China Science

Single pan thermal analyses (SPTA) have been performed on Cu–14.5 wt.% Sn, Cu–21.3 wt.% Sn and Cu–26.8 wt.% Sn peritectic alloys. For this purpose, a SPTA assembly has been built and calibrated. As the latent heat is a function of temperature and composition during solidification of alloys, a new heat flow model coupled to a Cu–Sn thermodynamic database has been defined for the calculation of the corresponding evolutions of the solid mass fraction, fs(T). To verify the accuracy of this model, a close comparison with a microsegregation model that includes back-diffusion in the primary -solid phase has also been conducted successfully. The thermal analyses have finally shown that the Cu–Sn phase diagram recently assessed in the review of Liu et al. is the most reliable.

F. Kohlera?T. Campanella1?S. Nakanishi2?M. Rappaz aEmail:michel.rappaz@epfl.ch

Three glass-forming alloy compositions were chosen for ribbon production and subsequent electron microscopy studies. In situ tensile testing with transmission electron microscopy (TEM), followed by ex situ TEM and ex situ scanning electron microscopy (SEM), allowed the deformation processes in tensile fracture of metallic glasses to be analysed. In situ shear band propagation was found to be jump-like, with the jump sites correlating with the formation of secondary shear bands. The effect of structural relaxation by in situ heating is also discussed. Nanocrystallization near the fracture surface was observed; however, no crystallization was also reported in the same sample and the reasons for this are discussed. Both the TEM and the SEM observations confirmed the presence of a liquid-like layer on or near the fracture surface of the ribbons. The formation of a liquid-like layer was characterized by the vein geometries and vein densities on the fracture surfaces and its dependence on shear displacement, ?, is discussed. A simple model is adapted to relate the temperature rise during shear banding to the glass transition and melting temperatures and this is used to explain the variety of fracture surfaces which are developed for macroscopically identical tensile testing of metallic glasses together with features which exhibit local melting.

D.T.A. Matthewsa?V. Ocelíka?P.M. Bronsvelda?J.Th.M. De Hosson aEmail:j.t.m.de.hosson@rug.nl
[a]Department of Applied Physics, Netherlands Institute for Metals Research; Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands

Constitutive equations are constructed for single-crystal nickel-based superalloys. Account is taken of dislocation glide in the channels of the matrix phase (referred to as ?) of the face-centred cubic (fcc) type, dislocation climb at the interfaces with the reinforcing L12 precipitates (referred to as ??) and the processes leading to cutting of the interfaces by dislocation ribbons via stacking fault shear of the type. A treatment of ribbons produced by the combination of channel dislocations by an appropriate set of dislocation reactions is developed. The model allows the following features of superalloy creep to be recovered: dependence upon microstructure and its scale, effect of lattice misfit, internal stress relaxation, incubation phenomena, the interrelationship of tertiary and primary creep, and vacancy condensation leading to damage accumulation. Using the model, the creep deformation behaviour of the single-crystal superalloy CMSX-4 is studied, with emphasis on the interrelationship between primary and tertiary creep. It is shown that the values for the various parameters used in the modelling are physically reasonable and are related to the microstructure and its evolution during creep. The creep anisotropy prevalent in these materials due to primary creep is recovered correctly.

A. MaaEmail:a.ma@imperial.ac.uk?D. Dyea?R.C. Reedb Email:r.reed@birmingham.ac.uk
[a]Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP, UK;[b]Department of Metallurgy; Materials, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

During fusion welding, the presence of sulfur in steel often affects heat and fluid flow in the weld pool and its geometry. While the role of sulfur during welding of stainless steel plates with the same sulfur content is well understood, welding of stainless steel plates containing different concentrations of sulfur has not yet received proper attention. Here we report an experimental and modeling investigation of gas tungsten arc butt welding of stainless steel plates containing different sulfur concentrations. The main variables studied were sulfur concentrations in the two plates, welding current and welding speed. The results show significant shift of the fusion zone toward the low sulfur steel. The asymmetric fusion zone profile with respect to the original joint interface could be quantitatively explained through numerical modeling of heat transfer and fluid flow considering a bead shift observed experimentally.

S. Mishraa?T.J. Lienertb?M.Q. Johnsonb?T. DebRoyc Email:debroy@psu.edu
[a]Department of Metallurgical Engineering; Materials Science, Indian Institute of Technology Bombay, Mumbai, India;[b]Materials Science; Technology: Metallurgy Group, Los Alamos National Laboratory, Los Alamos, NM, USA;[c]Department of Materials Science; Engineering, The Pennsylvania State University, University Park, PA, USA

Transmission electron microscopy characterizations and elastic properties of two quaternary carbides, i.e. Zr2(Al(Si))4C5 and Zr3(Al(Si))4C6 are reported. The space group and atomic-scale microstructures of both compounds were determined using a combination of selected area electron diffraction, convergent beam electron diffraction, high-resolution transmission electron microscopy and Z-contrast scanning transmission electron microscopy. In addition, the combined experimental and theoretical studies on elastic properties for Zr2(Al(Si))4C5 are presented. A full set of second-order elastic constants, bulk modulus, shear modulus, and Young’s modulus were calculated using first-principles calculations. Both experimental and theoretical works demonstrated that quaternary Zr–Al–Si–C ceramics possess close elastic properties to ZrC. Furthermore, Zr2(Al(Si))4C5 retained a high Young’s modulus up to about 1580 °C, which can be attributed to its comparable activation energy of lattice drag process to that of ZrC.

