Numerical Simulation of Layered Bimetallic ZChSnSb8Cu4/Steel TIG-MIG Hybrid Welding Based on Simufact.

Considering the problem of the weak bonding interface structure between the rolling mill oil and film bearing bushings of Babbitt alloy and steel substrate, a numerical simulation of the layered bimetallic ZChSnSb8Cu4/steel by tungsten inert gas (TIG)-metal inert gas (MIG) hybrid welding process was carried out using Simufact Welding software (version 2020). In this study, the TIG-MIG hybrid welding process was simulated to obtain the temperature field and the stress field distributions. The residual stress and the deformation of the weldment were also analyzed using the calculated results. The results showed that the temperature gradient and the thermal stress were reduced in TIG-MIG hybrid welding compared to the conventional MIG welding preparation of layered bimetal ZChSnSb8Cu4/steel, which resulted in an improvement in the structural stability of the weldment. The temperature field and deformation of TIG-MIG hybrid welding of Babbitt alloy were studied under different controlled electrode spacings and TIG welding currents, and it was found that as electrode spacing increased, so did heat loss. Furthermore, with increased TIG welding current, compressive stress increased and tensile stress at the weld decreased, and the maximum thermal efficiency of welding was with a preheating current of 60 A.

Investigation on the Interface Morphology of Mg/Al Corrugated Composite Plate in the Straightening Process.

The Mg/Al composite plate was developed in aerospace and other fields. At present, through the corrugated rolling method, the bonding strength of Mg/Al composite plate could be increased and the warpage could be reduced. However, this still requires the straightening process to reach the parameters' range. In this work, the original interface morphology of Mg/Al corrugated composite plate was obtained by experimental characterization. Based on the principle of elastoplastic mechanics, the equations of straightener parameters and straightening process parameters were obtained and the influencing factors were deduced. So, the straightening model was established in an Abaqus. The effects of straightener parameters and straightening process parameters on the interface morphology were analyzed and the interface morphology was expressed by amplitude and period length of the equation. The results showed that bending moment, shear strength and the reduction of second roll played roles on the interface morphology. After the first straightening unit, the amplitude increased by 1.1% and the period length increased by 3%. Finally, a complete straightening parameter was designed, which included straightener parameters, straightening process parameters and straightening temperature. The aim of this work was to provide a theoretical basis for establishing a high precision Mg/Al corrugated composite plate straightening model, which could improve the bonding strength while ensuring the straightening effect.

Molecular dynamics study on the relationship between phase transition mechanism and loading direction of AZ31.

To develop and design mg-based nanoalloys with excellent properties, it is necessary to explore the forming process. In this paper, to explore the effect of different loading directions on the phase transformation of magnesium alloy, the model of AZ31 magnesium alloy was established, the process of Uniaxial Compression (UC) of magnesium alloy in different directions was simulated, the changes of atomic position and phase structure were observed, and the phase transformation mechanism of AZ31 magnesium alloy under uniaxial compression under different loading directions was summarized. The conclusions are as follows: the stress and strain, potential energy and volume change, void evolution, phase structure change and dislocation evolution of magnesium alloy are consistent, and there is no significant difference. In the process of uniaxial compression, the phase transformation of hexagonal closely packed (HCP) → face-centered cubic (FCC) is the main, and its structure evolves into HCP → Other → FCC. Shockley partial dislocations always precede FCC stacking faults by about 4.5%, and Shockley partial dislocations surround FCC stacking faults. In this paper, the phase transformation mechanism of AZ31 magnesium alloy under uniaxial compression under different loading directions is summarized, which provides a theoretical basis for the processing and development of magnesium-based nanoalloys.

Localized crystallization in shear bands of a metallic glass.

Stress-induced viscous flow is the characteristic of atomic movements during plastic deformation of metallic glasses in the absence of substantial temperature increase, which suggests that stress state plays an important role in mechanically induced crystallization in a metallic glass. However, it is poorly understood. Here, we report on the stress-induced localized crystallization in individual shear bands of Zr60Al15Ni25 metallic glass subjected to cold rolling. We find that crystallization in individual shear bands preferentially occurs in the regions neighboring the amorphous matrix, where the materials are subjected to compressive stresses demonstrated by our finite element simulations. Our results provide direct evidence that the mechanically induced crystallization kinetics is closely related with the stress state. The crystallization kinetics under compressive and tensile stresses are interpreted within the frameworks of potential energy landscape and classical nucleation theory, which reduces the role of stress state in mechanically induced crystallization in a metallic glass.