Showing papers in "Acta Materialia in 1998"

TL;DR: In this paper, a microbend test method for determining the plasticity length scale has been developed and described, which involves the bending of a thin annealed foil around a small diameter cylindrical mandril, followed by measurement of the unloaded and loaded radii of curvature.

TL;DR: In this article, experiments were conducted on high purity aluminum to investigate the process of grain refinement during equal-channel angular (ECA) pressing, where samples were subjected to 1 to 4 pressings and then sectioned for microstructural examination in three mutually perpendicular directions.

TL;DR: In this article, the fine-scale precipitation that occurs during age hardening of Al alloy 6061 has been studied using differential scanning calorimetry (DSC), APFIM and transmission electron microscopy (TEM).

TL;DR: In this article, the effects of size on predominantly mechanical properties of materials are reviewed at a first-order level, and important aspects can be understood from the point of view of the interaction of a characteristic length (which may be as diverse as the dislocation radius of curvature at a given stress or the magnetic exchange length) with a size parameter (grain or particle size, or film thickness).

TL;DR: In this article, a general methodology is proposed for the determination of surface residual stresses and residual plastic strains using instrumented sharp indentation, which is assumed to be equibiaxial and uniform over a depth (beneath the indented surface) which is at least several times larger than the indentation contact diameter, and the indenter load and geometry can be so chosen as to minimize or maximize the contact radius to seek the broadest range of applicability and validity of the proposed method by recourse to macro-, micro- and nanoindentation of elastoplastic

TL;DR: In this paper, the crystal structure of β″, one of the strengthening phases in the commercially important Al-Mg-Si alloys, is determined by using of high resolution electron microscopy (HREM) and electron diffraction (ED).

TL;DR: In this article, a new model is presented to describe the hardening behavior of cell-forming crystalline ma- terials at large strains, based on a cellular dislocation structure consisting of two phases: the cell walls and the cell interior.

TL;DR: In this paper, an analytical model is developed for model foams with simple cubic unit cells consisting of heated slender cylinders, based on existing heat transfer data on convective crossflow through cylinder banks.

TL;DR: In this article, a model for precipitation kinetics integrating nucleation growth and coarsening is presented, which allows the description of competitive kinetics of heterogeneous and homogeneous precipitation.

TL;DR: A bonelike apatite layer can be formed even on metals such as silicon, titanium and its alloys, tantalum, and organic polymers such as poly(ethylene terephthalate), polyether sulfone and polyethylene in a simulated body fluid with ion concentrations nearly equal to those of human blood plasma, when their surfaces are a little modified.

TL;DR: In this paper, the flow and relaxation of the Zr46.75Ti8.25Cu7.5Ni10Be27.5 bulk metallic glass forming alloy was investigated in the supercooled liquid state and the glass transition region using parallel plate rheometry, three-point beam bending as well as differential scanning calorimetry.

TL;DR: In this article, the deformation microstructure is subdivided by dislocation boundaries having different characteristics depending on the orientation of the deformed grain, and the majority of the dislocations in the boundaries originate from active slip systems predicted by a Schmid factor analysis.

TL;DR: The effect of hydrogen on the interaction between dislocations and other elastic centers in high-purity aluminum and stainless steel has been directly observed during deformation experiments in situ in an environmental cell transmission electron microscope as discussed by the authors.

TL;DR: In this paper, the anisotropy of plasticity in b.c. metals is decomposed into two parts: a sensitivity of the Peierls stress to non-glide elements of the applied stress, and small edge fractional dislocation components in the screw dislocation core.

TL;DR: In this article, the development of elastic lattice strains during uniaxial loading for selected families of grains with specific orientations was modeled using a self consistent scheme, and the results were evaluated by neutron diffraction.

TL;DR: In this paper, a model for the yield stress of ultra-fine grained materials based upon Coble creep was proposed, where a grain size distribution was incorporated into the analysis to account for a distribution of grain sizes occurring in most specimens.

TL;DR: In this article, the effect of the distribution of solid between the cell faces and edges on mechanical properties using finite element analysis of idealized 2D (hexagonal honeycomb) and 3D (closed-cell tetrakaidecahedral foam) cellular materials was investigated.

TL;DR: In this paper, a metallic glass with the nominal composition Zr41.25Ti13.75Cu12.5-Ni10Be22.5 was used as the matrix in continuous fiber composites reinforced with tungsten and 1080 steel wire.

TL;DR: In this article, a study has been made of the spontaneous growth of tin whiskers from tin electrodeposits on a phosphor bronze sheet, and the driving force for the evolution of tin worms is a biaxial compressive stress of about 8 MPa developed in tin deposits by the formation of an intermetallic compound of Cu 6 Sn 5, especially in grain boundaries of tin films.

TL;DR: In this paper, the influence of the channel angle Φ, defined as the angle of intersection of the two channels within the die, on the subsequent microstructure attained by pressing was investigated.

TL;DR: In this article, the particle size and the dislocation structure in inert gas condensed nanocrystalline copper were determined by high-resolution X-ray diffraction profile analysis, and the root-mean-squared strains were explained by the presence of dislocations.

TL;DR: In this article, the high-strain-rate mechanical response of α-titanium is examined in terms of the underlying deformation mechanisms that govern its macroscopic behavior.

TL;DR: In this article, a superdislocation model was proposed to predict the yield point during indentation of tungsten and an iron alloy using the change in shear stress between the elastically and fully plastic loading conditions.

TL;DR: In this paper, the deformation behavior of Ni 3 Al during dynamic recrystallization DRX was investigated and a new model for the flow curve was proposed that accounts for the percolation character of necklace structures.

TL;DR: In this article, the ageing kinetics of a ternary Al-Zn-Mg alloy were investigated, and the coupling between prestraining and subsequent ageing was investigated in terms of competition between homogeneous precipitation and heterogeneous precipitation on dislocations.

TL;DR: In this paper, the deformation mechanism of polycrystalline martensitic NiTi shape memory alloys under tension and compression was investigated and it was shown that under compression, the material is quickly strain hardened and no flat stress-plateau is observed.

TL;DR: In this paper, aluminum foams made by two liquid-state production methods are investigated and the cellular structure and mechanical properties of these foams are investigated, and the influence of the production method on the structural performance of the materials is discussed.

TL;DR: In this article, a full pattern fitting of diffraction spectra is applied to a comprehensive investigation of a material modification process, if appropriate physical models are used to describe the scattering event instead of semi-empirical functions.

TL;DR: In this article, a pure aluminium polycrystal having an average grain size of 300μm has been strained in tension at room temperature and the flow stress has been determined at four different strains (0.05,0.14, 0.22 and 0.34).

TL;DR: In this article, the effect of small amounts of oxygen (0.28-0.6 ǫ at) on phase formation and the thermal stability of bulk samples of the Zr 65 Al 7.5 Cu 17.c.