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Roy S.,Indian Institute of Science | Suwas S.,Indian Institute of Science | Tamirisakandala S.,FMW Composite Systems Inc. | Tamirisakandala S.,Air Force Research Lab | And 2 more authors.
Acta Materialia | Year: 2011

Hypoeutectic boron addition (0.1 wt.%) to Ti-6Al-4V is known to cause significant refinement of the cast microstructure. In the present investigation, it has been observed that trace boron addition to Ti-6Al-4V alloy also ensures excellent microstructural homogeneity throughout the ingot. A subdued thermal gradient, related to the basic grain refinement mechanism by constitutional undercooling, persists during solidification for the boron-containing alloy and maintains equivalent β grain growth kinetics at different locations in the ingot. The Ti-6Al-4V alloy shows relatively strong texture with preferred components (e.g. ingot axis||[0 0 0 1] or [1 0 1̄0]) over the entire ingot and gradual transition of texture components along the radius. For Ti-6Al-4V-0.1B alloy, significant weakening characterizes both the high-temperature β and room-temperature α texture. In addition to solidification factors that are responsible for weak β texture development, microstructural differences due to boron addition, e.g. the absence of grain boundary α phase and presence of TiB particles, strongly affects the mechanism of β → α phase transformation and consequently weakens the α phase texture. Based on the understanding developed for the boron-modified alloy, a novel mechanism has been proposed for the microstructure and texture formation during solidification and phase transformation. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

McReynolds K.S.,UES, Inc. | Tamirisakandala S.,FMW Composite Systems Inc.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2011

Isothermal oxidation experiments in air were performed on Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) with a bimodal microstructure in the temperature range 811 K to 922 K (538 °C to 649 °C) for up to 500 hours, and α-case depths were quantified using metallography. Alpha-case depth followed a parabolic variation with time. Alpha-case depths in excess of 10 μm formed above 811 K (538 °C) and 100-hour exposures. An activation energy of 244 kJ/mol was estimated for diffusion of oxygen in the α phase of Ti-6242. © 2011 The Minerals, Metals & Materials Society and ASM International.

McEldowney D.J.,University of Dayton | Tamirisakandala S.,FMW Composite Systems Inc. | Miracle D.B.,Air Force Research Lab
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2010

The Ti-6Al-4V (Ti-64) alloys modified with two levels of boron (1B and 1.7B (wt pct)) representing hypoeutectic and hypereutectic compositions, produced via a prealloyed powder metallurgy approach, were subjected to various standard heat treatments of Ti-64 to study the microstructural evolution and its influence on tensile properties. Boron-modified Ti-64 (Ti-64B) alloys exhibited differences in microstructural response to heat treatment compared to that of Ti-64 due to variations in constituent phase fractions and the influence of TiB on the beta-to-alpha phase transformation kinetics. The tensile elastic modulus of Ti-64B alloys increased nearly linearly with the boron content (or TiB volume fraction) and the increase could be satisfactorily predicted with an isostrain rule of mixtures (ROMs) and the Halpin-Tsai model. The Ti-64-1B possessed a good combination of tensile strength (1200 to1370 MPa) and ductility (10 to 13 pct), while Ti-64-1.7B exhibited high strength (1300 to 1695 MPa) and modest ductility (2 to 3.5 pct). Coarse primary TiB particles present in Ti-64-1.7B were found to initiate premature failure. Strength modeling revealed that load sharing by the micron-sized TiB whiskers provides the major contribution for the increase in yield strength. © 2010 The Minerals, Metals & Materials Society and ASM International.

Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase I | Award Amount: 99.98K | Year: 2009

FMW Composite Systems, Inc., in collaboration with Aerojet (OEM), proposes to develop nano-enhanced titanium alloy components for advanced light weight Divert and attitude control systems (DACS), which are capable of replacing current materials to achieve improved performance, net weight reductions, improve producibility, improve reliability, and lower cost. A plan of approach will be developed using design, experimental, modeling and simulation tools. The proof-of-concept will be demonstrated by fabricating an article out of a selected nano-enhanced titanium alloy using an affordable process leader. Test coupons will be produced and characterized for relevant properties to demonstrate the performance. Preliminary manufacturability analysis and design trade studies will be performed to assess the benefits over the baseline.

Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase II | Award Amount: 729.99K | Year: 2009

Superior high-temperature performance requirements for highly stressed rotating components of the compressor section in advanced Army turboshaft engines cannot be met by the existing materials and require sophisticated materials solution concepts. The objective of this SBIR program is to develop a reinforced high temperature titanium material system for impeller applications in advanced Army turboshaft engines to increase the performance, reduce the specific fuel consumption, and enhance the affordability. FMW, in collaboration with Honeywell Aerospace (aero engine original equipment manufacturer), proposed a nano-enhancement concept in Phase I and demonstrated the proof-of-concept via design trade studies, subscale article fabrication, and preliminary mechanical property evaluations. Nano-enhancement approach identified exceptional potential to meet the performance challenges in advanced turboshaft engine impellers. In Phase II, FMW-Honeywell team proposes to fully develop, optimize, scale-up, and mature the nano-enhanced titanium alloy impeller technology. A prototype impeller article, representative of the turboshaft engine, will be fabricated and machined into a fully-featured article for spin-pit testing. Manufacturability, machinability, and affordability aspects will be evaluated and risk reduction strategies will be developed. Detailed material characterization that includes microstructural quantifications, grain flow analysis, failure mechanisms, and microstructural variability analysis, will be conducted. Extensive testing on coupons extracted from various locations and orientations of the prototype article will be performed to generate material data under static and dynamic loading conditions at room and elevated temperatures relevant for the impeller. Impeller spin test data will be analyzed and compared with the baseline results to quantify the benefits. Phase II research and development effort will mature the nano-enhanced titanium impeller technology readiness to the level necessary for engine test demonstration.

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