Ti–U phases

7 phases (tier A 4, tier C 1, liquid 1, needs_review 1); 6 stable in a calculated diagram. Structure types are assigned only when the stored evidence supports an assignment under the stated tier rules (tier A: standard phase name; tier B: unique Materials Project + OQMD on-hull match, DFT-supported; tier C: one structure stated by the assessment's crystallographic table, assessor-stated); other phases list candidates and are marked needs_review. Stability is from phase diagrams calculated with pycalphad from the SGTE binary collection (evidence class: model).

Data: interactive registry · full JSON · Ti–U system page · Markdown · field reference

Phases of the Ti–U system (7)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
ORTHORHOMBIC_A20 phase:ti-u:a20-orthorhombic	alpha-U · A20 · oC4 · Cmcm (63)	tier A: standard phase name	stable in 3 of 3 calculated diagram(s): 300–1047.02 K, x(U) 0.98542–1	5	3
BCC_A2 phase:ti-u:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 3 of 3 calculated diagram(s): 909.91–1977.01 K, x(U) 0–1	11	3
FCC_A1 phase:ti-u:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	not stable in 3 calculated diagram(s)	0	3
HCP_A3 phase:ti-u:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	stable in 3 of 3 calculated diagram(s): 300–1221.93 K, x(U) 0–0.05428	3	3
LIQUID phase:ti-u:liquid	liquid	liquid	stable in 3 of 3 calculated diagram(s): 1052.74–4000 K, x(U) 0–1	1	3
TIU2 phase:ti-u:tiu2	Hg2U · hP3 · P6/mmm (191)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	stable in 3 of 3 calculated diagram(s): 300–1177.68 K, x(U) 0.66667–0.66667	17	3
TETRAGONAL_U phase:ti-u:u-tetragonal		needs_review	stable in 3 of 3 calculated diagram(s): 924.45–1406.46 K, x(U) 0.9747–1	9	3

ORTHORHOMBIC_A20 (Ti–U)

Id: phase:ti-u:a20-orthorhombic; status assigned
Structure: alpha-U · A20 · oC4 · Cmcm (63); type st:a20-alpha-u-oc4; tier A: standard phase name; confidence high
Stability: stable in 3 of 3 calculated diagram(s): 300–1047.02 K, x(U) 0.98542–1
Literature: 5 values (5 accepted) from 2 papers
Interactive: phase registry entry

Names (7): corpus: corpus:phase:ti-u:a20-orthorhombic, corpus:phase:ti-u:orthorhombic-a20
paper: paper:10.1016/j.jnucmat.2011.01.043:(α-U), paper:10.1016/j.jnucmat.2021.153317:αU
tdb: tdb:TiU-11Ber.tdb:ORTHORHOMBIC_A20, tdb:TiU-12Cao.tdb:ORTHORHOMBIC_A20, tdb:TiU-21Mo.tdb:ORTHORHOMBIC_A20

TDB models of ORTHORHOMBIC_A20 (3): PHASE and CONSTITUENT statements as written

TiU-11Ber.tdb: ORTHORHOMBIC_A20, type code %, sha256 305bf96c635dc687…

40: PHASE ORTHORHOMBIC_A20 % 1 1 !
41: CONST ORTHORHOMBIC_A20 : U : !

TiU-12Cao.tdb: ORTHORHOMBIC_A20, type code %, sha256 24682d23d60c12e4…

42: PHASE ORTHORHOMBIC_A20 % 1 1 !
43: CONST ORTHORHOMBIC_A20 : TI U% : !

TiU-21Mo.tdb: ORTHORHOMBIC_A20, type code %, sha256 0468f8a21aeadb99…

46: PHASE ORTHORHOMBIC_A20 % 1 1 !
47: CONST ORTHORHOMBIC_A20 : TI U% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2021.153317 Chuan Mo, Wenlin Mo, Baixue Bian, Peng Zhou, Yong Du, Tao Fa et al., Experimental investigation of the U-rich region and thermodynamic re-assessment of the U–Ti system, Journal of Nuclear Materials 557, 153317 (2021).
assessment that models this phase; reports values for this phase
doi:10.1016/j.jnucmat.2011.01.043 A. Berche, N. Dupin, C. Guéneau, C. Rado, B. Sundman, J.C. Dumas, Calphad thermodynamic description of some binary systems involving U, Journal of Nuclear Materials 411, 131-143 (2011).
assessment that models this phase; cited as the source of values for this phase; reports values for this phase

