{
  "spore": "profile",
  "id": "titanium-aluminide",
  "spore_version": "0.2",
  "family": "titanium-alloys",
  "name": "Gamma titanium aluminide (TiAl), Ti-48Al-2Cr-2Nb turbine-blade alloy",
  "abbreviation": "TiAl",
  "role": "high-temperature structural intermetallic",
  "category": "metals",
  "type": "titanium",
  "summary": "Gamma titanium aluminide (gamma TiAl) is an intermetallic compound of titanium and about 48 at. % aluminium, usually with small chromium and niobium additions. It is not a conventional titanium alloy. NASA gives its density as 3.8 g/cm3 for the gamma family. Cast to size, the Ti-48Al-2Cr-2Nb alloy has a room-temperature 0.2 % offset yield strength of 326 MPa, a tensile strength of 422 MPa and only 1.70 % elongation. GE manufactured and engine-tested low-pressure turbine blades from this alloy in 1993, and uses TiAl low-pressure turbine blades in its GEnx and LEAP engines. Low room-temperature ductility is the main limit.\n",
  "best_for": "Light rotating parts that run hot, such as low-pressure turbine blades in GE engines, where a density near 3.8 g/cm3 and a stiffness of 168 GPa matter more than ductility",
  "weakest_at": "Room-temperature ductility, since cast Ti-48-2-2 elongates only 1.70 % at 23 degC and impact can crack thin sections",
  "identity": {
    "formula": "Ti-48Al-2Cr-2Nb (at. %): gamma TiAl with 2 at. % Cr and 2 at. % Nb. The alpha-2 class is Ti3Al",
    "cas": "",
    "designations": [],
    "source": "nasa-2004",
    "where": "Introduction and Materials sections: Ti-48Al-2Cr-2Nb (at.%) is the GEAE low-pressure turbine blade alloy"
  },
  "tags": {
    "environments": [],
    "stresses": [],
    "applications": [
      "propulsion-and-tanks",
      "structures"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, gamma TiAl family",
      "value": 3.8,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "gamma TiAl alloy family, as printed in the report introduction (not one composition)"
      },
      "method": "Value printed in the introduction of NASA TM 2004-212303",
      "status": "ground",
      "source": "nasa-2004",
      "where": "Introduction, first paragraphs (the sentence giving low density (3.8 g/cm3))",
      "source_detail": {
        "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
        "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
        "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
        "year": 2004,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, gamma class",
      "value": 4.04,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "gamma class (gamma plus alpha-2 two-phase alloys) column of Table I"
      },
      "method": "Value printed in a comparison table of titanium aluminides, titanium alloys and superalloys (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Density g/cm3 row, Gamma column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, alpha-2 class (Ti3Al based)",
      "value": 4.84,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "alpha-2 class (alpha-2 plus beta alloys) column of Table I"
      },
      "method": "Value printed in a comparison table of titanium aluminides, titanium alloys and superalloys (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Density g/cm3 row, Alpha-2 column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, titanium alloy class (for comparison, not TiAl)",
      "value": 4.54,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "Ti alloys column of Table I, class average for comparison"
      },
      "method": "Value printed in a comparison table (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Density g/cm3 row, Ti Alloys column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, superalloy class (for comparison)",
      "value": 8.3,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "Superalloys column of Table I, class average for comparison"
      },
      "method": "Value printed in a comparison table (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Density g/cm3 row, Superalloys column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Elastic modulus, cast-to-size Ti-48-2-2, 23 degC",
      "value": 168,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "alloy": "Ti-48Al-2Cr-2Nb cast to size",
        "temperature": "23 degC",
        "test": "tabulated average; method not printed in the table"
      },
      "method": "Average elastic modulus printed in the tensile property table of NASA TM 2004-212303",
      "status": "ground",
      "source": "nasa-2004",
      "where": "Table VII, Average tensile properties for gamma TiAl alloys, Cast-to-size Ti-48-2-2 row, 23 degC, Elastic modulus column",
      "source_detail": {
        "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
        "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
        "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
        "year": 2004,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Elastic modulus, cast-to-size Ti-48-2-2, 650 degC",
      "value": 141,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "alloy": "Ti-48Al-2Cr-2Nb cast to size",
        "temperature": "650 degC",
        "test": "tabulated average; method not printed in the table"
      },
      "method": "Average elastic modulus printed in the tensile property table of NASA TM 2004-212303",
      "status": "ground",
      "source": "nasa-2004",
      "where": "Table VII, Cast-to-size Ti-48-2-2 row, 650 degC, Elastic modulus column",
      "source_detail": {
