Effect of point defects on the amorphization of metallic alloys during ion implantation. [NiTi]

Conference · Tue Jan 01 04:00:00 EST 1985

OSTI ID:6217533

Pedraza, D F; Mansur, L K

A theoretical model of radiation-induced amorphization of ordered intermetallic compounds is developed. The mechanism is proposed to be the buildup of lattice defects to very high concentrations, which destabilizes the crystalline structure. Because simple point defects do not normally reach such levels during irradiation, a new defect complex containing a vacancy and an interstitial is hypothesized. Crucial properties of the complex are that the interstitial sees a local chemical environment similar to that of an atom in the ordered lattice, that the formation of the complex prevents mutual recombination and that the complex is immobile. The evolution of a disorder based on complexes is not accompanied by like point defect aggregation. The latter leads to the development of a sink microstructure in alloys that do not become amorphous. For electron irradiation, the complexes form by diffusional encounters. For ion irradiation, complexes are also formed directly in cascades. The possibility of direct amorphization in cascades is also included. Calculations for the compound NiTi show reasonable agreement with measured amorphization kinetics.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6217533
• Report Number(s): CONF-8510168-4; ON: DE86003088
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360106* -- Metals & Alloys-- Radiation Effects
ALLOYS
AMORPHOUS STATE
BEAMS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTRON BEAMS
INTERMETALLIC COMPOUNDS
ION IMPLANTATION
LEPTON BEAMS
NICKEL ALLOYS
PARTICLE BEAMS
PHYSICAL RADIATION EFFECTS
POINT DEFECTS
RADIATION EFFECTS
TITANIUM ALLOYS