Alloying-Driven Phase Stability in Group-VB Transition Metals under Compression

ABSTRACTThe change in phase stability of Group-VB (V, Nb, and Ta) transition metals due to pressure and alloying is explored by means of first-principles electronic-structure calculations. It is shown that under compression stabilization or destabilization of the ground-state body-centered cubic (bcc) phase of the metal is mainly dictated by the band-structure energy that correlates well with the position of the Kohn anomaly in the transverse acoustic phonon mode. The predicted position of the Kohn anomaly in V, Nb, and Ta is found to be in a good agreement with data from the inelastic x-ray or neutron scattering measurements. In the case of alloying the change in phase stability is defined by the interplay between the band-structure and Madelung energies. We show that band-structure effects determine phase stability when a particular Group-VB metal is alloyed with its nearest neighbors within the same d-transition series: the neighbor with less and more d electrons destabilize and stabilize the bcc phase, respectively. When V is alloyed with neighbors of a higher (4d- or 5d-) transition series, both electrostatic Madelung and band-structure energies stabilize the body-centered-cubic phase. The opposite effect (destabilization) happens when Nb or Ta is alloyed with neighbors of the 3d-transition series.

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Alloying-Driven Phase Stability in Group-VB Transition Metals under Compression

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.258.125 ◽

2016 ◽

Vol 258 ◽

pp. 125-130

Author(s):

Alexander Landa ◽

Per Söderlind

Keyword(s):

Transition Metals ◽

Band Structure ◽

Phase Stability ◽

Elevated Pressure ◽

Mechanical Instability ◽

Transition Series ◽

Band Structure Energy ◽

Bcc Phase ◽

Structure Calculations ◽

State Body

The change in phase stability of Group-VB transition metals (V, Nb, and Ta) due to pressure and alloying is explored by means of first-principles electronic-structure calculations. It is shown that under compression stabilization or destabilization of the ground-state body-centered cubic (bcc) phase of the metal is mainly dictated by the band-structure energy. In the case of alloying the change in phase stability is defined by the interplay between the band-structure and Madelung energies. We show that band-structure effects determine phase stability when a particular Group-VB metal is alloyed with its nearest neighbors within the same d-transition series: the neighbor with less and more d electrons destabilize and stabilize the bcc phase, respectively. When V is alloyed with neighbors of a higher (4d- or 5d-) transition series, both electrostatic Madelung and band-structure energies stabilize the bcc phase. Utilizing the self-consistent ab initio lattice dynamics approach, we show that pressure-induced mechanical instability of bcc V, which results in formation of a rhombohedral (rh) phase at around 60-70 GPa at room temperatures, will prevail significant heating and compression. Furthermore, alloying with Cr decreases the temperature at which stabilization of the bcc phase occurs at elevated pressure.

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Phase equilibria and phase transformation of the body-centered cubic phase in the Cu-rich portion of the Cu–Ti–Al system

Journal of Materials Research ◽

10.1557/jmr.2008.0334 ◽

2008 ◽

Vol 23 (10) ◽

pp. 2674-2684 ◽

Cited By ~ 6

Author(s):

X.J. Liu ◽

C.P. Wang ◽

I. Ohnuma ◽

R. Kainuma ◽

K. Ishida

Keyword(s):

Phase Transformation ◽

Phase Equilibria ◽

Al Alloys ◽

The Body ◽

Miscibility Gap ◽

Cubic Phase ◽

Face Centered Cubic ◽

Body Centered Cubic ◽

Metallographic Examination ◽

Bcc Phase

The phase equilibria and phase transformation of the body-centered cubic (bcc) phase in the Cu–Ti–Al system were investigated by the diffusion couple method, metallographic examination, differential scanning calorimetry, and x-ray diffraction. The isothermal sections at 700 and 900 °C and vertical sections at 18 at.% Al, 22 at.% Al, and 25 at.% Al in the Cu-rich portion were determined. These results indicate that (i) the Cu2TiAl compound with the L21 Heusler structure has a larger solubility range; (ii) the stable B2 + L21 miscibility gap of the ordered bcc phase exists until the liquid phase, and the tie lines of this miscibility gap are almost parallel with the Cu–Ti side; (iii) the composition and temperature for the eutectic reaction (L ↔ B2 + L21) are about 7 at.% Ti and about 970 °C, respectively, and (iv) the velocity of the eutectoid decomposition [bcc ↔ face-centered cubic (fcc) + D83] of the bcc phase with martensitic morphology in the Cu–Ti–Al alloys is slower than that of the Cu–Al alloys.