        "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
        "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
        "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
        "year": 2004,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Stiffness, gamma class",
      "value": 176,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "basis": "gamma class (gamma plus alpha-2 two-phase alloys), class value from Table I"
      },
      "method": "Value printed in a comparison table (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Stiffness GPa row, Gamma column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Stiffness, alpha-2 class (Ti3Al based)",
      "value": 145,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "basis": "alpha-2 class (alpha-2 plus beta alloys), class value from Table I"
      },
      "method": "Value printed in a comparison table (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Stiffness GPa row, Alpha-2 column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Stiffness, titanium alloy class (for comparison)",
      "value": 110,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "basis": "Ti alloys column of Table I, class value for comparison"
      },
      "method": "Value printed in a comparison table (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Stiffness GPa row, Ti Alloys column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Stiffness, superalloy class (for comparison)",
      "value": 207,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "basis": "Superalloys column of Table I, class value for comparison"
      },
      "method": "Value printed in a comparison table (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Stiffness GPa row, Superalloys column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "yield_strength",
      "label": "0.2 % yield strength, cast-to-size Ti-48-2-2, 23 degC",
      "value": 326,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "alloy": "Ti-48Al-2Cr-2Nb cast to size",
        "temperature": "23 degC",
        "offset": "0.2 %"
      },
      "method": "Average printed in the tensile property table of NASA TM 2004-212303",
      "status": "ground",
      "source": "nasa-2004",
      "where": "Table VII, Cast-to-size Ti-48-2-2 row, 23 degC, Yield strength column",
      "source_detail": {
        "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
        "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
        "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
        "year": 2004,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "yield_strength",
      "label": "0.2 % yield strength, cast-to-size Ti-48-2-2, 650 degC",
      "value": 284,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "alloy": "Ti-48Al-2Cr-2Nb cast to size",
        "temperature": "650 degC",
        "offset": "0.2 %"
      },
      "method": "Average printed in the tensile property table of NASA TM 2004-212303",
      "status": "ground",
      "source": "nasa-2004",
      "where": "Table VII, Cast-to-size Ti-48-2-2 row, 650 degC, Yield strength column",
      "source_detail": {
        "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
        "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
        "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
        "year": 2004,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, cast-to-size Ti-48-2-2, 23 degC",
      "value": 422,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "alloy": "Ti-48Al-2Cr-2Nb cast to size",
        "temperature": "23 degC"
      },
      "method": "Average printed in the tensile property table of NASA TM 2004-212303",
      "status": "ground",
      "source": "nasa-2004",
      "where": "Table VII, Cast-to-size Ti-48-2-2 row, 23 degC, Tensile strength column",
      "source_detail": {
        "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
        "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
        "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
        "year": 2004,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, cast-to-size Ti-48-2-2, 650 degC",
      "value": 474,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "alloy": "Ti-48Al-2Cr-2Nb cast to size",
        "temperature": "650 degC"
      },
      "method": "Average printed in the tensile property table of NASA TM 2004-212303",
      "status": "ground",
      "source": "nasa-2004",
      "where": "Table VII, Cast-to-size Ti-48-2-2 row, 650 degC, Tensile strength column",
      "source_detail": {
        "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
        "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
        "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
        "year": 2004,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, GE gamma alloy, room temperature",
      "value": 620,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "basis": "gamma alloys developed at GE, best typical values in Table II (alloy not named)",
        "temperature": "23 degC",
        "elongation": "3 %"
      },
      "method": "Value printed in a table of recent property highlights (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table II, Gamma column, first row",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, GE gamma alloy, 760 degC",
      "value": 550,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "basis": "gamma alloys developed at GE, Table II (alloy not named)",
        "temperature": "760 degC"
      },
