Microstructural characterization of near-[alpha] titanium alloy Ti-6Al-4Sn-4Zr-0. 70Nb-0. 50Mo-0. 40Si

Journal Article · Tue Jun 01 00:00:00 EDT 1993 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02668196· OSTI ID:6311701

Ramachandra, C; Singh, A K; Sarma, G M.K. ^[1]

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1. Baranas Hindu Univ., (India). Department of Metallurgical Engineering

Microstructural stability in the near-[alpha] titanium alloy (alloy 834) containing Ti-6Al-4Sn-4Zr-0.7ONb-0.5OMo-0.4OSi (in weight percent), in the [beta] and ([alpha] + [beta]) solution-treated and quenched conditions, has been investigated. The [beta] transus for this alloy is approximately 1,333 K. Solution treatment in the [beta] phase field at 1,353 K followed by quenching in water at room temperature resulted in the formation of [alpha][prime] martensite platelets with high dislocation density and stacking faults. Thin films of [beta] are found to be sandwiched between interface phases, which, in turn, are sandwiched at the interplatelet boundaries of lath martensite. The interface phase is a subject of much controversy in the literature. Solution treatment at 1,303 K in the ([alpha] + [beta]) phase field followed by quenching in water at room temperature resulted in the near-equiaxed primary a and transformed [beta]. Both the [beta] and ([alpha] + [beta]) solution-treated specimens were aged in the temperature range of 873 to 973 K. While aging the G-treated specimen at 973 K, ([alpha] + [beta])-treated specimen, even at a lower temperature of 873 K for 24 hours, caused precipitation of silicides predominantly at the interplatelet boundaries of martensite laths. Electron diffraction analysis confirmed them to be hexagonal silicide S[sub 2], with [alpha] = 0.702 nm and c = 0.36[sub 8] nm. The above difference in the precipitation could be attributed to the partitioning of a higher amount of [beta]- stabilizing elements as well as silicide-forming elements to the transformed [beta] in the ([alpha] + [beta]) solution-treated condition. However, ordering of the [alpha][prime] phase was observed under all of the aging conditions studied. The ordered domains were due to the longer aging times, which cause local increases in the level of the [alpha]-stabilizing elements.

• OSTI ID: 6311701
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Journal Name: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States) Vol. 24A:6; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
AGING
ALLOYS
ALUMINIUM ALLOYS
CARBON ADDITIONS
COHERENT SCATTERING
DIFFRACTION
ELECTRON DIFFRACTION
FILMS
HEAT TREATMENTS
INTERFACES
IRON ALLOYS
MARTENSITE
MICROSTRUCTURE
MOLYBDENUM ADDITIONS
MOLYBDENUM ALLOYS
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
PHASE STUDIES
PHASE TRANSFORMATIONS
PRECIPITATION
QUENCHING
SCATTERING
SEPARATION PROCESSES
SILICIDES
SILICON ADDITIONS
SILICON ALLOYS
SILICON COMPOUNDS
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
THIN FILMS
TIN ALLOYS
TITANIUM ALLOYS
TITANIUM BASE ALLOYS
ZIRCONIUM ALLOYS