Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
Displaying 1 - 2 of 2
Filtering by
- Creators: Beura, Vikrant Kumar
- Creators: Korobeinikov, Yuri
Description
The characterization of interface properties in molten slag is crucial for understanding the interface phenomenon and the reactions between slag and metal. This study focuses on examining the influence of Cr2O3, an important surface active oxide, on the wettability and surface tension of slag. Industrial Electric Arc Furnace (EAF) slag with two different Cr2O3 contents (1 wt% and 3 wt%) was investigated using the sessile drop measurement technique at a high temperature of 1650°C. For the preparation of 3 wt% Cr2O3-doped slags, the following crucibles were used: Al2O3, Mo, and MgO. The behavior of crucibles, the dissolution process as well as its effect on the slag thermophysical properties were studied. For the evaluation of surface tension, Mo and MgO substrates were used. The contact angle was measured using the sessile drop method, and the surface tension was calculated using the Young-Laplace-based software. The interaction and wettability behavior between the slag and different substrates was studied. The effects of Cr2O3 content, in correlation with Al2O3, Mo, and MgO, as well as temperature, on the surface tension, and phase formation were analyzed using FactSage 8.2. The results indicate an increase in the formation of solid phases with Al2O3 and Mo dissolution into the slag. The composition of the MoO3 is confirmed with the XRF and EDS analysis. Furthermore, an increase in the formation of the spinel phase was observed with the addition of chromium, which is confirmed via XRD. The increase in the CaCrMo-oxide-based spinel led to a decrease in the surface tension of the slag. The surface tension of the slag pre-melted in a Mo, decreases as the Cr2O3 content increases. The effects of the amounts of Cr2O3 in correlation with Al2O3, MgO, and MoO3 on the slag foaming index were determined using the existing models in the literature.
ContributorsMeena, Neha (Author) / Seetharaman, Sridhar (Thesis advisor) / Alford, Terry (Committee member) / Korobeinikov, Yuri (Committee member) / Arizona State University (Publisher)
Created2023
Description
Solid-state and non-equilibrium processings are of great interest to researchers due to their ability to control and refine bulk and/or surface microstructure of metallic alloys and push them to surpass their conventional properties limit. In this dissertation, solid-state processing i.e., Shear Assisted Processing and Extrusion (ShAPE), and non-equilibrium processes i.e., surface mechanical attrition (SMAT) and additive manufacturing (AM) techniques were used to process the magnesium and aluminum alloys respectively. A synergistic investigation of processing-induced microstructural modification and its effect on corrosion resistance was performed using various ex-situ, quasi in-situ, and in-situ electrochemical, microscopy, and spectroscopy characterization techniques. To evaluate the effect of the same processing condition on a range of microstructures, a variety of magnesium alloys such as AZ31B, Mg-3Si, ZK60, and Pure Mg were processed using a novel solid-state processing method, namely ShAPE. It induced a significant grain refinement, homogenized distribution of second phases, and low residual strain in AZ31B alloy, which contributed toward a noble breakdown potential, stable protective film, and hence better corrosion resistance compared to the parent extruded counterpart. However, with variations in composition, volume fraction, and distribution of second phases with Mg-3Si and ZK60 magnesium alloy an opposite response was inferred indicating a strong dependence of corrosion on underlying microstructure compared to a processing condition. Non-equilibrium processes, i.e. SMAT and AM were utilized to process high-strength 7xxx series aluminum alloys. Continuous high energy impacts of hard balls in room temperature (RT SMAT) and liquid nitrogen (LN2 SMAT) flow environment generated a gradient nanocrystalline surface layer with the dissolution of inherent second phase and precipitation of new phases in aluminum 7075 alloys. RT SMAT showed a reduced anodic dissolution rate and improved film resistance, which was attributed to the thicker and composite oxide layer along with new nanoscale precipitates. Lastly, reactive AM was used to process aluminum 7075 and 7050 alloys which resulted in a refined and textureless microstructure. A reduction in corrosion resistance was observed with precipitation of excessive reactive particles (Ti and B4C) in AM alloys compared to wrought counterparts.
ContributorsBeura, Vikrant Kumar (Author) / Solanki, Kiran N (Thesis advisor) / Peralta, Pedro (Committee member) / Alford, Terry (Committee member) / Ankit, Kumar (Committee member) / Joshi, Vineet V (Committee member) / Arizona State University (Publisher)
Created2022