Papers by Keyword: Atom Probe

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Authors: Naoki Maruyama, George D.W. Smith
Abstract: Atomic-scale interface segregation behaviour of Nb and Mo during different stages of recrystallisation of a-Fe has been investigated using a three-dimensional atom probe (3DAP). Experimental procedures to analyse a specific region of interest in the specimens and to determine an orientation relationship between analysed contiguous grains are briefly described, and then analytical artefacts which may affect the measured solute distribution are discussed. Atom probe analysis reveals that Gibbs free energy of segregation of Nb is larger than that of Mo in a-Fe, implying that a stronger solute Nb-interface interaction can be a reason for the larger retardation effect of recrystallisation by Nb addition. The comparison of measured solute profiles at migrating recrystallisation interfaces with calculated solute profiles show that Cahn’s solute drag model gives a reasonable fit to solute profiles for migrating interfaces.
Authors: Paul J. Warren, M. Thuvander, M. Hourai, H. Lane, Alfred Cerezo, George D.W. Smith
Authors: S. Tin, L. Zhang, A.P. Ofori, Michael K. Miller
Abstract: The elemental partitioning characteristics of advanced single crystal Ni-base superalloys containing additions of both Pt and Ru have been investigated using atom probe tomography. Detailed microanalysis revealed Ru additions partitioned preferentially to the disordered matrix, whereas Pt additions tended to partition to the ordered intermetallic γ′ precipitates. The partitioning characteristics of three nominally similar alloys with systematic variations in the levels of Cr, Ru and Pt were investigated. For this particular set of experimental alloys, minor changes in the partitioning characteristics of the constituent elements could be attributed to additions of Cr and Ru. The preferential site occupancy of Pt within the L12 lattice was also statistically quantified with ALCHEMI (atomic site location by channelling enhanced microanalysis). In contrast to the atomic partitioning characteristics of Ru, Pt exhibited a tendency to occupy the Ni sublattice sites in the γ′ structure.
Authors: Christoph Lerchbacher, Silvia Zinner, Harald Leitner
Abstract: The microstructure of the common hot-work tool steel AISI H11 has been characterized by atom probe tomography with the focus on the carbon distribution after the hardening treatment and in the early stages of tempering. The carbon distribution shows significant differences within the probed volumes, regions differently affected by carbon segregation can be observed in some specimens. In all samples pronounced carbon segregation to dislocations and cluster formation is observed. Through all hardened samples no segregation of any substitutional elements has taken place. Heating to 500°C does not significantly change the elemental distribution. Carbon enriched interlath austenite films with peak carbon levels of 6 to 9 at% show a thickness increase with increasing λ. These films and the pre-existing carbon clusters have been found to be nucleation sites for carbide formation during heating to 610°C.
Authors: Yukari Ishikawa, Takeshi Yoshimura
Authors: Peter V. Liddicoat, Tomoyuki Honma, L.T. Stephenson, Simon P. Ringer
Abstract: During age-hardening of certain Al-Zn-Mg-Cu alloys, a 90% hardness increase can occur with 75 seconds. The clustering and precipitation of solute element species during this early rapid hardening (RH) period has been investigated through atom probe tomography, transmission electron microscopy, and Vickers hardness measurements. This study has focussed on the effect of copper by analysing three alloys; Al-2.0Zn-1.8Mg-0.7Cu, Al-2.0Zn-1.7Mg-0.2Cu and Al-1.9Zn-1.7Mg (at.%). The early RH reaction in these alloys accounts for up to 70% of the total hardening (peak hardness minus as-quenched hardness) and takes place during the first 60 seconds of ageing. We report preferred solute-solute interactions in the as-quenched materials. This quenched-in nanostructure acts as a template for subsequent solute clustering, the nature of which we have correlated with ageing.
Authors: Y. Zhang, N. Wanderka, U. Czubayko, F. Zhu, H. Wollenberger
Authors: De Hai Ping, Kazuhiro Hono, Ki Buem Kim
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