Papers by Author: Alexandre P. Zhilyaev

Paper TitlePage

Authors: Bae Kyun Kim, Jerzy A. Szpunar, Alexandre P. Zhilyaev
Authors: Alexandre P. Zhilyaev, Jenő Gubicza, Santiago Suriñach, Maria Dolores Baró, Terence G. Langdon
Authors: Minoru Furukawa, Z. Horita, Alexandre P. Zhilyaev, Terence G. Langdon
Authors: V.Yu. Gertsman, Alexandre P. Zhilyaev, A.I. Pshenichnyuk
Authors: Keiichiro Oh-ishi, Alexandre P. Zhilyaev, Terry R. McNelley
Abstract: Friction stir processing (FSP) is a severe plastic deformation (SPD) method that has been applied to as-cast NiAl bronze (NAB) materials, which are widely used for marine components. The thermomechanical cycle of FSP results in homogenization and refinement, and the selective conversion of microstructures from a cast to a wrought condition. The physical metallurgy of NAB is complex and interpretation of the effects of FSP on microstructure has required detailed analysis by optical and electron microscopy methods. Annealing and isothermal hot rolling have been employed to confirm microstructure-based estimates of stir-zone peak temperatures. The variation of mechanical properties was assessed by use of miniature tensile samples and correlated with microstructure for samples from stir zones of single and multi-pass FSP. Exceptional improvement in strength – ductility combinations may be achieved by FSP of NAB materials.
Authors: Cheng Xu, Alexandre P. Zhilyaev, Z. Horita, Terence G. Langdon
Abstract: High-pressure torsion (HPT) is an important processing technique in which a disk is subjected to a high pressure with concurrent torsional straining. In principle at least, the imposed strain is zero at the center of the disk and a maximum at the outer edge. This difference suggests, therefore, that materials processed by HPT will exhibit considerable inhomogeneity. This paper describes the results obtained in a series of experiments which were designed to evaluate the evolution of homogeneity during the processing of two materials by HPT. It is demonstrated that it is possible to achieve a reasonable level of homogeneity in both materials but there are important differences which reflect the dependence of the microstructure on the occurrence of dynamic recovery.
Authors: Boris B. Straumal, Gabriel A. López, Eric J. Mittemeijer, W. Gust, Alexandre P. Zhilyaev
Authors: Alexandre P. Zhilyaev, Keiichiro Oh-ishi, Georgy I. Raab, Terry R. McNelley
Abstract: The influence of strain path during equal-channel angular pressing (ECAP) has been evaluated in pure aluminum by orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The material was examined after four pressing operations by route BC in a 90° die, or eight pressing operations by route BC in a 135° die. The von Mises equivalent strains were essentially the same for these two ECAP procedures. The microtexture data indicate that the distortion during ECAP corresponds to a simple shear in a direction approximately parallel to diechannel exit and on a plane perpendicular to the flow plane. For both procedures the OIM data reveal prominent meso-scale band-like features. Lattice orientations in each band correspond to a texture orientation but the particular combinations of orientations depend upon ECAP die angle. High-angle boundaries in the structure correspond to interfaces between the bands.
Authors: Zsolt Kovács, P. Henits, Alexandre P. Zhilyaev, Nguyen Q. Chinh, Ádám Révész
Abstract: Discs of Al85Ce8Ni5Co2 amorphous alloy were severely deformed by high pressure torsion. Severe plastic deformation exceeding equivalent strain of 8.2 induces the formation of nanocrystalline fcc-Al in a more stable residual amorphous matrix. Calorimetric and X-ray diffraction measurements revealed that the deformed outer part of the disc crystallizes into a mixture of equilibrium phases during the first thermal event. However, in the amorphous ribbon the same crystalline mixture develops only after the second stage.
Authors: Alexandre P. Zhilyaev, Terry R. McNelley, Oscar A. Ruano
Abstract: ntense plastic deformation is generally effective in producing grain refinement. IPD methods include equal channel angular pressing/extrusion (ECAP/ECAE), high-pressure torsion (HPT), accumulative roll bonding (ARB), and friction stir processing (FSP), among others. In this work, we summarize the main results on grain refinement by these processing methods and present our own data on microstructure and texture evolution in metals and alloys during ECAP, HPT and FSP. Whereas ECAP and HPT are usually performed with the work piece material initially at room temperature or even at liquid nitrogen temperature to enhance refinement, FSP involves a brief but complex thermomechanical cycle with peak temperatures up to 0.7 0.9 TMelt. Apparently, materials undergo dynamic recrystallization (DRX) during FSP. DRX also occurs also in metals and alloys of low TMelt due to adiabatic heating during HPT performed at room temperature. The paper is devoted to revisiting of previous as well as new results and a comparative analysis of microstructure and texture evolution in commercially pure aluminum and selected pure metals and alloys during ECAP, HPT and FSP in order to illustrate the limits of grain refinement.
Showing 1 to 10 of 14 Paper Titles