The amorphization of intermetallic compounds by mechanical alloying/milling

Miscellaneous · Tue Jan 01 00:00:00 EST 1991

OSTI ID:5703840

Yoonsung, Cho

Mechanical milling (MM) of Nb{sub 3}Sn, CoZr, and Ni{sub 3}Si compounds induce lattice defects such as chemical disordering and grain boundaries of nanometer dimensions. During MM, Nb{sub 3}Sn, and CoZr formed the amorphous phases while Ni{sub 3}Si formed the nanocrystallites. The amorphization of the intermetallic compounds by MM strongly depends on whether the free energy difference between the crystalline and amorphous phase can be overcome by the free energy increases due to chemical disordering and grain boundaries. The contribution of the free energy increase by chemical disordering is about 35% for the above compounds and thus the major contribution comes from grain boundary of the nanocrystallites. During mechanical alloying (MA) of (Nb + Sn) and (Nb + Sn{sub 2}) at 25 at.% Sn, disordered A15 Nb{sub 3}Sn was formed and then transformed to the amorphous structure. During MA of (Nb + Ge), (Nb + NbGe{sub 2}), etc, the solubility of Ge in the Nb solid solution extended and transformed to a partially amorphous Nb{sub 4}Ge which became completely amorphous due to grain boundary energy provided by further milling. As a conclusion, a new amorphization mechanism by MA/MM was proposed.

• Research Organization: North Carolina State Univ., Raleigh, NC (United States)
• OSTI ID: 5703840
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COBALT ALLOYS
MILLING
NICKEL ALLOYS
NIOBIUM ALLOYS
SILICON ALLOYS
TIN ALLOYS
ZIRCONIUM ALLOYS
AMORPHOUS STATE
CRYSTALLIZATION
GRAIN BOUNDARIES
INTERMETALLIC COMPOUNDS
METALLURGICAL EFFECTS
ALLOYS
CRYSTAL STRUCTURE
MACHINING
MICROSTRUCTURE
PHASE TRANSFORMATIONS
360102* - Metals & Alloys- Structure & Phase Studies
360101 - Metals & Alloys- Preparation & Fabrication