Effect of Extrusion Temperature on the Microstructural Development of Powder Metallurgy Ti-47A1-2Cr-1Nb-1Ta Alloy
Conference
·
OSTI ID:792726
- LLNL
Effect of extrusion temperatures on the microstructural development of a powder metallurgy (PM) Ti-47Al-2Cr-1Nb-1Ta (at. %) alloy has been investigated. Microstructure of the PM alloy extruded at 1150 C consists of a fine-grained ({gamma} + {alpha}{sub 2}) two-phase structure in association with coarse grains of metastable B2 (ordered bcc) phase. In addition, fine {omega} (ordered hexagonal) particles are also found within some B2 grains. The PM alloy containing the metastable B2 grains displays a low-temperature superplastic behavior, in which a tensile elongation of 310% is obtained at 800 C under a strain rate of 2 x 10{sup -5} s{sup -1}. It is suggested that the decomposition of metastable B2 phase and microstructural evolution during the deformation play a crucial role in the low-temperature superplasticity of the PM TiAl alloy. A refined fully-lamellar (FL) microstructure with alternating {gamma} and {alpha}{sub 2} lamellae is developed within the PM alloy extruded at 1400 C. The creep resistance of the refined FL-TiAl alloy is found to be superior to those of the TiAl alloys fabricated by conventional processing techniques. Creep mechanisms for the PM alloy with a refined FL microstructure are critically discussed according to TEM examination of deformation substructure.
- 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:
- 792726
- Report Number(s):
- UCRL-JC-137615
- Country of Publication:
- United States
- Language:
- English
Similar Records
The role of ledges in creep of TiAl alloys with fine lamellar structures
Development of ultrafine lamellar structures in two-phase {gamma}-TiAl alloys
Stability of ultrafine lamellar structures during aging in two-phase {gamma}-TiAl alloys
Journal Article
·
Sun Mar 22 23:00:00 EST 1998
· Acta Materialia
·
OSTI ID:616244
Development of ultrafine lamellar structures in two-phase {gamma}-TiAl alloys
Journal Article
·
Wed Dec 31 23:00:00 EST 1997
· Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
·
OSTI ID:605814
Stability of ultrafine lamellar structures during aging in two-phase {gamma}-TiAl alloys
Conference
·
Fri Aug 01 00:00:00 EDT 1997
·
OSTI ID:516994