      "method": "Value printed in a table of recent property highlights (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table II, Gamma column, second row",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "elongation",
      "label": "Elongation, cast-to-size Ti-48-2-2, 23 degC",
      "value": 1.7,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "alloy": "Ti-48Al-2Cr-2Nb cast to size",
        "temperature": "23 degC"
      },
      "method": "Average printed in the tensile property table of NASA TM 2004-212303",
      "status": "ground",
      "source": "nasa-2004",
      "where": "Table VII, Cast-to-size Ti-48-2-2 row, 23 degC, Elongation percent column",
      "source_detail": {
        "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
        "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
        "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
        "year": 2004,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "elongation",
      "label": "Elongation, cast-to-size Ti-48-2-2, 650 degC",
      "value": 5.1,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "alloy": "Ti-48Al-2Cr-2Nb cast to size",
        "temperature": "650 degC"
      },
      "method": "Average printed in the tensile property table of NASA TM 2004-212303",
      "status": "ground",
      "source": "nasa-2004",
      "where": "Table VII, Cast-to-size Ti-48-2-2 row, 650 degC, Elongation percent column",
      "source_detail": {
        "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
        "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
        "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
        "year": 2004,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "max_creep_temperature",
      "label": "Maximum temperature for creep, gamma class",
      "value": 900,
      "bound": "exact",
      "unit": "degC",
      "scope": "material",
      "conditions": {
        "basis": "gamma class column of Table I, class value"
      },
      "method": "Value printed in a comparison table (GE Aircraft Engines, 1992); not a measured creep limit for one alloy",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Max T - Creep row, Gamma column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "max_oxidation_temperature",
      "label": "Maximum temperature for oxidation, gamma class",
      "value": 815,
      "bound": "exact",
      "unit": "degC",
      "scope": "material",
      "conditions": {
        "basis": "gamma class column of Table I, class value; test atmosphere not printed"
      },
      "method": "Value printed in a comparison table (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Max T - Oxidation row, Gamma column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    },
    {
      "benchmark": "max_oxidation_temperature",
      "label": "Maximum temperature for oxidation, alpha-2 class",
      "value": 705,
      "bound": "exact",
      "unit": "degC",
      "scope": "material",
      "conditions": {
        "basis": "alpha-2 class column of Table I, class value; test atmosphere not printed"
      },
      "method": "Value printed in a comparison table (GE Aircraft Engines, 1992)",
      "status": "ground",
      "source": "gaa-1992",
      "where": "Table I, Max T - Oxidation row, Alpha-2 column",
      "source_detail": {
        "title": "Titanium Aluminides for Aerospace Applications",
        "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
        "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
        "year": 1992,
        "kind": "paper",
        "license": "TMS conference paper, cited not reproduced"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Air at high temperature (oxidation)",
      "headline": "Gamma TiAl is tabulated to resist oxidation up to 815 degC; alpha-2 Ti3Al to 705 degC.",
      "effect": "GE's comparison table gives the maximum oxidation temperature as 815 degC for the gamma class and 705 degC for the alpha-2 class. Its text calls gamma alloys excellent in oxidation resistance. The test atmosphere and exposure time are not printed.",
      "rating": "low",
      "conditions": {
        "basis": "class values from a 1992 review table; no Ti-48Al-2Cr-2Nb test is described"
      },
      "source": "gaa-1992",
      "where": "Table I, Max T - Oxidation row; Table II, Gamma column (Excellent oxidation resistance)"
    },
    {
      "environment": "Elevated temperature in general (oxidation and corrosion)",
      "headline": "Wikipedia cites oxidation and corrosion resistance at elevated temperatures for TiAl, above about 600 degC.",
      "effect": "The encyclopedia article says the alloys combine excellent mechanical properties with oxidation and corrosion resistance at elevated temperatures, over 600 degC. It is a general statement with no test conditions.",
      "rating": "low",
      "conditions": {
        "basis": "general statement in an encyclopedia article; no test conditions"
      },
      "source": "wiki-tial",
      "where": "Gamma-TiAl passage in the article"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem gives titanium (CID 23963) the GHS codes H228 (flammable solid), H250 (catches fire spontaneously if exposed to air) and H251 (self-heating; may catch fire), from ECHA C and L notifications. 606 of 808 company reports say it does not meet GHS hazard criteria.",
        "ghs": [
          "H228: Flammable solid",
          "H250: Catches fire spontaneously if exposed to air",
          "H251: Self-heating; may catch fire"
