Materials Science and Engineering Commons^™

Thermomechanical Mechanisms That Cause Adhesion Of Aluminum High Pressure Die Castings To The Die, Alex Monroe

Dissertations, Master's Theses and Master's Reports

In high pressure die casting (HPDC) of aluminum, cast material adhering to die is a significant defect. Adhesion occurs in two primary ways. The casting may stick preventing its removal from the die. Aluminum can also adhere to the die and buildup in local areas on the die surface with additional casting cycles. This second form of adhesion is called soldering. Lubricant is the best technology to control all forms of adhesion, but it comes at the cost of casting porosity, blisters, reduced die life, and increased die casting machine wear. New strategies to prevent adhesion are desired to eliminate …

The Effects Of Molybdenum, Chromium, And Niobium On Gray Iron For Brake Rotor Applications, Matthew Hasbrouck

Dissertations, Master's Theses and Master's Reports

Brake rotor composition and microstructure must be optimized for thermal and mechanical performance to avoid thermal-mechanical cracking, excessive wear, and to reduce noise. Niobium is an element that increases the strength and wear resistance of gray iron; however, the interaction of niobium with other common alloying elements (chromium and molybdenum) is not well understood. Thirteen gray cast iron alloys were produced with varying levels of carbon equivalent (CE), Cr, Mo, and Nb. Bars with four different diameters (8, 14, 22, and 30 mm) were cast from each alloy and microstructural and physical properties such as graphite flake morphology, pearlite spacing, …

Atomistic Monte Carlo Simulation Study Of Phase Transitions In Metal Alloys, Xiaoxu Guo

Dissertations, Master's Theses and Master's Reports

The atomic-scale Monte Carlo simulation study focuses on the intrinsic behaviors of a defect-free crystal that undergoes a cubic-to-tetragonal martensitic transformation. The quasi-spin variable associated with the lattice sites characterizes the local unit cells of the orientation variants of the ground-state martensite phase, which interact with each other through long-range elastic interactions. It is shown that the diffuse scattering in the premartensitic austenite state results from the spatial correlation of the atomic-scale heterogeneous lattice displacements and manifests the displacement short-range ordering. The effects of temperature, elastic anisotropy, and shear modulus softening on the diffuse scattering and displacement short-range ordering are …

Analyzing Variation In Dispersoid Formation In Aluminum Alloys By Minor Changes In Homogenization Temperature, Brendan Treanore

Dissertations, Master's Theses and Master's Reports

The homogenization of billets in the aluminum extrusion industry is a critical step that removes chemical segregation from casting, dissolves low melting point phases, forms nanoscale dispersoid phases, and promotes the beta to alpha transformation of iron particles in the matrix. With ever increasing use of aluminum extrusion in the automotive industry there is a constant need for increased efficiency and consistency in processing of extruded aluminum. The work in this thesis explores the effects of 10°C differences in the homogenization temperature on the formation of dispersoids in 6082 alloys used in the automotive industry. The role of dispersoids is …

New Horizons For Processing And Utilizing Red Mud, M. Archambo

Dissertations, Master's Theses and Master's Reports

Red mud is an industrial slurry waste that is produced as a byproduct of the Bayer process for alumina. The waste is generated in large quantities, up to a ratio of 2:1 against the valued product alumina. Red mud exhibits many chemical and physical properties that categorize it as a hazardous material. Due to the addition of sodium hydroxide in processing, the pH is typically at values close to 13. Small particle size discourages separation from water for disposal, so drying red mud happens over many years.

The pH of red mud can be reduced with inexpensive reagents. Carbon dioxide …

Role Of Eta Phase Evolution On Creep Properties Of Nickel Base Superalloys Used In Advanced Electric Power Generation Plants, Ninad Mohale

Dissertations, Master's Theses and Master's Reports

Advanced fossil energy power generation plants require materials that withstand high temperatures and corrosive environments. One such material that is used in steam turbines is Nimonic 263. It is a nickel-base superalloy that is principally strengthened by gamma primephase (Ni₃(Ti, Al)) and has an L1₂structure. At extended times and at turbine operating temperatures however, eta (Ni₃Ti) phase is known to form at the expense of gamma prime. Eta has a complex DO₂₄structure and is the stable phase between 750°C and 900°C, but with slow kinetics of formation. Little is understood about eta …

Anaerobic Reductive Bioleaching Of Manganese Ores, Neha Sharma

Dissertations, Master's Theses and Master's Reports

The increasing demand of manganese in the industries and various hindrances in its production from low grade ores by conventional method has made it imperative for researchers around the world to develop a method of manganese extraction from low grade ores that is both environment friendly and economical. Bioleaching has shown significant potential in manganese extraction and efficiencies of extraction have been found to be 70-98% with the help of various bacteria and fungi.

This study focuses on extraction of manganese with the help of mixed bacterial strains that have been collected from their natural anaerobic environment. The extraction of …

Exploring Rapid Solidification And Equal Channel Angular Pressing In The Fabrication Of Mg-Based Alloys For Medical Applications, Emily Tom

Dissertations, Master's Theses and Master's Reports

The development of magnesium bioresorbable implants has become increasingly popular due to the increased need for temporary implants and magnesium’s excellent biocompatibility and suitable elastic modulus. Even though magnesium is an excellent candidate, when alloyed with other metals magnesium’s corrosion rate becomes too rapid for bioresorbable medical applications. The investigation into novel processing techniques to control the formation of precipitates to improve mechanical strength and ductility as well as corrosion rates has become of interest. This work investigates the combination of two nonequilibrium processing techniques, rapid solidification (RS) and equal channel angular pressing (ECAP), and the effects it has on …