBH₄ is difficult, and their concentrations are low. The presence of one kind of defect is helpful to the formation of other kind of defect. Based on the analysis of electronic structure, the improvement of the dehydrogenating kinetics of LiBH₄ by metal catalysts is due to the weaker bonding of B-H and the new metal-like system, which makes H atom diffuse easily; H vacancy accounts for a trace amount of BH₃ release during the decomposing process of LiBH₄; metal dopant weakens the strength of B-H bonds, which reduces the dehydriding temperature of LiBH₄. The roles of metal and vacancy in the metal dopant-vacancy complex can be added in LiBH₄ system.

An advanced simulation that considers the effect of wire vibrations was proposed for predicting accurately wear profiles of a die used in a wire-drawing process. The effect of wire vibrations, the changes in the wear profiles, and the generation of ringing during die approach were investigated by this simulation. Wire vibrations occurring between the die and the drum are governed by a partial differential equation called the wave equation, which is a function of the wire length, tension, density, and initial wire velocity. The wire-drawing process was simulated by the commercial code Abaqus FEA, and the die wear profiles were predicted by Archard’s wear model. The predicted profiles were compared with measured profiles of a worn drawing die after producing 5 t of AISI 1010 wire; the die was made of tungsten carbide with a Brinell hardness of HB 682. The profiles predicted by considering the effect of wire vibrations are in good agreement with the experimental data, indicating that the advanced simulation can be used to accurately predict the die wear profiles when ringing is observed during die approach.

The arbitrary Lagrangian-Eulerian(ALE) adaptive remeshing technology and the HyperXtrude software of transient finite element simulations were used on analogue simulation of aluminium extrusion processing. The field distributions of strain rate, stress, temperature and velocity of metal flow were obtained. The results are basically consistent with the experiment, which indicates that this method may successfully predict the defects in the actual extrusion process.

To investigate the workpiece curvature influence on groove deformation, numerical studies with curvature varying from negative to positive were conducted on copper material. Groove deformations were analyzed, including groove geometry, effective stress distribution and plough force. The curled groove shape whose workpiece curvature was 0.133 mm^-1 was validated by experiments. Moreover, a series of geometry models with various curvatures were introduced to analyze the change of groove deformation. The results show that positive curvatures influence groove deformation more intensively than negative or zero curvature. It is mainly due to the action of the tool forming face during plough process.

Chlorination roasting followed by water leaching process was used to extract lithium from lepidolite. The microstructure of the lepidolite and roasted materials were characterized by X-ray diffraction (XRD). Various parameters including chlorination roasting temperature, time, type and amount of chlorinating agents were optimized. The conditional experiments indicate that the best mass ratio of lepidolite to NaCl to CaCl₂ is 1:0.6:0.4 during the roasting process. The extraction of lithium reaches peak value of 92.86% at 880 °C, potassium, rubidium, and cesium 88.49%, 93.60% and 93.01%, respectively. The XRD result indicates that the major phases of the product after roasting lepidolite with mixture of chlorinating agents (CaCl₂ and NaCl) are SiO₂, CaF₂, KCl, CaSiO₃, CaAl₂Si₂O₈, NaCl and NaAlSi₃O₈.

The thermodynamic re-assessment of Au-Pt binary system was carried out by using the Calphad method and based on the recent experimental data. The Gibbs energies of face-centred cubic and liquid phases were described by a sub-regular solution model with the Redlich-Kister equation. Much effort was taken to reproduce the phase equilibrium results and thermodynamic properties of the solid phase, including the activity and mixing enthalpy. The constraint of the third law of thermodynamics was also considered in the assessment. According to the presently assessed results, the miscibility gap region in the Au-Pt system slightly shifts to the Au-rich side, and the critical point of the miscibility gap is about 1200 °C and Au-56% Pt.

The structural, electronic and elastic properties of common intermetallic compounds in FeTiCoNiVCrMnCuAl system high entropy alloy were investigated by the first principles calculation. The calculation results of formation enthalpy and cohesive energy show that FeTi, Fe₂Ti, AlCrFe₂, Co₂Ti, AlMn₂V and Mn₂Ti phases may form in the formation process of the alloy. Further studies show that FeTi, Fe₂Ti, AlCrFe₂, Co₂Ti and AlMn₂V phases with higher shear modulus and elastic modulus would be excellent strengthening phases in high entropy alloy and would improve the hardness of the alloy. In addition, the partial density of states was investigated for revealing the bonding mode, and the analyses on the strength of p-d hybridization also reveal the underlying mechanism for the elastic properties of these compounds.

Thin copper sheets as marker material were embedded into weld path of 2024 aluminium alloy plates and their final position after friction stir welding was examined by metallographic techniques. Referring to the visualized material flow patterns, a three-dimensional model was developed to conduct the numerical simulation of the temperature profile and plastic material flow in friction stir welding. The calculated velocity contour of plastic flow in close proximity of the tool is generally consistent with the visualized results. As the tool rotation speed increases at a constant tool travel speed, the material flow near the pin gets stronger. The predicted shape and size of the weld nugget zone match with the experimentally measured ones.

