An investigation of the ‘omega-phase’ in Ni-rich Ni-Al

Metastable beta titanium alloys have been known to have numerous advantages such as cold formability, high strength, good fracture resistance, deep hardenability, and cost effectiveness. Very high strength is obtainable by precipitation of the hexagonal alpha phase in a bcc beta matrix in these alloys. Precipitation hardening in the metastable beta alloys may also result from the formation of transition phases such as omega phase. Ti-15-3 (Ti-15V- 3Cr-3Al-3Sn) has been developed recently by TIMET and USAF for low cost sheet metal applications. The purpose of the present study was to examine the aging characteristics in this alloy.The composition of the as-received material is: 14.7 V, 3.14 Cr, 3.05 Al, 2.26 Sn, and 0.145 Fe. The beta transus temperature as determined by optical metallographic method was about 770°C. Specimen coupons were prepared from a mill-annealed 1.2 mm thick sheet, and solution treated at 827°C for 2 hr in argon, then water quenched. Aging was also done in argon at temperatures ranging from 316 to 616°C for various times.

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Omega phase formation in RMI (38-6-44) beta titanium alloy

Journal of Materials Science ◽

10.1007/bf00737852 ◽

1974 ◽

Vol 9 (3) ◽

pp. 487-490 ◽

Cited By ~ 7

Author(s):

Gordon A. Sargent ◽

H. Huang ◽

R. J. De Angelis

Keyword(s):

Titanium Alloy ◽

Phase Formation ◽

Omega Phase ◽

Beta Titanium Alloy ◽

Beta Titanium

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Omega-phase in Ti-Hf-Zr alloys produced by the hydride-cycle methodSpecial issue on Neutron Scattering in Canada.

Canadian Journal of Physics ◽

10.1139/p10-025 ◽

2010 ◽

Vol 88 (10) ◽

pp. 741-749 ◽

Cited By ~ 4

Author(s):

Ian P. Swainson ◽

Seda K. Dolukanyan ◽

Anahit G. Aleksanyan ◽

Veniamin Sh. Shekhtman ◽

Davit G. Mayilyan ◽

...

Keyword(s):

Phase Transition ◽

Omega Phase ◽

Interstitial Solid Solution ◽

Concentration Triangle ◽

X Ray ◽

Ω Phase ◽

Step Model ◽

Temperature And Pressure ◽

Potential Sign ◽

Zr Alloys

We report the presence of large proportions of ω-phase in Ti-Hf-Zr alloys, prepared using the hydride cycle technique. We show that the ω-phase extends across the concentration triangle of Ti-Zr-Hf and report the partitioning of the three metals across the two sites in this structure from neutron and X-ray data. We examine the symmetry of the order parameter governing the β–ω phase transition and show that a two-step model for the phase transition involving site ordering followed by displacement is not likely to be correct. We suggest that an interstitial solid solution of oxygen and octahedral vacancies exists, and that the observation of any ω-phase diffraction pattern of alloys of these metals at ambient temperature and pressure should be viewed as a potential sign of the presence of oxygen in the octahedral interstitial sites.

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Ultrasonic study of the beta → omega phase transformation in Zr-Nb alloys

Acta Metallurgica ◽

10.1016/0001-6160(72)90101-0 ◽

1972 ◽

Vol 20 (5) ◽

pp. 725-733 ◽

Cited By ~ 39

Author(s):

G Goasdoue ◽

P.S Ho ◽

S.L Sass

Keyword(s):

Phase Transformation ◽

Omega Phase ◽

Ultrasonic Study

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In-situ Experiments to Capture the Evolution of Microstructure During Phase Transformation of Titanium Under Dynamic Loading

EPJ Web of Conferences ◽

10.1051/epjconf/201818303020 ◽

2018 ◽

Vol 183 ◽

pp. 03020

Author(s):

Benjamin M. Morrow ◽

David R. Jones ◽

Paulo A. Rigg ◽

George T. Gray ◽

Ellen K. Cerreta

Keyword(s):

Phase Transformation ◽

Dynamic Loading ◽

Microstructural Analysis ◽

Alpha Phase ◽

Material Behavior ◽

High Rate ◽

Omega Phase ◽

In Situ Experiments ◽

Consistent Picture ◽

Underlying Mechanisms

Under sufficient stresses, such as during dynamic loading, titanium experiences a phase transformation from hcp alpha phase to hexagonal omega phase. Omega phase is often retained in the microstructure after unloading, and has a strong influence on subsequent mechanical properties. Simulations suggest there are multiple pathways and underlying mechanisms for this transformation. Due to the incredibly short timescales involved, experimental measurements for model validation have been difficult. However, new capabilities at the Advanced Photon Source have enabled diffraction measurements during plate impact experiments to study the evolution of titanium during transformation. These high-rate data allow us to probe the mechanism and kinetics of phase transformations in new ways. Recent results will be presented and compared to post-mortem characterization of soft-recovered shocked specimens. Comparisons are made with previous tests where material was shock-loaded and soft recovered for microstructural analysis. Together these techniques create a consistent picture of material behavior during the shock-induced ff–! phase transformation in titanium.

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