Browsing by Subject "aluminum"

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Laser-Induced Spall Of Aluminum And Aluminum Alloys At High Strain Rates
(2007-12) Dalton, D. A.; Brewer, J.; Bernstein, A. C.; Grigsby, W.; Milathianaki, D.; Jackson, E.; Adams, R.; Rambo, P.; Schwarz, J.; Edens, A.; Geissel, M.; Smith, I.; Taleff, E.; Ditmire, T.; Dalton, D. A.; Brewer, J.; Bernstein, A. C.; Grigsby, W.; Milathianaki, D.; Jackson, E.; Taleff, E.; Ditmire, T.
We conducted laser-induced spall experiments aimed at studying how a material's microstructure affects the tensile fracture characteristics at high strain rates (> 10(6) s(-1)). We used the Z-Beamlet Laser at Sandia National Laboratory to drive shocks and to measure the spall strength of aluminum targets with various microstructures. The targets were recrystallized, high-purity aluminum (Al-HP RX), recrystallized aluminum + 3 wt.% magnesium (Al-3Mg RX), and cold-worked aluminum + 3 wt.% magnesium (Al-3Mg CW). The Al-3Mg RX and Al-3Mg CW are used to explore the roles that solid-solution alloying and cold-work strengthening play in the spall process. Using a line-VISAR (Velocity Interferometer System for Any Reflector) and analysis of recovered samples, we were able to measure spall strength and determine failure morphology in these targets. We find that the spall strength is highest for Al-HP RX. Analysis reveals that material grain size plays a vital role in the fracture morphology and spall strength results.
Letter to UT Board of Regents from J.C. Melcher on 1938-07-06
(1938-07-06) Melcher, J.C.
The O-Na And Mg-Al Anticorrelations In Turn-Off And Early Subgiants In Globular Clusters
(2001-04) Gratton, R. G.; Bonifacio, P.; Bragaglia, A.; Carretta, E.; Castellani, V.; Centurion, M.; Chieffi, A.; Claudi, R.; Clementini, G.; D'Antona, F.; Desidera, S.; Francois, P.; Grundahl, F.; Lucatello, S.; Molaro, P.; Pasquini, L.; Sneden, Christopher; Spite, F.; Straniero, O.; Sneden, Christopher
High dispersion spectra (R greater than or similar to 40 000) for a quite large number of stars at the main sequence turn-off and at the base of the giant branch in NGC 6397 and NGC 6752 were obtained with the UVES on Kueyen (VLT UT2). The [Fe/H] values we found are -2.03 +/- 0.02 +/- 0.04 and -1.42 +/- 0.02 +/- 0.04 for NGC 6397 and NGC 6752 respectively, where the first error bars refer to internal and the second ones to systematic errors (within the abundance scale defined by our analysis of 25 subdwarfs with good Hipparcos parallaxes). In both clusters the [Fe/H]'s obtained for TO-stars agree perfectly (within a few percent) with that obtained for stars at the base of the RGB. The [O/Fe] = 0.21 +/- 0.05 value Re obtain for NGC 6397 is quite low, but it agrees with previous results obtained for giants in this cluster. Moreover, the star-to-star scatter in both O and Fe is very small, indicating that this small mass cluster is chemically very homogenous. On the other hand, our results show clearly and for the first time that the O-Na anticorrelation (up to now seen only for stars on the red giant branches of globular clusters) is present among unevolved stars in the globular cluster NGC 6752, a more massive cluster than NGC 6397. A similar anticorrelation is present also for Mg and Al, and C and N. It is very difficult to explain the observed Na-OI and Mg-Al anticorrelation in NGC 6752 stars by a deep mixing scenario; we think it requires some non internal mechanism.
Simulated Effect of Laser Beam Quality on the Robustness of Laser-Based AM System
(University of Texas at Austin, 2019) Flood, Aaron; Liou, Frank
In many metal AM techniques, a laser is used as the heat source and in some applications, it can be advantageous to work off of the focal plane. When operating outside of focus, the beam quality of the laser can have drastic impacts on the ability to manufacture quality parts. This study investigates the effect of the beam quality and distance from the focal plan on the ability to deposit Ti-64, aluminum, and steel through the simulation of the blown powder process.
Spall And Dynamic Yielding Of Aluminum And Aluminum Alloys At Strain Rates Of 3X10(6) S(-1)
(2009-12) Dalton, D. A.; Worthington, D. L.; Sherek, P. A.; Pedrazas, N. A.; Bernstein, A. C.; Quevedo, H. J.; Rambo, P.; Schwarz, J.; Edens, A.; Geissel, M.; Smith, I. C.; Taleff, E. M.; Ditmire, T.; Dalton, D. A.; Worthington, D. L.; Sherek, P. A.; Pedrazas, N. A.; Bernstein, A. C.; Quevedo, H. J.; Taleff, E. M.; Ditmire, T.