BCC_A2 (Ti–U)

Id: phase:ti-u:bcc-a2; status assigned
Structure: W · A2 · cI2 · Im-3m (229); type st:a2-w-ci2; tier A: standard phase name; confidence high
Stability: stable in 3 of 3 calculated diagram(s): 909.91–1977.01 K, x(U) 0–1
Literature: 11 values (11 accepted) from 2 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:ti-u:bcc-a2
paper: paper:10.1016/j.jnucmat.2011.01.043:bcc, paper:10.1016/j.jnucmat.2021.153317:γ(U,Ti)
tdb: tdb:TiU-11Ber.tdb:BCC_A2, tdb:TiU-12Cao.tdb:BCC_A2, tdb:TiU-21Mo.tdb:BCC_A2

TDB models of BCC_A2 (3): PHASE and CONSTITUENT statements as written

TiU-11Ber.tdb: BCC_A2, type code %B, sha256 305bf96c635dc687…

30: PHASE BCC_A2 %B 2 1 3 !
31: CONST BCC_A2 : TI U : VA : !

TiU-12Cao.tdb: BCC_A2, type code %B, sha256 24682d23d60c12e4…

32: PHASE BCC_A2 %B 2 1 3 !
33: CONST BCC_A2 : TI U : VA : !

TiU-21Mo.tdb: BCC_A2, type code %B, sha256 0468f8a21aeadb99…

36: PHASE BCC_A2 %B 2 1 3 !
37: CONST BCC_A2 : TI U : VA : !

Example references (3 of 3; assessments first):

doi:10.1016/j.jnucmat.2021.153317 Chuan Mo, Wenlin Mo, Baixue Bian, Peng Zhou, Yong Du, Tao Fa et al., Experimental investigation of the U-rich region and thermodynamic re-assessment of the U–Ti system, Journal of Nuclear Materials 557, 153317 (2021).
assessment that models this phase; reports values for this phase
doi:10.1016/j.jnucmat.2011.01.043 A. Berche, N. Dupin, C. Guéneau, C. Rado, B. Sundman, J.C. Dumas, Calphad thermodynamic description of some binary systems involving U, Journal of Nuclear Materials 411, 131-143 (2011).
assessment that models this phase; cited as the source of values for this phase; reports values for this phase
doi:10.1016/j.jnucmat.2011.08.050 S. Bajaj, A. Landa, P. Söderlind, P.E.A. Turchi, R. Arróyave, The U–Ti system: Strengths and weaknesses of the CALPHAD method, J. Nucl. Mater. 419 (1–3) (2011) 177–185.
cited as the source of values for this phase

FCC_A1 (Ti–U)

Id: phase:ti-u:fcc-a1; status assigned
Structure: Cu · A1 · cF4 · Fm-3m (225); type st:a1-cu-cf4; tier A: standard phase name; confidence high
Stability: not stable in 3 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:ti-u:fcc-a1
tdb: tdb:TiU-11Ber.tdb:FCC_A1, tdb:TiU-12Cao.tdb:FCC_A1, tdb:TiU-21Mo.tdb:FCC_A1

TDB models of FCC_A1 (3): PHASE and CONSTITUENT statements as written

TiU-11Ber.tdb: FCC_A1, type code %A, sha256 305bf96c635dc687…

25: PHASE FCC_A1 %A 2 1 1 !
26: CONST FCC_A1 : TI U : VA : !

TiU-12Cao.tdb: FCC_A1, type code %A, sha256 24682d23d60c12e4…

27: PHASE FCC_A1 %A 2 1 1 !
28: CONST FCC_A1 : TI U : VA : !

