Microstructural dependence of effective stresses and activation volumes during creep

Journal Article · Mon Oct 01 04:00:00 EDT 1984 · Acta Metall.; (United States)

DOI:https://doi.org/10.1016/0001-6160(84)90220-7· OSTI ID:6065376

Morris, M A; Martin, J L

Macroscopic measurements of internal stresses and activation volumes made by stress relaxation or reduction tests performed in the past have led to controversial interpretations about the strain rate controlling mechanism during secondary creep. The fact that these macroscopic measurements provide only average values over the crystal makes it very difficult to relate them to microscopic activated events in which dislocations overcome obstacles locally. In this work, the microscopic values of local effective stresses existing during secondary creep of an Al-Zn alloy have been measured for different conditions of stress and temperature. At the same time, the variation of the substructure parameters such as the subgrain size and subboundary mesh size has been studied. Detailed analysis of dislocation emission at subboundaries has been made and it appears that junction recombination generally occurs by glide and cross-slip. A simple equation has been developed relating all the different parameters, and the microscopic activation volumes have been deduced. The latter appear to decrease with increasing stress. The activation volumes are related to the mesh size, confirming that a mechanism of junction recombination at subboundaries under the action of local effective stresses produces dislocation emission and controls the creep rate.

• Research Organization: Institut de Genie Atomique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne
• OSTI ID: 6065376
• Journal Information: Acta Metall.; (United States), Journal Name: Acta Metall.; (United States) Vol. 32:10; ISSN AMETA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOY SYSTEMS
ALLOYS
ALUMINIUM ALLOYS
BINARY ALLOY SYSTEMS
BOUNDARY CONDITIONS
CREEP
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
DESTRUCTIVE TESTING
DISLOCATIONS
LINE DEFECTS
MATERIALS TESTING
MECHANICAL PROPERTIES
MICROSTRUCTURE
RECOMBINATION
RELAXATION
SLIP
STRESS RELAXATION
STRESSES
TESTING
ZINC ALLOYS