We have explored the role that grain size, impurity particles and alloying in aluminum play in dynamic yielding and spall fracture at tensile strain rates of similar to 3x10(6) We achieved these strain rates shocking the aluminum specimens via laser ablation using the Z-Beamlet Laser at Sandia National Laboratories. The high purity aluminum and 1100 series aluminum alloy produced very different spall strengths and nearly the same yield strengths. In contrast, various grain-sized Al + 3 wt. % Mg specimens presented the lowest spall strength, but the greatest dynamic yield strength. Fracture morphology results and particle analysis are presented along with hydrodynamic simulations to put these results in context. Impurity particles appeared to play a vital role in spall fracture at these fast strain rates. Alloying elements such as Mg seem to be the dominant factor in the dynamic yield results.
Spreading and Packing of Alumina Powder Using a Displacement-controlled Roller in SLFS
(University of Texas at Austin, 2023) Bayazitoglu, Kaya J.; Cassoli, Matthew; Beaman, Joseph J.; Kovar, Desiderio
Selective laser flash sintering (SLFS) is a powder bed fusion process that enables direct additive manufacturing of ceramics. Similar to other powder bed fusion processes, the density of the ceramic powder bed impacts attainable density of the final part. Experiments were conducted using a spray-dried alumina powder that was spread and then packed using a displacementlimited roller. The spreadability of the powder was visually assessed. The microstructure of the resulting compacted powder was compared to a traditional method of pressing ceramic powder into a pellet using a die and hydraulic press. Packed regions were sintered to final density and compared in a scanning electron microscope to samples hydraulically pressed at known pressure to evaluate the efficacy of a roller-based packing process.
Study of Different Aging Conditions for Analysis of Microstructure and Mechanical Properties of F357 Alloy Fabricated in LPBF Printer
(2022) Medrano, V.A.; Caballero, K.; Arrieta, E.; Benedict, M.; Wicker, R. B.; Medina, F.
Aluminum F357 is a widely used material for casting in aerospace and additive manufacturing industry. Heat treatments are commonly applied to some aluminum alloys to modify its properties. With a further study on the aging and performance of the F357 with 3D printing technology, several industries benefit of this, military, automotive and aerospace are some examples, because the numerous components casted in service. This work presents mechanical properties of F357 specimens fabricated with EOS technology and subjected to heat treatments. Heat treatments conditions were applied to tensile specimens and tested. Furthermore, the specimens were subjected to artificial thermal aging for 100 h and 1000 h at two different temperatures (285 ºF and 350 ºF), and their mechanical properties were also determined. Finally, remarks on the comparison between the heat treatments and the effect of thermal aging on the microstructures and mechanical properties of the specimens will be presented.
Synthesis and Structures of Boron Dihalides Supported by the C6F5-Substituted Beta-Diketiminate Ligand Hc(Cme)(2)(Nc6F5)(2) (-)
(2008-03) Vidovic, Dragoslav; Reeske, Gregor; Findlater, Michael; Cowley, Alan H.; Vidovic, Dragoslav; Reeske, Gregor; Findlater, Michael; Cowley, Alan H.
The new boron dihalides of the type [HC(CMe)(2)(NC6F5)(2)]BX2 (X = Cl, Br, I) have been prepared and characterized by single-crystal X-ray diffraction. Of the various synthetic approaches explored, the best method in terms of yield and product purity involves the silylhalide elimination reaction of the silylated iminoamine [HC(CMe)(2)(NC6F5)(N{SiMe3}C6F5)] with BX3. Chloroborenium salt [HC(CMe)(2)(NC6F5)(2)BCl][AlCl4] was prepared by treatment of [HC(CMe)(2)(NC6F5)(2)]BCl2 with AlCl3 in CH2Cl2 solution. This salt was also structurally authenticated and represents the first such data for a beta-diketiminate-supported haloborenium cation.
Texas Business Review, August 1957
(Bureau of Business Research, The University of Texas at Austin, 1957-08) Stockton, John R.; McCormick, Clifford E., Jr.; Drenner, Robert H.; Chute, A. Hamilton; Taniguchi, Izumi; Dale, Alfred G.
Texas Business Review, November 1983
(Bureau of Business Research, The University of Texas at Austin, 1983-11) The University of Texas at Austin
Wire+Arc Additive Manufacturing of Aluminum
(University of Texas at Austin, 2014) Gu, Jianglong; Cong, Baoqiang; Ding, Jialuo; Williams, Stewart W.; Zhai, Yuchun
Wire+Arc Additive Manufacturing is very suitable for the production of large scale aluminium parts. However implementation is currently limited by issues such as porosity and low mechanical properties. We have studied the utilization of new deposition processes such as pulsed advanced cold metal transfer which allows modification of the thermal profile resulting in refined equiaxed microstructure and elimination of porosity. Standard and new feedstock compositions are being evaluated and developed with ultimate tensile strengths of up to 260 MPa with 17% elongation being obtained in the as-deposited condition. Post build heat treatments compositional changes and high-pressure inter-pass rolling are being investigated in order to increase the strength further.