Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Publication
Articles 1 - 3 of 3
Full-Text Articles in Physics
Energy Pathways And Directionality In Deformation Twinning, S. Kibey, J. B. Liu, Duane D. Johnson, H. Sehitoglu
Energy Pathways And Directionality In Deformation Twinning, S. Kibey, J. B. Liu, Duane D. Johnson, H. Sehitoglu
Duane D. Johnson
We present ab initiodensity functional theory calculations of twinning energy pathways for two opposite twinning modes, (111)[112¯] and (111)[1¯1¯2], in fcc materials to examine the directional nature of twinning which cannot be explained by classical twin nucleationmodels or the “twinnability” criterion. By accounting for these energy pathways in a multiscale model, we quantitatively predict the critical twinning stress for the (111)[1¯1¯2] mode to be substantially higher compared to the favorable (111)[112¯] mode (whose predicted stresses are in agreement with experiment), thus, ruling out twinning in the (111)[1¯1¯2] mode.
Generalized Planar Fault Energies And Twinning In Cu–Al Alloys, S. Kibey, J. B. Liu, Duane D. Johnson, H. Sehitoglu
Generalized Planar Fault Energies And Twinning In Cu–Al Alloys, S. Kibey, J. B. Liu, Duane D. Johnson, H. Sehitoglu
Duane D. Johnson
We report ab initio density functional theory calculations of generalized planar fault energies of fcc Cu–xAl (x=0, 5.0, and 8.3at.%) alloys. We investigate the effects of substitutional solute Al on the unstable intrinsic γus and twin γutstacking faultenergies (SFEs). Our results reveal an increased tendency of Cu–Al to deform preferentially by twinning with increasing Al content, consistent with experiment. We attribute this mechanical behavior to appreciable lowering of the twinning barrier γut, along with the stable intrinsic and twin SFEs.
Segregation Of Bismuth To Triple Junctions In Copper, K.-M. Yin, Alexander H. King, T.E. Hsieh, F.-R. Chen, J.J. Kai, L. Chang
Segregation Of Bismuth To Triple Junctions In Copper, K.-M. Yin, Alexander H. King, T.E. Hsieh, F.-R. Chen, J.J. Kai, L. Chang
Alexander H. King
Bismuth segregation in copper has been studied using energy-dispersive X-ray spectrometry (EDX) in a JEOL 2010F transmission electron microscope. In addition to the expected solute enrichment at grain boundaries, we have observed extremely high concentrations of bismuth at certain triple junctions, with significantly greater enrichment factors than in the adjacent grain boundaries. It is shown here that the triple junction segregation is a function of the parameters of the grain boundaries at the triple line, and existence of this type of segregation implies that the affected triple junctions embody excess free energy. At least one of the observed triple junctions …