Papers by Author: Enrique J. Lavernia

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Authors: A.P. Newbery, Byung Ahn, P. Pao, S.R. Nutt, Enrique J. Lavernia
Abstract: Mechanical milling of Al alloy powder in liquid nitrogen leads to a large reduction in the scale of the microstructure and results in material with high thermal stability and strength. However, it is important to consolidate the powder and achieve bulk material with sufficient toughness and ductility for structural applications. In this investigation, hot isostatic pressing, followed by quasiisostatic forging and hot rolling, were performed to fabricate Al 5083 plate with a predominantly ultra-fine grained microstructure. Plate produced in this way possessed enhanced tensile strength and ductility, exceeding that of conventionally processed material.
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Authors: F.H. Froes, C. Suryanarayana, W. Quist, Enrique J. Lavernia, B.I. Bondarev, N.F. Anoshkin, I.S. Polkin, O.K. Fatkullin, V. Samarov, A.B. Notkin
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Authors: E. Chew, H.H. Kim, C. Ferraris, Yong Hao Zhao, Enrique J. Lavernia, C.C. Wong
Abstract: The addition of calcium (Ca) simultaneously improves the ductility and strength of UFG Au wires. Based on the observation on stacking faults, microstructures, simulation results and significant effect of Ca on grain boundary related properties, it is inferred that segregation of Ca to stacking faults and grain boundaries has occurred to induce effective stacking fault energy (SFE) reduction and properties improvement. Considering the known greater impact of SFE in UFG/ NC metals, segregating dopants are proposed to be an effective strategy for achieving dual improvement in this class of materials. Also, dopant selection criteria for this purpose is also suggested and verified.
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Authors: D. Cheng, G. Trapaga, J.W. McKelliget, Enrique J. Lavernia
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Authors: Kyung H. Chung, Jong Sang Lee, Rodolfo-Martín Rodriguez, Dong Hyuk Shin, Enrique J. Lavernia
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Authors: Sheng Long Dai, J.P. Delplanque, Enrique J. Lavernia
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Authors: Byung Ahn, R. Mitra, A.M. Hodge, Enrique J. Lavernia, S.R. Nutt
Abstract: Al 5083 alloy powder was mechanically milled in liquid nitrogen to achieve a nanocrystalline (NC) structure having an average grain size of 50 nm with high thermal stability, and then consolidated by quasi-isostatic (QI) forging. The consolidation resulted in ultrafine grains (UFG) of about 250 nm, and the bulk material exhibited enhanced strength compared to conventionally processed Al 5083. The hardness of as-cryomilled powder and the UFG material was measured by nanoindentation using loading rates in the range of 50−50,000 /N/s, and results were compared with the conventional grain size alloy. Negative strain rate sensitivity was observed in the cryomilled NC powder and the forged UFG plate, while the conventional alloy was relatively strain rate insensitive.
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Authors: Osman Ertörer, Troy D. Topping, Ying Li, Yong Hao Zhao, Wes Moss, Enrique J. Lavernia
Abstract: The room temperature tensile behavior of commercially pure titanium (CP-Ti), cryomilled under different conditions and forged quasi-isostatically into bulk form, was studied in detail. The results demonstrate that the ductility of cryomilled titanium can be improved, and that the mechanical properties can be tailored using three specific strategies: the use of liquid argon as cryomilling media, introduction of coarse grained regions, and low temperature heat treatment. Cryomilling in a liquid argon environment, which differs from the widely used nitrogen cryogenic environment, was found to have a particularly strong influence on ductility, as it prevents nitrogen embrittlement. The contribution of coarse grains and heat treatment to ductility are also introduced and discussed using a comparative approach.
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