Engineering Commons^™

Thermomechanical Process Simulation And Quantification Of Nanoscale Precipitation Influencing Ductility And Strength During Alloy Processing, Alyssa Stubbers

Theses and Dissertations--Chemical and Materials Engineering

Experimental process simulation and quantification of microstructure development during processing are challenging due to limitations with machinery temperature capability, inadequate resolution and sampling volume of currently available characterization techniques, and difficulty characterizing material microstructures as close to processing-relevant conditions as possible. This dissertation addresses how process simulation can be performed using Gleeble thermomechanical technologies and how microstructure development during these processing simulations can be quantified both in-situ and ex-situ.

The first portion of this dissertation demonstrates how Gleeble technologies can be applied to simulate complex material processing conditions in order to produce process-property profiles that can be used to inform …

Characterization Of Residual Stress And Precipitate Evolution In Aluminum 2xxx Self-Reacting Friction Stir Welds, Benjamin Joe Wing

Doctoral Dissertations

2xxx series aluminum alloys possess attractive properties for structural aerospace applications including high strength to weight ratio, corrosion resistance, and stable cryogenic performance. Solid state joining processes are often employed to reduce weld defects and improve weld performance/consistency as many alloys of this range have poor weldability for traditional fusion based joining techniques. One such process, self-reacting friction stir welding (SRFSW) allows for consistent high-quality, welding of large and curved articles is often used in the construction of large structures such as launch vehicle liquid propellant tanks.

Despite the merits of this process, joint softening (a decrease in mechanical properties …

Synthesis Of Sodium Ammonium Hydrophosphate And Sodium Dihydrophosphate Based On Extraction Phosphoric Acid From Central Kyzylkum Phosphorites, Kamola Arifdjanova, Kholtura Mirzakulov, Sherzod Khujamberdiev, Melikulova Gavkhar

CHEMISTRY AND CHEMICAL ENGINEERING

The aim of the research is the synthesis of sodium ammonium hydrogen phosphate and sodium dihydrogen phosphate based on purified extraction phosphoric acid.

The acid was purified from accompanying impurities by precipitation methods using sodium carbonate and metasilicate, washed burnt phosphoconcentrate, barium carbonate, acid neutralization with gaseous ammonia. Pre-neutralization of the purified solution of monoammonium phosphate with sodium carbonate to the ratio Na₂O:P₂O₅ = 0.44 and subsequent drying at a temperature of 50 °С allows to obtain sodium ammonium hydrogen phosphate tetrahydrate, and at 100 °С sodium dihydrogen phosphate monohydrate.

The individuality and purity of …

Integrated Computational Materials Engineering (Icme) Investigation Of Electrical Conductivity And Thermodynamic Stability For Precipitation Strengthened Al-Zn-Zr And Al-Zn-Ni Ternary Alloys, Oladeji Fadayomi

Dissertations, Master's Theses and Master's Reports

High electrical conductivity Al-Zn-TM (TM=Transition metals) alloys with improved mechanical properties and thermal resistance are developed with an integrated computational material engineering (ICME) strategy. From a series of ab initio density functional theory (DFT) simulations assessing combinations of ternary alloys, Al-Zn-Ni and Al-Zn-Zr are determined as alloys with relatively high electrical conductivity compared to several other ternary Al alloy combinations. The zero-temperature stable structure of precipitates formed in these alloys are determined from computed enthalpy of formation as L1₂, with particular focus of examining the influence of Zn on stabilizing the desired L1₂ precipitate phase.

Scanning transmission …

Microstructural Evolution During The Homogenization Heat Treatment Of 6xxx And 7xxx Aluminum Alloys, Pikee Priya

Open Access Dissertations

Homogenization heat treatment of as-cast billets is an important step in the processing of aluminum extrusions. Microstructural evolution during homogenization involves elimination of the eutectic morphology by spheroidisation of the interdendritic phases, minimization of the microsegregation across the grains through diffusion, dissolution of the low-melting phases, which enhances the surface finish of the extrusions, and precipitation of nano-sized dispersoids (for Cr-, Zr-, Mn-, Sc-containing alloys), which inhibit grain boundary motion to prevent recrystallization. Post-homogenization cooling reprecipitates some of the phases, changing the flow stress required for subsequent extrusion. These precipitates, however, are deleterious for the mechanical properties of the alloy …

(Alpha + Gamma) Ultrafine Duplex Structure Formation In Twophase Stainless Steel By High-Pressure Torsion And Annealing, Mie Ota, Kei Ameyama, Daiki Nanya, Sanjay Kumar Vajpai

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Effect Of Rare Earth On The Niobium Carbide Dissolution And Precipitation In Low-Carbon Microalloy Steels, Haiyan Wang, Huiping Ren, Xueyun Gao