TiU-21Mo.tdb: FCC_A1, type code %A, sha256 0468f8a21aeadb99…

31: PHASE FCC_A1 %A 2 1 1 !
32: CONST FCC_A1 : TI U : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.01.043 A. Berche, N. Dupin, C. Guéneau, C. Rado, B. Sundman, J.C. Dumas, Calphad thermodynamic description of some binary systems involving U, Journal of Nuclear Materials 411, 131-143 (2011).
assessment that models this phase
doi:10.1016/j.jnucmat.2021.153317 Chuan Mo, Wenlin Mo, Baixue Bian, Peng Zhou, Yong Du, Tao Fa et al., Experimental investigation of the U-rich region and thermodynamic re-assessment of the U–Ti system, Journal of Nuclear Materials 557, 153317 (2021).
assessment that models this phase

HCP_A3 (Ti–U)

Id: phase:ti-u:hcp-a3; status assigned
Structure: Mg · A3 · hP2 · P6_3/mmc (194); type st:a3-mg-hp2; tier A: standard phase name; confidence high
Stability: stable in 3 of 3 calculated diagram(s): 300–1221.93 K, x(U) 0–0.05428
Literature: 3 values (3 accepted) from 2 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:ti-u:hcp-a3
paper: paper:10.1016/j.jnucmat.2011.01.043:hcp, paper:10.1016/j.jnucmat.2021.153317:αTi
tdb: tdb:TiU-11Ber.tdb:HCP_A3, tdb:TiU-12Cao.tdb:HCP_A3, tdb:TiU-21Mo.tdb:HCP_A3

TDB models of HCP_A3 (3): PHASE and CONSTITUENT statements as written

TiU-11Ber.tdb: HCP_A3, type code %A, sha256 305bf96c635dc687…

35: PHASE HCP_A3 %A 2 1 0.5 !
36: CONST HCP_A3 : TI% U : VA : !

TiU-12Cao.tdb: HCP_A3, type code %A, sha256 24682d23d60c12e4…

37: PHASE HCP_A3 %A 2 1 0.5 !
38: CONST HCP_A3 : TI% U : VA : !

TiU-21Mo.tdb: HCP_A3, type code %A, sha256 0468f8a21aeadb99…

41: PHASE HCP_A3 %A 2 1 0.5 !
42: CONST HCP_A3 : TI% U : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.01.043 A. Berche, N. Dupin, C. Guéneau, C. Rado, B. Sundman, J.C. Dumas, Calphad thermodynamic description of some binary systems involving U, Journal of Nuclear Materials 411, 131-143 (2011).
assessment that models this phase; cited as the source of values for this phase; reports values for this phase
doi:10.1016/j.jnucmat.2021.153317 Chuan Mo, Wenlin Mo, Baixue Bian, Peng Zhou, Yong Du, Tao Fa et al., Experimental investigation of the U-rich region and thermodynamic re-assessment of the U–Ti system, Journal of Nuclear Materials 557, 153317 (2021).
assessment that models this phase; reports values for this phase

LIQUID (Ti–U)

Id: phase:ti-u:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 3 of 3 calculated diagram(s): 1052.74–4000 K, x(U) 0–1
Literature: 1 values (1 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:ti-u:liquid
paper: paper:10.1016/j.jnucmat.2011.01.043:L
tdb: tdb:TiU-11Ber.tdb:LIQUID, tdb:TiU-12Cao.tdb:LIQUID, tdb:TiU-21Mo.tdb:LIQUID

TDB models of LIQUID (3): PHASE and CONSTITUENT statements as written

TiU-11Ber.tdb: LIQUID, type code %, sha256 305bf96c635dc687…

20: PHASE LIQUID:L % 1 1 !
21: CONST LIQUID:L : TI U : !

TiU-12Cao.tdb: LIQUID, type code %, sha256 24682d23d60c12e4…

22: PHASE LIQUID:L % 1 1 !
23: CONST LIQUID:L : TI U : !

