Showing papers in "Acta Materialia in 1999"

TL;DR: In this paper, the accumulative roll-bonding (ARB) method was proposed to introduce high plastic strain without any geometrical change if the reduction in thickness is maintained to 50% every rolling pass.

TL;DR: In this article, Nye's dislocation tensor is defined as a measure of geometrically necessary dislocations (GNDs), based on the integrated properties of dislocation lines within a volume.

TL;DR: In this paper, a three-dimensional atom probe (3DAP) and transmission electron microscopy (TEM) was used to characterize the solute clusters and the metastable precipitates in aged Al-Mg-Si alloys.

TL;DR: In this paper, the tensile behavior of a polycrystal austenitic stainless steel at 0.2Tm is discussed in terms of back and effective stresses with the help of qualitative and quantitative TEM observations.

TL;DR: In this article, the mechanical behavior of a commercially pure titanium (CP-Ti) is systematically investigated in quasi-static (Instron, servohydraulic) and dynamic (UCSD's recovery Hopkinson) compression.

TL;DR: In this paper, the tensile and compressive stress-strain behaviors were established on aged single crystals ([100, [110], and [111] orientations) and polycrystalline NiTi materials.

TL;DR: In this paper, the Zr57Nb5Al10Cu15.4Ni12.6 bulk metallic glass forming liquid is reinforced with WC, SiC, W, or Ta particles.

TL;DR: In this article, the role of annealing twinning in low stacking-fault energy (SFE) materials as a means to achieve this aim has been satisfactorily explained.

TL;DR: In this paper, a 3DAP and a high-resolution electron microscope (HREM) was used to study the clustering and partitioning behavior in the early crystallization stage of an Fe{sub 73.5}Si{sub 13.5]B{sub 9}Nb{sub 3}Cu{sub 1} amorphous alloy.

TL;DR: Grain boundaries can be effectively controlled to produce or enhance their beneficial effects and also to diminish or reduce their detrimental effects on bulk properties in polycrystalline materials as mentioned in this paper, which remains a serious problem of material processing and development.

TL;DR: In this article, a comprehensive stochastic model for simulating the evolution of dendritic crystals during the solidification of binary alloys was developed, which includes time-dependent calculations for temperature distribution, solute redistribution in the liquid and solid phases, curvature, and growth anisotropy without further assumptions on the nucleation and growth of Dendrite crystals.

TL;DR: In this paper, a Burgers orientation relationship between the α and the β phases has been assumed to allow for easy slip transmission across the α/β interfaces, and a simple model is presented based on the accumulation of residual dislocations at both the α /β interface and the α matrix, which provides insight into the mechanism of slip transmission, strain hardening and primary creep of these colony structures.

TL;DR: In this paper, a structural model of the η-Zn-Mg phase was constructed on the basis of the structural characteristics in the observed images and the structure of the MgZn 2 phase.

TL;DR: In this article, the phase conversion occurs after the alumina TGO has cracked on thermal cycling and the underlying bond-coat alloy is depleted of aluminum with concurrent enrichment of the oxide by Cr, Co and Ni.

TL;DR: In this paper, the plastic behavior of two model f.c. metals, Ni and Cu, with different stacking fault energies, and average grain sizes in the range of 3-12nm, is analyzed.

TL;DR: In this paper, the superplastic behavior of a fine-grained AZ91 alloy, processed by equal channel angular extrusion, has been investigated in a low temperature range of 423 −523 K. The experimental results showed a stress exponent of 2 and the activation energy for super-plastic flow was in agreement with that for grain boundary diffusion of magnesium.

TL;DR: In this paper, the creep performance of (001)-orientated superalloy single crystals at temperatures beyond 1000 C was analyzed and it was demonstrated that methods of interpretation which, assume a proportionality between the creep strain rate and creep strain, are unable to account for creep hardening which occurs as a consequence of rafting.

TL;DR: In this paper, a general theory for axisymmetric indentation of piezoelectric solids within the context of fully coupled, transversely isotropic elasticity models is presented.

TL;DR: In this article, the authors modified the Burke equation to take into account a linear dependence of grain-boundary pinning on grain size, and the form of the resulting grain growth curve is surprisingly similar to Burke's solution; in fact, a constant rescaling of the boundary mobility parameter is sufficient to map one solution approximately onto the other.

TL;DR: In this article, the initiation and development of damage inside a 6061 Al alloy reinforced with SiC particles has been studied during in situ mechanical tests using high resolution synchrotron X-ray tomography.

TL;DR: In this paper, the Gibbs energy dissipation approach is applied to the solute drag approach to phase transformations and applied to a wedge-shaped description of the properties of the interface, a very flexible treatment is obtained but it is difficult to decide how to choose the model parameters.

TL;DR: The tensile and compressive stress-strain behavior of closed cell aluminium alloy foams (trade name "Alulight") has been measured and interpreted in terms of its microstructure as discussed by the authors.

TL;DR: In this article, computer simulations of a dislocation slip process through circular or linear obstacles, that are extensions of earlier work by Forman et al., were conducted. But the dependence of the strengthening stress on the obstacle size was found to be less than that predicted by equations currently in use, particularly for linear obstacles.

TL;DR: In this paper, a local Mn-depleted zone (MDZ) has been observed to develop in the vicinity of the steel-Ti2O3 interface, which is believed to be a dominant driving force for the heterogeneous nucleation of intragranular ferrite.

TL;DR: In this paper, the kinetics of γ′ rafting in single crystals at 950°C have been studied using scanning and transmission electron microscopies, and it is concluded that the threshold strain is a quantity suitable for distinguishing between rafting occurring in the “elastic� and “plastic” regimes.

TL;DR: In this paper, the authors studied constrained grain-boundary diffusion in polycrystalline thin metal films on substrates, where no sliding and no diffusion are allowed at the film/substrate interface.

TL;DR: In this paper, a geometrically nonlinear theory of martensitic transformations is used to study the cubic to monoclinic transition in the technologically important Ti-Ni shape memory alloys.

TL;DR: In this paper, the effects of several types of geometric imperfections, such as plateau borders, cell edge misalignments, fractured cell edges, missing cells, inclusions and cell size variations, on the thermal and structural fire retardance of cellular metallic foams are identified.

TL;DR: In this article, it is shown that the adhesion at interfaces between dissimilar materials is strongly affected by both segregation and the extent of plasticity in the adjoining material, particularly when one of these is a metal (or thermoplastic).

TL;DR: In this article, the tension-tension and compression-compression cyclic properties are measured for an open cell Duocel foam of composition Al 6101-T6, and a closed cell “Alporas” foam with composition Al 5Ca-3Ti (wt%).