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Novel Ternary Magnesium-Tin Alloys By Microalloying, Sadegh Behdad

FIU Electronic Theses and Dissertations

The objective of this research was to explore the possibility of developing novel Magnesium-Tin alloys with improved mechanical properties by micro-alloying. Magnesium is the lightest of all structural metals. It can be machined faster and with almost half the power required for aluminum. There is a limitless supply of magnesium in sea water and it can also be recycled at 5% of initial energy requirements. These properties make magnesium an ideal green alternative to replace metals and polymers in automotive, aerospace, biomedical and defense sectors. The potential weight reduction in the US automotive market alone, leads to 100 billion gallons …

Formation Of Caco3 Particle And Conductivity Of Na2co3 And Cacl2 Solution Under Magnetic Field On Dynamic Fluid System, Nelson Saksono, Setijo Bismo, Roekmijati Widaningroem, Azwar Manaf

Makara Journal of Technology

Hard water causes the CaCO3 scale formation on the pipe walls and heat exchanger equipments in industrial or domestic water processes. A great number of experimental researches on the prevention of the CaCO3 precipitation process by magnetic field have been carried out. In this research, Na2CO3 and CaCl2 solutions was magnetized in the circulated flow condition (dynamic fluid system). The velocity of fluid and the circulation time was modified to examine its influences to the magnetization process. CaCO3 content was measured by titration method of EDTA complexometry. Conductivity test was conducted to find out hydrate ion bonding. The results showed …

Crystal Habit Of Caco3 Under Different Carbonation Methods, J Ariyaprayoon, U Leela-Adisorn, A Supsakulchai

Journal of Metals, Materials and Minerals

The saturated solutions of Ca(OH)2 were carbonated by CO2 in air under static and turbulent conditions. The saturation state of starting solution and carbonation methods had effect on the crystal habit. The phase of CaCO3 precipitated from saturated solution is calcite. No metastable phase of CaCO3 was found.

Analysis Of Nonequilibrium Hcp Precipitate Growth In Fcc Matrices: Application To Al–Ag, Daniel Finkenstadt, Duane D. Johnson

Duane D. Johnson

Hexagonal-close-packed (hcp) γ-precipitates with large aspect ratios form rapidly in some face-centered cubic (fcc) solid-solutions. No model explains the observed time-dependent increase in aspect ratio, nor irregular intermediate growth shapes. We propose a nonequilibrium process involving trapezoidal offshoots (controlled only by energetics) that governs the growth behavior (kinetics) and yields nonequilibrium structures in agreement with observation. Then, combining nucleation theory and diffusion-limited growth both of secondary nuclei and ledges, we derive a general growth equation for γ-precipitates due to solute-segregation to precipitate–matrix interfaces that includes our modification of the Jones–Trivedi model for thickening to account for the slow growth of …

Nano-Size Hydroxyapatite Powders Preparation By Wet-Chemical Precipitation Route, N Monmaturapoj

Journal of Metals, Materials and Minerals

In this study, wet-chemical process was performed to prepare nano-size hydroxyapatite (HA) powders (≈10 nm) by varying concentration (low, medium and high) of the starting solutions in order to increase the amount of as-dried HA powders with different process conditions. Particle sizes and density were analyzed and differential thermal analysis was used to determine the glass transition (Tg) and the onset crystallization (Tc) temperatures. XRD and SEM were performed to identify phases and microstructure. The wet-chemical precipitation using low concentration of starting solution under reflux environment could be the optimize process to induce the formation of hydroxyapatite rather than tricalcium …

Microstructure And Mechanical Properties Of En Aw 6082 Aluminium Alloy Prepared By Equal-Channel Angular Pressing, M Fujda, T Kvačkaj

Journal of Metals, Materials and Minerals

The mechanical properties and microstructure of EN AW 6082 aluminium alloy subjected to severe plastic deformation (SPD) and natural ageing are compared with those of extruded and artificially aged state (initial state) and quenched state of alloy after solution annealing. Quenched state of alloy was deformed at room temperature by equal channel angular pressing (ECAP) following route C up to three passes. Polyedric microstructure of quenched state was considerably changed by SPD. Deformation bands with different amount of deformation were observed in microstructure of ECAPed state, which indicated non-uniform deformation across the cross-section of ECAPed specimen. Ultimate tensile strength (UTS) …

Leaching, Purification And Precipitation Of Glen Scheelite Concentrates, Harold L. Coolidge

Bachelors Theses and Reports, 1928 - 1970

The leaching, purification and precipitation of the Glen scheelite concentrates were performed to acquaint the student with the equipment and processes involved. The concentrates were obtained through the courtesy of the Minerals Engineering Company. Leaching was carried out in the high-pressure autoclave; whereas the purification and precipitation were carried out in laboratory beakers.