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Blobaum, K.J.M.; Krenn, C.R.; Wall, M.A.; Massalski, T.B.; Schwartz, A.J. |
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Nucleation and growth of the [alpha]' martensitic phase in Pu-Ga alloys |
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Journal Article |
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2006 |
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Abstract |
Acta Materialia |
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Corporate Author |
Acta Mater. |
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54 |
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15 |
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Summary Language |
4001-4011 |
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Phase transformations; Martensitic phase transformation; Nucleation of phase transformations |
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Abbreviated Series Title |
In a Pu-2.0 at.% Ga alloy, it is observed experimentally that the amount of the martensitic α' product formed upon cooling the metastable δ phase below the martensite burst temperature (Mb) is a function of the holding temperature and holding time of a prior conditioning (“annealing”) treatment. Before subjecting a sample to a cooling and heating cycle to form and revert the α' phase, it was first homogenized for 8 h at 375 [degree sign]C to remove any microstructural memory of prior transformations. Subsequently, conditioning was carried out in a differential scanning calorimeter apparatus at temperatures in the range between -50 and 370 [degree sign]C for periods of up to 70 h to determine the holding time and temperature that produced the largest volume fraction of α' upon subsequent cooling. Using transformation peak areas (i.e., the heats of transformation) as a measure of the amount of α' formed, the largest amount of α' was obtained following holding at 25 [degree sign]C for at least 6 h. Additional time at 25 [degree sign]C, up to 70 h, did not increase the amount of subsequent α' formation. At 25 [degree sign]C, the Pu-2.0 at.% Ga alloy is below the eutectoid transformation temperature in the phase diagram and the expected equilibrium phases are α and Pu3Ga, although a complete eutectoid decomposition of δ to these phases is expected to be extremely slow. It is proposed here that the influence of the conditioning treatment can be attributed to the activation of α-phase embryos in the matrix as a beginning step toward the eutectoid decomposition, and we discuss the effects of spontaneous self-irradiation accompanying the Pu radioactive decay on the activation process. Subsequently, upon cooling, certain embryos appear to be active as sites for the burst growth of martensitic α' particles, and their amount, distribution, and potency appear to contribute to the total amount of martensitic product formed. A modeling approach based on classic nucleation theory is presented to describe the formation of α-phase embryos during conditioning. The reasons why the holding times during conditioning become eventually ineffective in promoting more α' formation on cooling are discussed in terms of the differences in the potency of the embryos created in the δ matrix during conditioning and in terms of growth-impeding volume strains in the matrix resulting from an increasing number of martensite particles, thus opposing further growth. It is suggested that the disparate amounts of the α' formation reported in the literature following various studies may be in part a consequence of the fact that conditioning times at ambient temperatures are inevitably involved in any handling of radioactive samples prior to testing. |
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NU @ karnesky @ |
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1916 |
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Bakó, Botond; Clouet, Emmanuel; Dupuy, Laurent M.; Blétry, Marc |
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Dislocation dynamics simulations with climb: kinetics of dislocation loop coarsening controlled by bulk diffusion |
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Journal Article |
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2011 |
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Philosophical Magazine |
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Philosophical Magazine |
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91 |
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23 |
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3173-3191 |
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* dislocation climb, * dislocation loops, * coarsening, * diffusion, * dislocation dynamics |
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Dislocation climb mobilities, assuming vacancy bulk diffusion, are derived and implemented in dislocation dynamics simulations to study the coarsening of vacancy prismatic loops in fcc metals. When loops cannot glide, comparison of the simulations with a coarsening model based on the line tension approximation shows good agreement. Dislocation dynamics simulations with both glide and climb are then performed. Allowing for glide of the loops along their prismatic cylinders leads to faster coarsening kinetics, as direct coalescence of the loops is now possible. |
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Taylor & Francis |
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1478-6435 |
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doi: 10.1080/14786435.2011.573815 |
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NU @ karnesky @ |
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11160 |
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Wang, Hua; Zhu, Naqiong; Shi, Wen; Li, Lin; Liu, Rendong |
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Effect of Mn and P on precipitation behavior and solute distribution in ultra-low carbon bake hardening steels |
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Journal Article |
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2011 |
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Journal of Materials Science |
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46 |
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9 |
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2982-2990 |
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Engineering |
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The effect of Mn and P on types of precipitates as well as solute distributions in ultra-low carbon bake hardening (ULC-BH) steels was originally investigated in this paper. Three samples of hot-rolled ULC-BH steels (Ti–V, Ti–V–Mn, and Ti–V–P) were prepared. The types of precipitates in the three samples were characterized with scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and further calculated by Thermo-Calc. The different types of nanometer sized vanadium carbides are clearly characterized by SEM and TEM, and results of calculation and experiments are generally in agreement. Besides, the solute distributions in Ti–V–Mn and Ti–V–P steels were detected by three-dimensional atom probe (3DAP). It is found that no Ti, N, or S elements are present in both of the two steels, and the distribution patterns of the solute elements in the two steels are completely determined. Results show that SEM, TEM combining with 3DAP can well detect the existence of elements added into the bake hardening steels, and are very useful techniques for the base of the further investigation of mechanical properties and bake hardening phenomenon in bake hardening steels. |
