Application of Different Extraction Methods for Investigation of Nonmetallic Inclusions and Clusters in Steels and Alloys

The characterization of nonmetallic inclusions is of importance for the production of clean steel in order to improve the mechanical properties. In this respect, a three-dimensional (3D) investigation is considered to be useful for an accurate evaluation of size, number, morphology of inclusions, and elementary distribution in each inclusion particle. In this study, the application of various extraction methods (chemical extraction/etching by acid or halogen-alcohol solutions, electrolysis, sputtering with glow discharge, and so on) for 3D estimation of nonmetallic Al2O3inclusions and clusters in high-alloyed steels was examined and discussed using an Fe-10 mass% Ni alloy and an 18/8 stainless steel deoxidized with Al. Advantages and limitations of different extraction methods for 3D investigations of inclusions and clusters were discussed in comparison to conventional two-dimensional (2D) observations on a polished cross section of metal samples.

Simulation on Agglomeration of Liquid Inclusion Particles in Steel Based on VOF Model

The Micro agglomeration process of liquid inclusion particles in static steel was simulated based on VOF model of fluent software. The results were indicated that: two liquid inclusion particles, which are apart from a certain surface distance, can aggregate into a larger new inclusion particle; in order to promote liquid inclusion particles aggregate and accelerate inclusions flotation to be removed, the following measures can be taken: shortening the inclusion particle surface spacing, reducing the steel viscosity and controlling the composition of liquid inclusion in high interfacial tension area.

An Analytical Model for the Effective Dielectric Constant of a 0-3-0 Composite

An analytical expression for prediction of the effective dielectric constant of a three phase 0-3-0 ferroelectric composite is presented. The analytical results are verified with the experimental results from Nan et al. (2002, “Three-Phase Magnetoelectric Composite of Piezoelectric Ceramics, Rare-Earth Iron Alloys, and Polymer,” Appl. Phys. Lett., 81(20), p. 3831). The analytical model is extended to include the shape of a third phase inclusion to examine the influence of the shape (of the inclusion) on the effective dielectric constant of the composite. The dielectric constant increases as much as seven times when the aspect ratio of the conducting inclusion particle is increased from 1 (sphere) to 10 (spheroid). A comparison of the analytical predictions with the experimental values, which indicate that the increase in aspect ratio of the inclusions has a significant effect on the overall dielectric constant of the composite.

Simulation of Flow Field and Particle Trajectory in EB Cold Hearth Melting Process

Electron beam cold hearth melting process is an efficient method to produce the premium quality titanium alloys, especially to eliminate inclusions. A simulation work was carried out to study the process, concerning the flow field and particle trajectory at three different melt rates. The simulation results show that, when there is an overheat zone near the outlet zone, the molten metal flows to the sidewall of the cold hearth, and from the outlet zone to the inlet zone at the top surface which avoids the inclusion particle flows out the cold hearth. At the bottom of the liquid pool, the fluid flows to the outlet directly along the center plan, which forms a short circuit, decreases the residence time of the inclusion particles; there is a critical density range of inclusion particles, which have more probability to flow out of the cold hearth. The inclusion particles, whose density lower than it, will flow to the sidewall. The inclusion particles, whose density higher than it, will sink into the bottom mushy zone. Both cases let the inclusion have higher probability to eliminate the inclusions.