MICROSCOPIC MECHANISM OF DEFORMATION IN AMORPHOUS METALS.

Format:

Book

Thesis/Dissertation

Author/Creator:

SUZUKI, YOSHIO.

Contributor:

University of Pennsylvania.

Subjects (All):

Materials science.

0794.

Local Subjects:

0794.

Physical Description:

225 pages

Contained In:

Dissertation Abstracts International 46-05B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

A computer simulation of mechanical deformation in an amorphous structure and an X-ray diffraction observation of the creep-induced structural anisotropy were performed in order to investigate the microscopic mechanism of deformation. Earlier computer simulation studies have shown that during deformation the atomic displacements are not spatially uniform, but are localized at several deformation sites. However, the atomic arrangements in those deformation sites have not been clearly identified. In this study bonds between the nearest neighbor atoms were assumed to be the basic units of the structure. The topology of an amorphous structure can be described by the network consisting of these nearest neighbor bonds. The topology of the bond network is conserved by elastic deformation, but it is changed by non-elastic deformation. The local atomic arrangements of the deformation sites were also analysed using the concept of bond network. Shear units in which one bond is exchanged with another bond were found to be important basic units of anelasticity. Small deformation units can be connected with others to form a larger deformation unit, which explains the wide distribution of the activation energies associated with deformation and relaxation. A diffraction study of the anisotropy in the structure factor for an amorphous metal using the energy dispersive X-ray diffraction (EDXD) technique provided valuable information on the atomic scale mechanism of deformation. We found that the distribution of the bond orientations after creep had been shifted toward the direction perpendicular to the tensile axis. This behavior can be explained by the bond rearrangement mechanism of deformation. The study of recovery of the creep-induced structural anisotropy and the effect of preannealing showed that the observed structural anisotropy is due solely to anelastic effect, not due to plastic deformation. In conclusion, we have shown that non-elastic deformation of amorphous metals can be described in terms of the local rearrangements of the atomic bonds, and that the structural anisotropy induced by such bond rearrangements can be experimentally observed by X-ray diffraction.

Notes:

Source: Dissertation Abstracts International, Volume: 46-05, Section: B, page: 1654.

Thesis (Ph.D.)--University of Pennsylvania, 1985.

Local Notes:

School code: 0175.

Access Restriction:

Restricted for use by site license.