A three-dimensional (3D) numerical analysis model of tungsten inert gas welding arc interacting with an anode material is presented based on the local thermodynamic equilibrium assumption and taking the behavior of metal vapor into account. The thermodynamic parameters and transport coefficients of plasma arc are dependent on the local temperature and metal vapor concentration. A second viscosity approximation is used to express the diffusion coefficient which describes the metal vapor diffuse in the argon plasma. The weld pool dynamic is described by taking into account the buoyancy, Lorentz force, surface tension, and plasma drag force. The temperature coefficient of the surface tension at the weld pool surface is considered in two ways: one is taken as a function of temperature with only oxygen being the active component, and the other is taken as a constant value. The distributions of temperature field and velocity field of arc plasma and weld pool, metal vapor concentration and current density in the arc plasma are investigated by solving the Maxwell equations, continuity equation, momentum conservation equation, energy conservation equation and the components of the transport equation. The influence of metal vapor on arc plasma behavior and that of arc plasma on the weld pool are studied and compared with the non-metal vapor results. It is shown that the distribution of Fe vapor concentrates around the weld pool surface. Metal vapor has obvious shrinkage effect on arc plasma, and weak influences on velocity and potential of the arc plasma. In addition, the metal vapor has a weak effect on the distributions of velocity and shear force on the weld pool surface and no obvious influence on the molten pool shape. We test two different methods to illustrate this point in the case with or without metal vapor. The method used for a variable temperature coefficient of surface tension allows the prediction of a depth-to-width ratio and weld pool shape in agreement with experimental result when taking the behavior of metal vapor into account. The results in this paper, obtained by simulation are in good agreement with experimental results and also with the simulation results by some other authors.

The thermodynamic-related physical parameters, precipitation amount of equilibrium phase, and initial precipitation temperature of Al-(1.9–2.5) Cu-(1.2–1.8) Mg-(0.9–1.5) Fe-(0.9–1.5) Ni alloy were simulated by using the thermodynamic simulation software JMat-Pro. The results show that with the change of element content, the liquidus temperature is in the range of 641.92–638 °C. The precipitation transition temperature of the eutectic phase with a low melting point ranges from 515 °C to 517.25 °C. The solidus temperature is closely related to Cu/Mg. The dendrite spacing decreases with the increase of Mg and Fe (Ni) contents, among which Mg has the greatest influence, followed by Fe (Ni) and Cu. The partial molar Gibbs free energy of Cu, Mg, Fe, and Ni is negative. The activity of Mg increases with the decrease in temperature, and the maximum activity is 0.10189, while the activities of Cu, Fe, and Ni are close to 0. The initial precipitation temperatures of S(Al2CuMg) and Al9FeNi phases are 424–450 °C and 635.4–643.01 °C, respectively. The initial precipitation temperature of the Al9FeNi phase decreases with the increase of Cu and Mg contents, while it increases with the increase of Fe (Ni) contents. With the increase of Cu and Mg contents, the initial precipitation temperature of S(Al2CuMg) increases and decreases with the increase of Fe (Ni) contents. The precipitation amount of S(Al2CuMg) mainly depends on the content and ratio of Cu and Mg, while that of Al9FeNi increases with the increase of Fe and Ni elements in the same proportion.

In order to reveal the law of arc plasma flow and heat transfer in the process of flat tungsten electrode TIG welding as auxiliary heat source for hardfacing of cast iron surface. According to the free burning TIG arc using platy tungsten electrode, A three dimensional (3D) model for tungsten inert gas welding using platy tungsten electrode has been developed. The whole region of platy tungsten TIG arc, namely, platy tungsten cathode, arc plasma and anode surface is treated in a unified numerical model. By using fluent software to do the second development of equations source and solve these equations, the distribution of temperature, velocity and current density are obtained. The simulation results show that the current of flat tungsten electrode is more dispersed, and the heat generation of arc is more dispersed, which leads to the decrease of arc temperature; The current density on the cathode is much higher than that on the anode.