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Springer Netherlands |
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0022-2461 |
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NU @ karnesky @ |
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11049 |
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M. Young, J.D. DeFouw, J. Frenzel, D.C. Dunand |
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Cast Replicated NiTiCu Foams with Shape-Memory Properties |
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Journal Article |
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2012 |
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Metallurgical and Materials Transactions A |
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43 |
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8 |
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2939-44 |
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NU @ michaeljsrawlings @ |
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11446 |
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Liu, J.; Zhirnov, V. V.; Wojak, G. J.; Meyers, A. F.; Choi, W. B.; Hren, J. J.; Wolter, S. D.; McClure, M. T.; Stoner, B. R.; Glass, J. |
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Electron emission from diamond coated silicon field emitters |
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Journal Article |
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1994 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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65 |
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2842-2844 |
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Field Emission |
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3128 |
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Rendulic, K. D.; Müller, E. W. |
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Twinning of iridium in a field ion microscope |
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Journal Article |
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1966 |
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Journal of Applied Physics |
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J. Appl. Phys. |
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37 |
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2593-2595 |
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twinning iridium; Field Ion Microscopy |
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5858 |
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Furuno, Kazuko; Akamatsu, Hiroki; Oh-ishi, Keiichiro; Furukawa, Minoru; Horita, Zenji; Langdon, Terence G. |
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Microstructural development in equal-channel angular pressing using a 60° die |
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Journal Article |
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2004 |
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Acta Materialia |
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Acta Mater. |
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52 |
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9 |
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2497-2507 |
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Aluminum; Equal-channel angular pressing; Grain boundary misorientations; Texture; Ultrafine-grained microstructures |
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Billets of pure aluminum and an Al–1%Mg–0.2%Sc alloy were successfully processed using equal-channel angular pressing (ECAP) with a die having an internal channel angle of 60°. Careful inspection of the microstructures after ECAP revealed excellent agreement, at both the macroscopic and the microscopic levels, with the theoretical predictions for shearing using a 60° die. The grain sizes introduced with the 60° die were slightly smaller than with a conventional 90° die; thus, the values with these two dies were ~1.1 and ~1.2 small mu, Greekm in pure Al and ~0.30 and ~0.36 small mu, Greekm in the Al–Mg–Sc alloy, respectively. Tensile testing of the pure aluminum at room temperature revealed similar strengthening after processing using either a 60° or a 90° die. In tests conducted at 673 K, the Al–Mg–Sc alloy processed with the 60° die exhibited significantly higher elongations to failure due primarily to the larger strain imposed with this die. It is shown using orientation imaging microscopy that superplastic flow in the Al–Mg–Sc alloy produces an essentially random texture and a distribution of boundary misorientations that approximates to the theoretical distribution for an array of randomly oriented grains. |
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NU @ karnesky @ |
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530 |
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Gómez de Salazar, J. M. ; Barrena, M. I. |
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Role of Al2O3 particulate reinforcements on precipitation in 7005 Al-matrix composites |
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Journal Article |
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2001 |
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Scripta Materialia |
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Scripta Mater. |
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44 |
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10 |
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2489-2495 |
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Aluminum; Composites; Microstructure; Intermetallics phases; TEM |
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NU @ karnesky @ |
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533 |
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Goodman, S. R.; Brenner, S. S.; Low, J. R. |
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An FIM-atom probe study of the precipitation of copper from iron-1 4 at pct copper II Atom probe analyses |
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Journal Article |
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1973 |
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Metallurgical Transactions |
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4 |
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10 |
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2371-2378 |
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metallurgical applications; atom probe field ion microscopy |
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6593 |
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Kim, K. B.; Zhang, Y.; Warren, P. J.; Cantor, B. |
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Crystallization behaviour in a new multicomponent Ti16.6Zr16.6Hf16.6Ni20Cu20Al10 metallic glass developed by the equiatomic substitution technique |
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Journal Article |
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2003 |
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Philosophical Magazine A |
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Phil. Mag. A |
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83 |
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2371-2381 |
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9237 |
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