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Rapid Thermal Transformation of A-15 Crystal Structure Metallic Thin Films

MRS Proceedings ◽

10.1557/proc-387-377 ◽

1995 ◽

Vol 387 ◽

Cited By ~ 2

Author(s):

M. J. O'Keefe ◽

C. L. Cerny

Keyword(s):

Crystal Structure ◽

Thin Films ◽

Thermal Annealing ◽

Rapid Thermal Annealing ◽

Physical Vapor Deposition ◽

Thermal Transformation ◽

The Body ◽

Cubic Phase ◽

Body Centered Cubic ◽

Body Center Cubic

AbstractPhysical vapor deposition of Group VI elements (Cr, Mo, W) can lead to the formation of a metastable A-15 crystal structure under certain processing conditions. Typically, a thermally induced transformation of the metastable A-15 structure into the equilibrium body centered cubic structure has been accomplished by conventional furnace annealing at T/Tm ≈ 0.3 from tens of minutes to several hours. In this study we report on the use of rapid thermal annealing to transform sputter deposited A- 15 crystal structure tungsten and chromium thin films into body centered cubic films within the same temperature range but at times on the order of one minute. The minimum annealing times and temperatures required for complete transformation of the A-15 phase into the BCC phase varied from sample to sample, indicating that the transformation was dependent on the film characteristics. The electrical resistivity of A-15 Cr and W films was measured before and after rapid thermal annealing and was found to significantly decrease after transformation into the body center cubic phase.

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Textures of the Hot-Forged Ti6Al4V Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.203-204.111 ◽

2013 ◽

Vol 203-204 ◽

pp. 111-114

Author(s):

Adam Bunsch ◽

Wiktoria Ratuszek ◽

Małgorzata Witkowska ◽

Joanna Kowalska ◽

Aneta Łukaszek-Sołek

Keyword(s):

Deformation Temperature ◽

Phase State ◽

Hexagonal Phase ◽

Ti6al4v Alloy ◽

The Body ◽

Cubic Phase ◽

Body Centered Cubic ◽

Two Phase ◽

Different Temperatures

This paper presents the results of the texture investigation in the hexagonal phase and the body-centered cubic  phase of the Ti6Al4V alloy hot-deformed by forging. Forging was performed at two different temperatures on the occurrence of the single  and in the two-phase  +  state. It was found that after deformation both  and  phases are textured and their textures strongly depends on deformation temperature.

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ω Transformation in cold-worked Ti–Nb–Ta–Zr–O alloys with low body-centered cubic phase stability and its correlation with their elastic properties

Acta Materialia ◽

10.1016/j.actamat.2012.09.041 ◽

2013 ◽

Vol 61 (1) ◽

pp. 139-150 ◽

Cited By ~ 59

Author(s):

M. Tane ◽

T. Nakano ◽

S. Kuramoto ◽

M. Niinomi ◽

N. Takesue ◽

...

Keyword(s):

Elastic Properties ◽

Phase Stability ◽

Cubic Phase ◽

Body Centered Cubic ◽

Cold Worked

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Shear-Induced Orientational Transitions in the Body-Centered Cubic Phase of a Diblock Copolymer Gel

Macromolecules ◽

10.1021/ma971561m ◽

1998 ◽

Vol 31 (12) ◽

pp. 3906-3911 ◽

Cited By ~ 40

Author(s):

I. W. Hamley ◽

J. A. Pople ◽

J. P. A. Fairclough ◽

A. J. Ryan ◽

C. Booth ◽

...

Keyword(s):

Diblock Copolymer ◽

The Body ◽

Cubic Phase ◽

Body Centered Cubic ◽

Orientational Transitions

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Critical factors that determine face-centered cubic to body-centered cubic phase transformation in sputter-deposited austenitic stainless steel films

Journal of Materials Research ◽

10.1557/jmr.2004.0215 ◽

2004 ◽

Vol 19 (6) ◽

pp. 1696-1702 ◽

Cited By ~ 12

Author(s):

X. Zhang ◽

A. Misra ◽

R.K. Schulze ◽

C.J. Wetteland ◽

H. Wang ◽

...

Keyword(s):

Thin Films ◽

Stainless Steel ◽

Austenitic Stainless Steel ◽

Phase Stability ◽

Cubic Phase ◽

Face Centered Cubic ◽

Body Centered Cubic ◽

Bcc Structure ◽

Face Centered ◽

Sputter Deposited

Bulk austenitic stainless steels (SS) have a face-centered cubic (fcc) structure. However, sputter deposited films synthesized using austenitic stainless steel targets usually exhibit body-centered cubic (bcc) structure or a mixture of fcc and bcc phases. This paper presents studies on the effect of processing parameters on the phase stability of 304 and 330 SS thin films. The 304 SS thin films with in-plane, biaxial residual stresses in the range of approximately 1 GPa (tensile) to approximately 300 MPa (compressive) exhibited only bcc structure. The retention of bcc 304 SS after high-temperature annealing followed by slow furnace cooling indicates depletion of Ni in as-sputtered 304 SS films. The 330 SS films sputtered at room temperature possess pure fcc phase. The Ni content and the substrate temperature during deposition are crucial factors in determining the phase stability in sputter deposited austenitic SS films.

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