TiU-21Mo.tdb: LIQUID, type code %, sha256 0468f8a21aeadb99…

26: PHASE LIQUID:L % 1 1 !
27: CONST LIQUID:L : TI U : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2011.01.043 A. Berche, N. Dupin, C. Guéneau, C. Rado, B. Sundman, J.C. Dumas, Calphad thermodynamic description of some binary systems involving U, Journal of Nuclear Materials 411, 131-143 (2011).
assessment that models this phase; reports values for this phase
doi:10.1016/j.jnucmat.2021.153317 Chuan Mo, Wenlin Mo, Baixue Bian, Peng Zhou, Yong Du, Tao Fa et al., Experimental investigation of the U-rich region and thermodynamic re-assessment of the U–Ti system, Journal of Nuclear Materials 557, 153317 (2021).
assessment that models this phase

TIU2 (Ti–U)

Id: phase:ti-u:tiu2; status assigned
Structure: Hg2U · hP3 · P6/mmm (191); type st:hg2u-hp3; tier C: assessor-stated (Hallstedt 2025 crystallographic table); confidence assessor-stated
Structure source: B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, supplementary crystallographic table (mmc2) doi:10.1016/j.calphad.2025.102833
Caveat: not certain from the name or DFT alone (dft_space_group_191_matches_2_structure_types, no_structure_token); structure as stated in the SGTE crystallographic table for this phase name and system
Stoichiometry: Ti 0.3333, U 0.6667
Stability: stable in 3 of 3 calculated diagram(s): 300–1177.68 K, x(U) 0.66667–0.66667
Literature: 17 values (17 accepted) from 2 papers
Interactive: phase registry entry

Names (6): corpus: corpus:phase:ti-u:tiu2
paper: paper:10.1016/j.jnucmat.2011.01.043:U2Ti, paper:10.1016/j.jnucmat.2021.153317:δ-U2Ti
tdb: tdb:TiU-11Ber.tdb:TIU2, tdb:TiU-12Cao.tdb:TIU2, tdb:TiU-21Mo.tdb:TIU2

TDB models of TIU2 (3): PHASE and CONSTITUENT statements as written

TiU-11Ber.tdb: TIU2, type code %, sha256 305bf96c635dc687…

50: PHASE TIU2 % 2 1 2 !
51: CONST TIU2 : TI : U : !

TiU-12Cao.tdb: TIU2, type code %, sha256 24682d23d60c12e4…

52: PHASE TIU2 % 2 1 2 !
53: CONST TIU2 : TI : U : !

TiU-21Mo.tdb: TIU2, type code %, sha256 0468f8a21aeadb99…

56: PHASE TIU2 % 2 1 2 !
57: CONST TIU2 : TI : U : !

Example references (3 of 3; assessments first):

doi:10.1016/j.jnucmat.2021.153317 Chuan Mo, Wenlin Mo, Baixue Bian, Peng Zhou, Yong Du, Tao Fa et al., Experimental investigation of the U-rich region and thermodynamic re-assessment of the U–Ti system, Journal of Nuclear Materials 557, 153317 (2021).
assessment that models this phase; reports values for this phase
doi:10.1016/j.jnucmat.2011.01.043 A. Berche, N. Dupin, C. Guéneau, C. Rado, B. Sundman, J.C. Dumas, Calphad thermodynamic description of some binary systems involving U, Journal of Nuclear Materials 411, 131-143 (2011).
assessment that models this phase; cited as the source of values for this phase; reports values for this phase
doi:10.1016/j.jnucmat.2011.08.050 S. Bajaj, A. Landa, P. Söderlind, P.E.A. Turchi, R. Arróyave, The U–Ti system: Strengths and weaknesses of the CALPHAD method, J. Nucl. Mater. 419 (1–3) (2011) 177–185.
cited as the source of values for this phase

TETRAGONAL_U (Ti–U)

Id: phase:ti-u:u-tetragonal; status needs_review
No structure assigned. Why: name_has_descriptive_tokens:TETRAGONAL; no_structure_token
Candidate (sgte_mmc2): beta-U · A_b · tP30 · P4_2/mnm (136) — Hallstedt 2025 mmc2 row for TETRAGONAL_U: beta-U
Candidate (tdb_comment): beta-U · tP30 · P4_2/mnm, SB: A_b — TiU-11Ber.tdb: 'Prototype beta-U (tP30, P4_2/mnm, SB: A_b)'
Candidate (tdb_comment): beta-U · tP30 · P4_2/mnm, SB: A_b — TiU-12Cao.tdb: 'Prototype beta-U (tP30, P4_2/mnm, SB: A_b)'
Candidate (tdb_comment): beta-U · tP30 · P4_2/mnm, SB: A_b — TiU-21Mo.tdb: 'Prototype beta-U (tP30, P4_2/mnm, SB: A_b)'
Stability: stable in 3 of 3 calculated diagram(s): 924.45–1406.46 K, x(U) 0.9747–1
Literature: 9 values (9 accepted) from 2 papers
Interactive: phase registry entry

