Numerical simulation of the flow, solidification, and solute transport in a billet mold under electromagnetic stirring

In this study, a coupled three-dimensional model of the billet continuous casting mold process was developed to investigate the characteristics of the macroscopic transmission behaviors under different mold electromagnetic stirring (M-EMS) parameters. The mold curvature was also considered during the modeling of electromagnetic and flow fields. The results indicate that the macroscopic physical quantities had nonsymmetrical distributions in the mold because of the mold curvature. However, the influence of mold curvature on the electromagnetic force could be ignored. The horizontal swirling flow caused by the M-EMS became stronger as the current density increased, which enhanced the dissipation of the molten steel superheat and promoted the growth of the solidification shell. However, the flushing of the bias hot jet slowed the growth of the local solidified shell. Meanwhile, the washing effect of the melt flow on the solidification front caused the solute element content near the billet surface to fluctuate. In addition, the distribution of the solute element content became more uneven in the strand transverse direction as the current density increased.

Distribution of Al Element of Ti–6Al–4V Joints by Fiber Laser Welding

In the process of laser welding, the uneven distribution of solute elements caused by element burning loss and flow of molten pool affects the quality of joints. In this paper, butt welding experiments were conducted on the 3 mm thick Ti–6Al–4V specimens with different preset ratios of Al and Si powders by using 4 kW fiber laser. The distribution of Al solute element and its influence on the microstructure and mechanical properties of the final weld joint were investigated. The results showed that the self-diffusion of Al element and the flow of molten pool affects the alloy elements distribution in laser welding. And the microhardness of the welded joint with Ti–6Al–4V and 90% Al + 10% Si powders was significantly higher than that with only Ti–6Al–4V, with the difference of about 130HV. At the same time, in the joint with 90% Al and 10% Si powders, the acicular α’ size was finer, and basketweave microstructure was present as well. This research is helpful to better understand the distribution of Al solute element and its influence on the joint quality during laser welding of Ti–6Al–4V alloy, which provides a certain reference for improving the weld or surface properties of Ti–6Al–4V alloy during laser processing.

Growth Rate and Surface Morphology of 4H-SiC Single Crystal Grown under Various Supersaturations Using Si-C Solution

We have investigated growth rate and surface morphology of 4H-SiC single crystal grown from Si-C solution with various supersaturation levels at growth temperature in the range from 1840 to 2140 °C. The growth rate depends linearly on the amount of supersaturated carbon, irrespective of the growth temperature. This indicates that the growth is limited by the transfer of solute element onto the crystallization front. The adequate condition for stable solution growth are discussed with respect to high growth rate and surface morphology.

The Influence of Heat Treatment Parameters on the Thermal Diffusivity of WE54 and Elektron 21 Magnesium Alloys

In the present study, the thermal diffusivity and conductivity of WE54 and Elektron 21 alloys were studied. The results showed the thermal diffusivity of WE54 and Elektron 21 alloys were temperature and microstructure dependent. The thermal diffusivity of both alloys was dependent on the content of the solute element in the α-Mg matrix. The solid solution of Y and Gd in Mg has a lower thermal conductivity than alloys where the intermetallic Mg3(Nd,Gd) and Mg14Y2Nd phases are present. The formation of strengthening phases during ageing caused the consumption of the solute element in the α -Mg matrix, and improved the thermal conductivity of the alloys.

Distribution of alloying elements and the corresponding structural evolution of Mn–Sb alloys in high magnetic field gradients

The distribution of alloying elements and the corresponding structural evolution of Mn–Sb alloys in magnetic field gradients were investigated in detail. It was found that a high magnetic field gradient could control the distribution of solute element in the alloys during the solidification process and therefore resulted in the coexistence of both primary MnSb and Sb phases or the aggregation of the primary MnSb with a continuous change in morphology. The positions where these primary phases located depended on the direction of field gradient. The control of the solute element distribution by a high magnetic field gradient was realized through the magnetic buoyancy force that could drive the migration of Mn element in the melt, originating from the difference in the magnetic susceptibility between Mn and Sb. The effectiveness of this control depends on the alloy composition, specimen dimension, cooling rate, and |BdB/dz| value.