Z.J. Lina?L.F. Hea?J.Y. Wanga?M.S. Lia?Y.W. Baoa?Y.C. Zhoua Email:yczhou@imr.ac.cn
[a]Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;[b]Graduate School of Chinese Academy of Sciences, Beijing 100049, China

The faceted morphology and dislocation structures in all the facets of austenite precipitates in a duplex stainless steel were investigated with an extended near-coincidence-sites (NCS) method based on the orientation relationship (OR) generated by the O-line model. The prominent facets of the precipitates are parallel to three sets of principal Moiré planes containing high areal density of NCS, respectively. The Burgers vector and the spacing of the misfit dislocations were determined by a Moiré plane trace analysis and a displacement decomposition method. The observed misfit dislocations were consistently explained by the current approach, but the calculated fine dislocations were not observed experimentally. The terrace-ledge-kink structures in terms of both ferrite and austenite lattices were also graphically illustrated. The present geometric approach can also be applied to other systems containing lath- or rod-shaped precipitates, especially when the interfacial structures cannot be described by periodic O-lattice elements.

D. Qiu aEmail:d.qiu@minmet.uq.edu.au?W.-Z. Zhanga
[a]Laboratory of Advanced Materials, Department of Materials Science; Engineering, Tsinghua University, Beijing 100084, China

A publicly available data set has been examined for relationships between average values of porosity,permeability,depth,temperature,pressure,thickness,age,and play type for 11,833 sandstone reservoirs,mostly of Miocene age and younger,from the United States offshore Gulf of Mexico(GOM).Porosity shows wide scatter as a function of burial depth,but the median(P50)porosity trend decreases smoothly with depth.The GOM trend has much higher porosity for the given depth than the P50 trend of sandstone reservoirs worldwide,reflecting rapid sedimentation rates and young ages of GOM reservoirs,most of which have spent relatively little time at temperatures more than 80°C,where quartz cementation becomes active.Multivariate regression analysis shows that porosity is best predicted by temperature(r2=0.40),with the fit improved slightly by adding age and then depth(r2=0.44).Arithmetic average permeability(represented by its logarithm)shows a correlation of maximum and P50 trends with porosity.GOM P50 permeability lies 0.2-0.4 log units below the P50 trend for sandstone reservoirs worldwide,probably reflecting very fine grain size of most GOM sands.Water saturation can be used to calculate the effective(petroleum-filled)porosity of each reservoir,which shows strong correlation with permeability.Grouping the reservoirs by chronozone reveals regular trends of decreasing average porosity and permeability with increasing age,reflecting increasing average depth and temperature with age.Porosity and permeability functions representing depositional sand quality show only subtle differences between different age groupings and play types.The results presented here can be useful for specifying realistic distributions of parameters for both exploration risk evaluation and reservoir modeling.

S.N.Ehrenberg?P.H.Nadeau?and O.Steen

We present a generic algorithm for automating sedimentary basin reconstruction. Automation is achieved through the coupling of a two-dimensional thermotectonostratigraphic forward model to an inverse scheme that updates the model parameters until the input stratigraphy is fitted to a desired accuracy. The forward model solves for lithospheric thinning, flexural isostasy, sediment deposition, and transient heat flow. The inverse model updates the crustal- and mantle-thinning factors and paleowater depth. Both models combined allow for automated forward modeling of the structural and thermal evolution of extensional sedimentary basins. The potential and robustness of this method is demonstrated through a reconstruction case study of the northern Viking Graben in the North Sea. This reconstruction fits present stratigraphy, borehole temperatures, vitrinite reflectance data, and paleowater depth. The predictive power of the model is illustrated through the successful identification of possible targets along the transect, where the principal source rocks are in the oil and gas windows. These locations coincide well with known oil and gas occurrences. The key benefits of the presented algorithm are as follows: [1] only standard input data are required, (2) crustal- and mantle-thinning factors and paleowater depth are automatically computed, and (3] sedimentary basin reconstruction is greatly facilitated and can thus be more easily integrated into basin analysis and exploration risk assessment.

L. H. Rupke?S. M. Schmalholz?D. W. Schmid
Physics of Geological Processes, Oslo University, P.O. Box 1048 Blindern, 0316 Oslo, Norway; Geological Institute, Leonhardstrasse 19, ETH Zurich, 8092 Zurich, Switzerland