Role of interfacial dislocations on creep of a fully lamellar tial

Conference · Mon Aug 16 04:00:00 EDT 1999

OSTI ID:12553

Hsiung, L M ^[1]; Nieh, T G

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1. LLNL

Deformation mechanisms of a fully lamellar TiAl ({gamma} lamellae: 100 {approximately} 300 nm thick, {alpha}{sub 2} lamellae: 10 {approximately} 50 nm thick) crept at 760 C have been investigated. It was found that, as a result of a fine structure, the motion and multiplication of dislocations within both {gamma} and {alpha}{sub 2} lamellae are limited at low creep stresses (< 400 MPa). Thus, the glide and climb of lattice dislocations have insignificant contribution to creep deformation. In contrast, the motion of interfacial dislocations on {gamma}{alpha}{sub 2} and {gamma}{gamma} interfaces (i.e. interface sliding) dominates the deformation at low stresses. The major obstacles impeding the motion of interfacial dislocations was found to be lattice dislocations impinging on lamellar interfaces. The number of impinging lattice dislocations increases as the applied stress increases and, subsequently, causes the pileup of interfacial dislocations on the interfaces. The pileup further leads to the formation of deformation twins. Deformation twinning activated by the pileup of interfacial dislocations is suggested to be the dominant deformation mechanism at high stresses (> 400 MPa).

• Research Organization: Lawrence Livermore National Lab., CA (US)
• Sponsoring Organization: USDOE Office of Defense Programs (DP) (US)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 12553
• Report Number(s): UCRL-JC-135382; KC0201050; KC0201050
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CREEP
DEFORMATION
DISLOCATIONS
FINE STRUCTURE
FRACTURES
LAMELLAE
STRESSES
TWINNING