        ],
        "source": "pubchem-ti",
        "where": "Safety and Hazards, Hazards Identification, GHS Classification (CID 23963)"
      },
      {
        "text": "PubChem gives aluminum (CID 5359268) the GHS codes H250 (34.2 %), H261 (90.8 %) and H228 (60.6 %) from company reports. H261 means that it releases flammable gas in contact with water.",
        "ghs": [
          "H250: Catches fire spontaneously if exposed to air",
          "H261: In contact with water releases flammable gas",
          "H228: Flammable solid"
        ],
        "source": "pubchem-al",
        "where": "Safety and Hazards, GHS Classification (CID 5359268)"
      }
    ],
    "failure_risks": [
      {
        "mode": "Low room-temperature ductility",
        "trigger": "Loading at 23 degC, including impact",
        "consequence": "Cast-to-size Ti-48-2-2 elongates 1.70 % at 23 degC. NASA's program was set up because the limited ductility of gamma TiAl raised a concern about impact resistance.",
        "severity": "high",
        "source": "nasa-2004",
        "where": "Introduction (first paragraphs); Table VII, 23 degC row"
      },
      {
        "mode": "Cracking from impact",
        "trigger": "Impact tests at 260 degC in air under a 70 MPa tensile load, simulating LPT blade operating conditions",
        "consequence": "At higher impact energies, circumferential cracks grew through the thickness. At extreme energies a cone-shaped piece was removed (blowout), most often in the thin specimens.",
        "severity": "high",
        "source": "nasa-2004",
        "where": "Crack Morphology section (cast-to-size Ti-48-2-2)"
      },
      {
        "mode": "Casting porosity limits fatigue strength",
        "trigger": "High-cycle fatigue of unfretted and fretted specimens",
        "consequence": "The flat part of the stress-life curve is attributed to a high density of casting pores, which also masked the effect of fretting.",
        "severity": "moderate",
        "source": "nasa-2002",
        "where": "Results, stress-life curves of unfretted and fretted specimens"
      },
      {
        "mode": "Strength and ductility depend on aluminium content",
        "trigger": "Change of Al level from 48 at. % to 47.1 or 46.5 at. %",
        "consequence": "NASA reports that the strength and ductility of Ti-48Al-2Cr-2Nb vary with Al content, and that 47.1 at. % Al gave higher room-temperature yield strength at the same elongation.",
        "severity": "moderate",
        "source": "nasa-2004",
        "where": "Materials, chemistry paragraph"
      }
    ],
    "side_effects": [],
    "handling": [
      {
        "text": "Shipping of titanium powder: PubChem's DOT summary gives the shipping name for titanium powder wetted with not less than 25 percent water (a visible excess of water must be present), for mechanically produced particles under 53 microns.",
        "source": "pubchem-ti",
        "where": "Safety and Hazards, DOT Hazard Classification (CID 23963)"
      },
      {
        "text": "Test specimens were cast to size and the blades were cast overstock. The sources read give no heat-treatment window for the blade alloy.",
        "source": "nasa-2004",
        "where": "Introduction and Materials sections"
      }
    ],
    "mitigations": []
  },
  "uses": [
    {
      "application": "propulsion-and-tanks",
      "device": "Low-pressure turbine blades, GEnx engine",
      "example": "GE uses gamma TiAl for the low-pressure turbine blades on its GEnx engine, which powers the Boeing 787 and 747-8 and entered service in 2011.",
      "source": "wiki-tial",
      "where": "Applications section, GEnx paragraph"
    },
    {
      "application": "propulsion-and-tanks",
      "device": "Low-pressure turbine blades, LEAP engine (CFM International)",
      "example": "GE Aerospace lists the titanium aluminide low-pressure turbine blades among the LEAP engine's state-of-the-art technologies and materials.",
      "source": "ge-leap-avio",
      "where": "Article A LEAP for Avio Aero, sentence on the LEAP technologies and materials"
    },
    {
      "application": "propulsion-and-tanks",
      "device": "Engine-tested low-pressure turbine blades, Ti-48Al-2Cr-2Nb (GE, 1993)",
      "example": "GE Aircraft Engines manufactured low-pressure turbine blades from Ti-48Al-2Cr-2Nb and engine tested them in 1993. NASA then funded a team to optimise the design for commercial service.",
      "source": "nasa-2004",
      "where": "Introduction, first paragraph"
    }
  ],
  "supply": [
    {
      "subject": "Titanium sponge (feedstock for the titanium in TiAl)",
      "producers": [
        {
          "country": "China",
          "share_percent": 70.3,
          "year": 2025
        },
        {
          "country": "Japan",
          "share_percent": 14.3,
          "year": 2025
        },
        {
          "country": "Russia",
          "share_percent": 6.8,
          "year": 2025
        },
        {
          "country": "Kazakhstan",
          "share_percent": 4.3,
          "year": 2025
        },
        {
          "country": "Saudi Arabia",
          "share_percent": 3.2,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS 2025 List of Critical Minerals",
          "listed": true
        }
      ],
      "recycling": "USGS: titanium scrap imports were an estimated 32,000 t in 2025.",
      "substitutes": [
        "USGS: titanium competes with aluminum, composites, intermetallics, steel and superalloys in high-strength applications."