Names (7): corpus: corpus:phase:ti-u:u-tetragonal, corpus:phase:ti-u:tetragonal-u
paper: paper:10.1016/j.jnucmat.2011.01.043:(β-U), paper:10.1016/j.jnucmat.2021.153317:βU
tdb: tdb:TiU-11Ber.tdb:TETRAGONAL_U, tdb:TiU-12Cao.tdb:TETRAGONAL_U, tdb:TiU-21Mo.tdb:TETRAGONAL_U

TDB models of TETRAGONAL_U (3): PHASE and CONSTITUENT statements as written

TiU-11Ber.tdb: TETRAGONAL_U, type code %, sha256 305bf96c635dc687…

45: PHASE TETRAGONAL_U % 1 1 !
46: CONST TETRAGONAL_U : TI U% : !

TiU-12Cao.tdb: TETRAGONAL_U, type code %, sha256 24682d23d60c12e4…

47: PHASE TETRAGONAL_U % 1 1 !
48: CONST TETRAGONAL_U : TI U% : !

TiU-21Mo.tdb: TETRAGONAL_U, type code %, sha256 0468f8a21aeadb99…

51: PHASE TETRAGONAL_U % 1 1 !
52: CONST TETRAGONAL_U : TI U% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2021.153317 Chuan Mo, Wenlin Mo, Baixue Bian, Peng Zhou, Yong Du, Tao Fa et al., Experimental investigation of the U-rich region and thermodynamic re-assessment of the U–Ti system, Journal of Nuclear Materials 557, 153317 (2021).
assessment that models this phase; reports values for this phase
doi:10.1016/j.jnucmat.2011.01.043 A. Berche, N. Dupin, C. Guéneau, C. Rado, B. Sundman, J.C. Dumas, Calphad thermodynamic description of some binary systems involving U, Journal of Nuclear Materials 411, 131-143 (2011).
assessment that models this phase; cited as the source of values for this phase; reports values for this phase

Please cite

R. Arróyave, J. Saal, D. Shin, ORCHID-Registry: phase registry of binary systems (version 2026.10; Version 1, machine-extracted), Zenodo (2026). doi:10.5281/zenodo.23735970
R. Arróyave, J. Saal, D. Shin, ORCHID data: umbrella record of the ORCHID datasets (version 2026.10; Version 1, machine-extracted), Zenodo (2026). doi:10.5281/zenodo.23736065

Also cite B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, https://doi.org/10.1016/j.calphad.2025.102833 (CC BY 4.0), and the original assessment named in each file; A. Jain et al., The Materials Project: A materials genome approach to accelerating materials innovation, APL Materials 1 (2013) 011002, https://doi.org/10.1063/1.4812323 (CC BY 4.0); J. E. Saal et al., JOM 65 (2013) 1501, https://doi.org/10.1007/s11837-013-0755-4 and S. Kirklin et al., npj Comput. Mater. 1 (2015) 15010, https://doi.org/10.1038/npjcompumats.2015.10 (CC BY 4.0); the original source of every value you use (paper_citation / paper_doi, and cited_dois for values the paper cites from earlier work). Version 1, machine-extracted: values were read by language-model readers constrained to quote their source and checked automatically, and the release was then audited on the printed pages by adversarial audits, an independent second review of fit-facing records and a preliminary human review of a frozen sample. Flags such as accepted and ESPEI-ready record screening results, not certification; known issues are listed in the release notes.

@misc{orchid_phase_registry_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Registry: phase registry of binary systems}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735970},
  url       = {https://doi.org/10.5281/zenodo.23735970},
  note      = {Version 1, machine-extracted}
}

@misc{orchid_data_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID data: umbrella record of the ORCHID datasets}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23736065},
  url       = {https://doi.org/10.5281/zenodo.23736065},
  note      = {Version 1, machine-extracted}
}