Based on the research on the solidification of twin-roll continuous casting aluminum thin strip, the analytical model of heterogeneous nucleation, the growth kinetics of tip (KGT) and columnar dendrite transformation to equiaxed dendrite (CET) of twin-roll continuous casting aluminum thin strip solidification was established by means of the principle of metal solidification and modern computer emulational technology. Meantime, based on the cellular automaton, the emulational model of twin-roll continuous casting aluminum thin strip solidification was established. The foundation for the emulational simulation of twin-roll casting thin strip solidification structure was laid. Meanwhile, the mathematical simulation feasibility was confirmed by using the solidification process of twin-roll continuous casting aluminum thin strip.

The isothermal compression tests were carried out in the Thermecmastor-Z thermo-simulator at temperatures of 800, 850, 900, 950, 1000 and 1050 °C and the strain rates of 0.01, 0.1, 1 and 10 s^-1. The influence of deformation temperature and strain rate on the flow stress of Ti-6Al-2Zr-1Mo-1V alloy was studied. Based on the experimental data sets, the high temperature deformation behavior of Ti-6Al-2Zr-1Mo-1V alloy was presented using the intelligent method of artificial neural network (ANN). The results indicate that the predicted flow stress values by ANN model is quite consistent with the experimental results, which implies that the artificial neural network is an effective tool for studying the hot deformation behavior of the present alloy. In addition, the development of graphical user interface is implemented using Visual Basic programming language.

Isothermal hot compression tests were carried out on Mg−3.0Nd−0.2Zn−0.4Zr (mass fraction, %, NZ30K) alloy using a Gleeble−3500 thermo-simulation machine at temperatures ranging from 350 to 500 °C and strain rates from 0.001 to 1 s⁻¹. A correction of flow stress for deformation heating at a high strain rate was carried out. Based on the corrected data for deformation heating, a hyperbolic sine constitutive equation was established. The constants in the constitutive equation of the hyperbolic sine form were determined as a function of strain. The flow stresses predicted by the developed equation agree well with the experimental results, which confirms that the developed constitutive equations can be used to predict the flow stress of NZ30K alloy during hot deformation.

Departing from an analytical phase transformation model, a new analytical approach to deduce transformed fraction for non-isothermal phase transformation was developed. In the new approach, the effect of the initial transformation temperature and the accurate “temperature integral” approximations are incorporated to obtain an extended analytical model. Numerical approach demonstrated that the extended analytical model prediction for transformed fraction and transformation rate is in good agreement with the exact numerical calculation. The new model can describe more precisely the kinetic behavior than the original analytical model, especially for transformation with relatively high initial transformation temperature. The kinetic parameters obtained from the new model are more accurate and reasonable than those from the original analytical model.

A continuous semisolid extending extrusion (CSEP) method was proposed. Temperature field and metal flow during continuous semisolid extending extrusion process of 6201 alloy tube were studied. During the process, the temperature in the roll−shoe cavity decreases gradually, and the isothermal lines of the alloy deviate from the shoe side to the work roll side in the roll-shoe gap. Metal flow velocity decreases gradually from the surface of the work roll to the surface of the shoe. In the extrusion mould, alloy temperature decreases gradually from the entrance to the exit and from the center to the sidewall of the mould. The extending cavity is radially filled with the alloy. The flow lines in the tube corresponding to the centers of the splitflow orifices and the welding gaps are dense, and the corresponding harness values are high; there are 8 transitional bands between them. In order to prepare 6201 alloy tubes with good surface quality, the pouring temperature from 750 °C to 780 °C was suggested.

Comprehensively considering energy, volume and electronic structure of alloys, the ninth equation was determined as the interaction function of Nb−Mo alloys system in BCC structure on the basis of idea of systematic science of alloys, experimental lattice constants and heats of formation of disordered Nb_(1−x)Mo_x alloys. The structural parameters and properties of Nb and Mo characteristic atoms sequences and corresponding characteristic crystals sequences were determined in Nb−Mo alloys system. The electronic structure and physical properties of disordered Nb_(1−x)Mo_x alloys system were calculated according to concentration of characteristic atoms of disordered alloys. The change trend of physical properties is the same as that of electronic structure.

The electronic structures, chemical bonding and elastic properties of the tetragonal phase BiOCuS were investigated by using density-functional theory (DFT) within generalized gradient approximation (GGA). The calculated energy band structures show that the tetragonal phase BiOCuS is an indirect semiconductor with the calculated band gap of about 0.503 eV. The density of states (DOS) and the partial density of states (PDOS) calculations show that the DOS near the Fermi level is mainly from the Cu-3d state. Population analysis suggests that the chemical bonding in BiOCuS has predominantly ionic character with mixed covalent−ionic character. Basic physical properties, such as lattice constant, bulk modulus, shear modulus, elastic constants, were calculated. The elastic modulus and Poisson ratio were also predicted. The results show that tetragonal phase BiOCuS is mechanically stable and behaves in a ductile manner.