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College Park, Maryland      June 6 - 10 , 2004

T3-C2 (4:15 PM): Implications of Different Strengthening Mechanisms on Intergranular Strains in Various Aluminum Alloys

T. A. Saleh, J. W. Jeon (Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996, USA.), J. Pang, C. R. Hubbard (Metals and Ceramics Division, Oak Ridge National Laboratory), D. W. Brown (Los Alamos Neutron Science Center, Los Alamos National Laboratory), H. Choo (Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996, USA.; Metals and Ceramics Division, Oak Ridge National Laboratory), P. K. Liaw (Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996, USA.), M. A. M. Bourke (Los Alamos Neutron Science Center, Los Alamos National Laboratory)

The presence of intergranular strains in deformed polycrystalline samples due to inhomogeneous deformation is widely recognized. However, the effects of different types of strengthening mechanisms in alloys on the generation of intergranular strains have not been studied systematically. In this experiment, lattice strains were measured for different (hkl) reflections in a series of Al alloys under uniaxial tensile load up to 7 % plastic strain. Precipitation-strengthened Al-2024, Al-7075-T6, Al-6061, and solid-solution strengthened Al-5083 alloys were studied. Both Al-2024 and Al-7075-T6 showed similar lattice strain responses. Reflection (200) shows the largest response with residual strains, upon unloading from 150 MPa, of -1000 με and +850 με parallel and transverse to the tensile axis for Al-2024. The corresponding strain values for Al7075-T6 were -700 με and +720 με respectively. The behavior of the solid-solution strengthened Al-5083 differs from the precipitation-strengthened alloys with the largest residual strain found in reflection (311), not the (200), with a compressive strain of -1000 μεe along the tensile axis. Lattice strains for the other reflections in Al-5083 are within 300 με for both the longitudinal and transverse directions compared to the other alloys. The differences between the Al-5083 sample and the other alloys will be discussed in context of the effect of strengthening mechanism as well as texture.

This work benefited from the use of the Los Alamos Neutron Science Center (LANSCE) at the Los Alamos National Laboratory. This facility is funded by the US Department of Energy under Contract W-7405-ENG-36. This research was also sponsored by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of FreedomCAR and Vehicle Technologies, as part of the High Temperature Materials Laboratory User Program, Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract number DE-AC05-00OR22725.

Additionally, this work is supported by the NSF International Materials Institutes (IMI) Program under Contract DMR-0231320, with Dr. Carmen Huber as the program director.

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