      ],
      "source": "usgs-ti-2026",
      "where": "World Sponge Metal Production table, 2025 column (world total 370,000 t, shares computed); Salient Statistics; Events, Trends, and Issues; Substitutes"
    },
    {
      "subject": "Aluminum (matrix element, about 48 at. %)",
      "producers": [
        {
          "country": "China",
          "share_percent": 60.8,
          "year": 2025
        },
        {
          "country": "India",
          "share_percent": 5.7,
          "year": 2025
        },
        {
          "country": "Russia",
          "share_percent": 5.3,
          "year": 2025
        },
        {
          "country": "Canada",
          "share_percent": 4.5,
          "year": 2025
        },
        {
          "country": "United Arab Emirates",
          "share_percent": 3.6,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS 2025 List of Critical Minerals",
          "listed": true
        }
      ],
      "recycling": "USGS: aluminum recovered from purchased scrap in the US was about 3.6 million tons in 2025.",
      "substitutes": [],
      "source": "usgs-al-2026",
      "where": "World Smelter Production and Capacity table, 2025e column (world total 74,000 thousand t, shares computed); Salient Statistics; Import Sources; Recycling"
    },
    {
      "subject": "Chromium (alloy addition, 2 at. %)",
      "producers": [
        {
          "country": "South Africa",
          "share_percent": 45.1,
          "year": 2025
        },
        {
          "country": "Turkey",
          "share_percent": 17.6,
          "year": 2025
        },
        {
          "country": "Kazakhstan",
          "share_percent": 13.7,
          "year": 2025
        },
        {
          "country": "India",
          "share_percent": 5.9,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS 2025 List of Critical Minerals",
          "listed": true
        }
      ],
      "substitutes": [],
      "source": "usgs-cr-2026",
      "where": "World Mine Production and Reserves table, 2025e column (chromium content, world total 51,000 thousand t, shares computed); Domestic Production and Use; Import Sources"
    },
    {
      "subject": "Niobium (alloy addition, 2 at. %)",
      "producers": [
        {
          "country": "Brazil",
          "share_percent": 93,
          "year": 2025
        },
        {
          "country": "Canada",
          "share_percent": 5,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS 2025 List of Critical Minerals",
          "listed": true
        }
      ],
      "substitutes": [],
      "source": "usgs-nb-2026",
      "where": "Domestic Production and Use text (Brazil about 93 % of global production; Canada 5 %); World Mine Production table, 2025e column (Brazil 104,000 t of 112,000 t world total)"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report (Draper et al.)",
      "type": "report",
      "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
      "year": 2004
    },
    {
      "title": "NASA/TM-2002-211718: Preliminary Study on Fatigue Strengths of Fretted Ti-48Al-2Cr-2Nb (Miyoshi et al.)",
      "type": "report",
      "url": "https://ntrs.nasa.gov/api/citations/20020081267/downloads/20020081267.pdf",
      "year": 2002
    },
    {
      "title": "Titanium Aluminides for Aerospace Applications (Chesnutt, Superalloys 1992, pp. 381-389)",
      "type": "paper",
      "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
      "year": 1992
    },
    {
      "title": "PubChem: Titanium (CID 23963), GHS classification and DOT summary",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/23963",
      "year": 2026
    },
    {
      "title": "PubChem: Aluminum (CID 5359268), GHS classification",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/5359268",
      "year": 2026
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Titanium",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf",
      "year": 2026
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Aluminum",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf",
      "year": 2026
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Chromium",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf",
      "year": 2026
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Niobium",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf",
      "year": 2026
    }
  ],
  "gaps": [
    "Designations (UNS, EN, AMS, ASTM) for gamma TiAl or Ti-48Al-2Cr-2Nb were not printed on any page read in this run, so identity.designations is left out.",
    "Density of the Ti-48Al-2Cr-2Nb alloy itself (about 3.9 g/cm3 is often quoted) was not found in a fetched source. The 3.8 and 4.04 g/cm3 values are family and class figures.",
    "Young's modulus for the blade alloy comes from one tabulated cast-to-size value (168 GPa) and one class value (176 GPa). No second source checked them.",
    "Fatigue, creep and tensile data above 650 degC for the blade alloy were not extracted. The 1992 creep limit is a class value, not a test.",
    "The room-temperature ductility range of the gamma class (1 to 3 %) in the 1992 table was not used, because the text layer of that PDF is garbled at that row.",
    "The oxidation test atmosphere, exposure time and scale data were not found. The OSTI abstract on Ti-48Al-2Nb-2Cr oxidation could not be reached in this run.",
    "Hydrogen embrittlement, galling and seawater or chloride behaviour: no fetched source.",
    "Space and vacuum data (outgassing, atomic oxygen erosion, thermal cycling in orbit): no source read.",
    "Blade manufacturing route (electron beam melting, casting suppliers) and the RTI supply agreement for LEAP blades appear only in search snippets, so they are not used.",
    "The LEAP claim rests on one sentence in a GE Aerospace article. The LEAP blade process is not confirmed.",
    "Alpha-2 Ti3Al figures are class averages from the 1992 GE table, not measurements of Ti3Al alone. Wikipedia gives only the D019 crystal structure.",
    "Crustal abundance of titanium, aluminum, chromium and niobium was not extracted from a fetched source.",
    "The EU critical raw materials list was not read. Only the USGS 2025 list was checked, from its web page.",
    "Two property names are not in spores/property-canon.yaml and are used as new names: max_creep_temperature and max_oxidation_temperature.",
    "Wikipedia states that some alloys keep oxidation resistance to 1,000 degC, but the page marks that claim as not specific enough to verify, so it is not used."
  ],
  "story": {
    "why": "Gamma TiAl is a light intermetallic for hot rotating parts. NASA gives its density as 3.8 g/cm3 for the family and calls its low density, together with good high-temperature properties, the reason it is a candidate for turbine machinery. GE built low-pressure turbine blades from Ti-48Al-2Cr-2Nb and engine tested them in 1993. Its main weakness is low ductility at room temperature, which made impact resistance the central question in NASA's program.",
    "uses": [
      {
        "where": "GEnx engine",
        "line": "GE uses gamma TiAl for the low-pressure turbine blades on its GEnx engine, which powers the Boeing 787 and 747-8 and entered service in 2011."
      },
      {
        "where": "LEAP engine",
        "line": "GE Aerospace lists the titanium aluminide low-pressure turbine blades among the LEAP engine's state-of-the-art technologies and materials. LEAP is built by CFM International."
      },
      {
        "where": "Engine test, 1993",
        "line": "GE Aircraft Engines engine-tested Ti-48Al-2Cr-2Nb low-pressure turbine blades in 1993. NASA then funded a team to optimise the design for commercial service."
      }
    ],
    "can_do": [
      {
        "label": "Density",
        "line": "NASA gives the density of the gamma TiAl family as 3.8 g/cm3. The GE review gives 4.04 g/cm3 for the gamma class, against 4.54 g/cm3 for titanium alloys and 8.3 g/cm3 for superalloys.",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Strength",
        "line": "Cast Ti-48-2-2 has a 0.2 % offset yield strength of 326 MPa at 23 degC and 284 MPa at 650 degC, with tensile strengths of 422 MPa and 474 MPa.",
        "benchmark": "yield_strength",
        "scope": "material"
      },
      {
        "label": "Stiffness",
        "line": "Cast Ti-48-2-2 has an elastic modulus of 168 GPa at 23 degC and 141 GPa at 650 degC. The gamma class is listed at 176 GPa, above the 110 GPa of titanium alloys in the same GE table.",
        "benchmark": "elastic_modulus",
        "scope": "material"
      },
      {
        "label": "Temperature",
        "line": "The GE table gives an oxidation limit of 815 degC for the gamma class, and a creep limit of 900 degC. The best GE gamma alloys held 550 MPa at 760 degC.",
        "benchmark": "max_oxidation_temperature",
        "scope": "material"
      }
    ],
    "compare": "In the GE comparison, gamma TiAl is lighter than titanium alloys and far lighter than superalloys, and it is stiffer than titanium alloys. It has much less room-temperature ductility than conventional titanium alloys and is more sensitive to impact. The alpha-2 class is denser at 4.84 g/cm3 and has a lower oxidation limit of 705 degC.",
    "compare_rows": [
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Elastic modulus",
        "benchmark": "elastic_modulus",
        "scope": "material"
      },
      {
        "label": "Yield strength",
        "benchmark": "yield_strength",
        "scope": "material"
      }
    ],
    "handling": [
      "Powder and swarf: PubChem gives H228, H250 and H251 for titanium. Keep powder dry, away from air and heat, and away from ignition sources.",
      "Shipping: the DOT entry for titanium powder requires it to be wetted with at least 25 percent water.",
      "Blades and specimens: the NASA work used cast-to-size and cast overstock parts, and the sources read give no heat-treatment window."
    ],
    "good_for": [
      "Lightweight hot rotating parts. The family density is 3.8 g/cm3, and cast Ti-48-2-2 holds 474 MPa tensile strength at 650 degC.",
      "Stiffness and oxidation. The gamma class is listed at 176 GPa and an oxidation limit of 815 degC."
    ],
    "watch_out": [
      "Room-temperature ductility: cast Ti-48-2-2 elongates 1.70 % at 23 degC.",
      "Impact damage can crack thin sections and, at high energy, remove material in a blowout.",
      "Properties depend on Al content and microstructure. NASA found that 47.1 at. % Al gave higher room-temperature yield strength than 48 at. %.",
      "The alpha-2 class is denser at 4.84 g/cm3 and has a lower oxidation limit of 705 degC."
    ],
    "verdict": "Gamma TiAl is a stiff, light, heat-tolerant intermetallic that GE has used in engine turbines, most recently in the GEnx and LEAP. Its low ductility and sensitivity to impact are the main limits. The sources read here give no space, seawater or hydrogen data.",
    "recipe": {
      "line": "Gamma TiAl is an intermetallic compound of titanium and aluminium. The turbine-blade alloy Ti-48Al-2Cr-2Nb (at. %) is cast, and NASA describes its microstructure as duplex, with gamma grains and gamma plus alpha-2 lamellar colonies. Alpha-2 Ti3Al is a separate class based on a hexagonal D019 structure.",
      "parts": [
        {
          "name": "Titanium",
          "symbol": "Ti",
          "role": "Base metal. Titanium makes up the rest of the alloy after the other elements.",
          "share_note": "balance (the rest)",
          "source": "nasa-2004",
          "where": "Introduction, Ti-48Al-2Cr-2Nb (at.%); balance is implied by the nominal composition"
        },
        {
          "name": "Aluminium",
          "symbol": "Al",
          "role": "Main alloying element. The cast-to-size samples measured 47.5 at. % Al, and a slightly lower Al level gave higher room-temperature yield strength in NASA's test.",
          "share_percent": 48,
          "share_note": "at. %, nominal",
          "source": "nasa-2004",
          "where": "Introduction, Ti-48Al-2Cr-2Nb (at.%); Materials, chemistry paragraph"
        },
        {
          "name": "Chromium",
          "symbol": "Cr",
          "role": "Alloying addition. In the cited oxidation comparison, Cr and Nb additions raised oxidation resistance over binary TiAl.",
          "share_percent": 2,
          "share_note": "at. %, nominal",
          "source": "nasa-2004",
          "where": "Introduction, Ti-48Al-2Cr-2Nb (at.%)"
        },
        {
          "name": "Niobium",
          "symbol": "Nb",
          "role": "Alloying addition for strength and oxidation resistance.",
          "share_percent": 2,
          "share_note": "at. %, nominal",
          "source": "nasa-2004",
          "where": "Introduction, Ti-48Al-2Cr-2Nb (at.%)"
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "The solid alloy has no hazard class in the sources read. The powder is the concern: PubChem gives titanium and aluminum powders flammable-solid and related classes.",
        "points": [
          {
            "label": "Solid alloy",
            "line": "PubChem reports titanium as not meeting GHS hazard criteria in 606 of 808 company reports. The NASA and GE sources give no hazard class for the alloy."
          },
          {
            "label": "Powder and swarf",
            "line": "Titanium powder carries H228, H250 and H251 in PubChem. Aluminum powder carries H250, H261 and H228. Treat both as fire hazards and keep them away from air and water."
