The nature of directional strain softening

Journal Article · Sat Oct 01 00:00:00 EDT 1983 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/0036-9748(83)90279-X· OSTI ID:6468911

Lowe, T C; Miller, A K

Softening transients are sometimes seen in metals following a change in direction of straining. One example of such softening is that occuring upon a strain direction reversal, for example, during uniaxial reversed cyclic deformation at a large strain amplitude. In such a case, the magnitude of the flow stress decreases slightly for a brief period after having passed through a maximum immediately following each strain direction reversal. This behavior is commonly observed in aluminum during deformation over a wide range of temperatures. Similar softening behavior is seen following strain direction changes in multiaxial deformation of aluminum, copper, and steel. All of these softening behaviors are called ''directional strain softening'' since they are observed following changes in straining direction. The physical processes that occur during directional strain softening involve heterogeneous dislocation substructures. Hasegawa, et al. have identified the dissolution of heterogeneous substructures such as cell and subgrain boundaries as the predominant microstructural change that occurs during directional strain softening in high purity aluminum. At room temperature, cell walls formed by 4.5% prestrain in tension partially dissolve and reform during subsequent straining in compression. Similarly, at higher temperatures, subgrain boundaries formed during tensile prestraining completely dissolve and reform during compressive straining. The mechanism by which this softening occurs has been studied in aluminum and copper. Detailed dislocation interactions have been proposed that depend upon cross slip; this explains the greater tendency for directional strain softening in high stacking fault energy metals.

• Research Organization: Department of Materials Science and Engineering, Stanford University, Stanford, CA
• OSTI ID: 6468911
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Vol. 17:10; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALUMINIUM
COPPER
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELEMENTS
GRAIN BOUNDARIES
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
STACKING FAULTS
STRAIN SOFTENING
STRESS ANALYSIS
TEMPERATURE EFFECTS
TEMPERATURE GRADIENTS
TENSILE PROPERTIES
TRANSITION ELEMENTS