Intergranular fracture along migrated boundaries in ordered Ni/sub 4/Mo

Journal Article · Sat Oct 01 00:00:00 EDT 1988 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/S0036-9748(88)80266-7· OSTI ID:6001778

Brooks, C R; Sanganeria, M

The alloy Ni-20 at. % Mo is FCC and disordered (..cap alpha.. phase) above 868/sup 0/C, and below this temperature it forms a superlattice of the D1a type (..beta.. phase). Rapid cooling from the ..cap alpha.. region prevents the formation of ..beta... Reheating in the range 700-800/sup 0/C results in the relatively rapid formation of the ordered phase. The ordering reaction occurs by preferential arrangement of Ni and Mo atoms on the FCC lattice, so that the ..beta.. has a close packed structure and a crystallographic relation to the former ..cap alpha... Six crystallographic variants of ..beta.. form and three types of domain boundaries. Thus inside the ..cap alpha.. grains a fine domain structure forms with crystallographic continuity between the domains. It is only at the former ..cap alpha.. boundaries that high angle boundaries exist between ..beta.. crystals. Aging results in a coarsening of the domains and accompanying this coarsening is an increase in strength and a drastic reduction in ductility. For example, in the ..cap alpha.. form, the alloy has a ductility of about 60%, whereas aging at 775/sup 0/C for 3 min. reduces the ductility to about 5%. Fracture occurs along the former ..cap alpha.., high angle boundaries.

• Research Organization: Materials Science and Engineering Dept., The Univ. of Tennessee, Knoxville, TN (US)
• OSTI ID: 6001778
• Journal Information: Scr. Metall.; (United States), Vol. 22:10
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MOLYBDENUM ALLOYS
GRAIN BOUNDARIES
NICKEL ALLOYS
DUCTILITY
INTERGRANULAR CORROSION
MECHANICAL PROPERTIES
MICROSTRUCTURE
SUPERLATTICES
ALLOYS
CHEMICAL REACTIONS
CORROSION
CRYSTAL STRUCTURE
TENSILE PROPERTIES
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties