Cost-Effective TiAl based Materials
Because of their inherent low ductility, TiAl-based materials are difficult to fabricate, especially thin gage titanium gamma aluminide (TiAl) sheet and foil. In this paper, an innovative powder metallurgy approach for producing cost-effective thin gage TiAl sheets (with 356 mm long and 235 mm wide, and a thickness of 0.74, 1.09, 1.55, and 2.34 mm, respectively) is presented. The microstructures and tensile properties at room and elevated temperatures of the thin gage TiAl are studied. Results show that these TiAl sheets have a relatively homogenous chemistry, uniform microstructure, and acceptable mechanical properties. This work demonstrates a cost-effective method for producing both flat products (sheet/foil) and complex chunky parts of TiAl for various advanced applications including aerospace and automotive industries.
ELECTRODEPOSITION OF TITANIUM ALUMINIDES FROM ALUMINUM CHLORIDE: 1-BUTYL-3-METHYL IMIDAZOLIUM CHLORIDE IONIC LIQUID by MALLIKHARJUNA REDDY BOGALA RAMANA G. REDDY, COMMITTEE CHAIR
The key for achieving sustainable future depends not only on the discovery of new advanced structural materials, but also on the development of novel energy-efficient technologies for their production and processing in industries. Titanium aluminides are new emerging class of high-temperature structural materials that show promising application in aerospace and automotive industries. Because of their unique properties like low weight, high strength, good oxidative and creep resistance, titanium aluminides are increasingly finding their way to replace steel as structural materials. Compared to the existing industrial techniques, electrodeposition of titanium aluminides in ionic liquid electrolytes is an attractive process because of its low cost, low temperature, good current efficiency, and low energy consumption. In the present study, electrodeposition of titanium aluminides from aluminum chloride-1butyl-3-methylimidazolium chloride (2:1 mole ratio) electrolyte was investigated at 100 °C. Chronopotentiometric experiments were conducted at different current densities (135 to 891 A/m) for 4 h. Dissolution of titanium anode into the melt and electrodeposition of TiAl alloys onto titanium cathode took place at different current densities. Surface morphology and compositional analysis of TiAl alloys were examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) methods. The morphology of TiAl alloy deposits changed from dendritic to granular shape at higher current densities. XRD and EDS analysis have confirmed the presence of disordered face-centered cubic (FCC) lattice in high pure TiAl alloys. The TiAl electrodeposits containing 14.56 to 20.75 atom% Ti were produced with current efficiencies of 60.96 81.35% and energy consumptions of 6.71 12.08 kWh/kg. ii DEDICATION To my parents, sister, brother and friends for their timely support.
Effect of temperature on the solvated electron in 1-propanol
Abstract The technique of pulse radiolysis has been used to study the effect of temperature on the solvated electron in 1-propanol. The spectrum of the solvated electron has been measured in the range 140–298 K. The wavelength at maximum absorption, λ max , decreases with decreasing temperature (corresponding to an increase in the energy, E max ) but the spectral width at half height, ΔE 1 2 , changes little with temperature. At temperatures above ≈180 K, the formation of the solvated electron is complete at the end of the pulse and its spectrum shows no change in shape with time. Below ≈170 K, the absorption spectrum is time-dependent in both liquid and glassy phases, the changes being attributed to the solvation process. The reaction(s) leading to solvated electron formation following the pulse show an activation energy of 22±2 kJ mol − and the solvated electron decays with an activation energy of 20±2 kJ mol −1 . The yield of solvated electrons decreases continuously with decreasing temperature in the range 298-77 K and, at all temperatures studied, is less than the total ionization yield measured by scavenging techniques.