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.
Shape and surface texture of molten droplets deposited on cold surfaces
When a molten droplet impacts on a cold surface, the interaction between solidification and fluid dynamics can lead to different shapes and surface textures of deposited droplets. This article presents an experimental study on deposition of small droplets (39 μm diameter) of molten wax ink on solid surfaces. Our results show that both the final shape and the surface texture of deposited droplets are extremely sensitive to deposition conditions, which include initial temperature of droplets, type of substrate surface and distance between substrate and printhead. Different surface textures are observed and shown to depend on the thermal and flow histories of ink droplets during the process of impact. A test using crystalline wax reveals crystallization as one of the major factors in determining the final texture.