          }
        ],
        "level": 0,
        "verdict": "Solid alloy not classified; powder and swarf are flammable"
      },
      {
        "title": "Shipping",
        "lead": "Titanium powder is a regulated shipping item in the United States.",
        "points": [
          {
            "label": "Wetted powder",
            "line": "The DOT summary lists titanium powder wetted with not less than 25 percent water, with a visible excess of water present, for mechanically produced particles under 53 microns."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-26",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 22,
    "unreachable": 1,
    "caveats": 4,
    "note": "Written 2026-10-26 by an assistant from pages read in this run. Gamma TiAl composition, Ti-48-2-2 tensile and modulus values, and class densities and oxidation limits come from NASA and GE sources. Supply shares are computed from USGS tonnage. The OSTI oxidation abstract was unreachable."
  },
  "sources": {
    "nasa-2004": {
      "title": "NASA/TM-2004-212303: Durability Assessment of Gamma TiAl, Final Report",
      "id": "NASA TM 2004-212303, Draper, Lerch, Pereira, Miyoshi and Arya",
      "url": "https://ntrs.nasa.gov/api/citations/20040028027/downloads/20040028027.pdf",
      "year": 2004,
      "kind": "report",
      "license": "public domain (NASA)"
    },
    "nasa-2002": {
      "title": "NASA/TM-2002-211718: Preliminary Study on Fatigue Strengths of Fretted Ti-48Al-2Cr-2Nb",
      "id": "NASA TM 2002-211718, Miyoshi, Lerch and Draper",
      "url": "https://ntrs.nasa.gov/api/citations/20020081267/downloads/20020081267.pdf",
      "year": 2002,
      "kind": "report",
      "license": "public domain (NASA)"
    },
    "gaa-1992": {
      "title": "Titanium Aluminides for Aerospace Applications",
      "id": "Chesnutt, J.C., Superalloys 1992, TMS, pp. 381-389",
      "url": "https://www.tms.org/Superalloys/10.7449/1992/Superalloys_1992_381_389.pdf",
      "year": 1992,
      "kind": "paper",
      "license": "TMS conference paper, cited not reproduced"
    },
    "wiki-tial": {
      "title": "Titanium aluminide (Wikipedia)",
      "id": "Wikipedia, Titanium aluminide",
      "url": "https://en.wikipedia.org/wiki/Titanium_aluminide",
      "year": 2026,
      "kind": "web",
      "license": "CC BY-SA 4.0"
    },
    "ge-leap-avio": {
      "title": "A LEAP for Avio Aero (GE Aerospace article)",
      "id": "GE Aerospace news article",
      "url": "https://www.geaerospace.com/news/articles/product/leap-avio-aero",
      "year": 2026,
      "kind": "web",
      "license": "manufacturer web page, cited not reproduced"
    },
    "pubchem-ti": {
      "title": "PubChem: Titanium (CID 23963), GHS classification and DOT summary",
      "id": "PubChem CID 23963",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/23963",
      "year": 2026,
      "kind": "database",
      "license": "PubChem, public"
    },
    "pubchem-al": {
      "title": "PubChem: Aluminum (CID 5359268), GHS classification",
      "id": "PubChem CID 5359268",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/5359268",
      "year": 2026,
      "kind": "database",
      "license": "PubChem, public"
    },
    "usgs-ti-2026": {
      "title": "Mineral Commodity Summaries 2026: Titanium (USGS, February 2026)",
      "id": "USGS MCS 2026, Titanium",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf",
      "year": 2026,
      "kind": "report",
      "license": "US Government work, public domain"
    },
    "usgs-al-2026": {
      "title": "Mineral Commodity Summaries 2026: Aluminum (USGS, February 2026)",
      "id": "USGS MCS 2026, Aluminum",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf",
      "year": 2026,
      "kind": "report",
      "license": "US Government work, public domain"
    },
    "usgs-cr-2026": {
      "title": "Mineral Commodity Summaries 2026: Chromium (USGS, February 2026)",
      "id": "USGS MCS 2026, Chromium",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf",
      "year": 2026,
      "kind": "report",
      "license": "US Government work, public domain"
    },
    "usgs-nb-2026": {
      "title": "Mineral Commodity Summaries 2026: Niobium (USGS, February 2026)",
      "id": "USGS MCS 2026, Niobium",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf",
      "year": 2026,
      "kind": "report",
      "license": "US Government work, public domain"
    },
    "usgs-crit2025": {
      "title": "About the 2025 List of Critical Minerals (USGS)",
      "id": "Final 2025 List of Critical Minerals, November 2025",
      "url": "https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals",
      "year": 2025,
      "kind": "web",
      "license": "public domain (USGS)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/titanium-aluminide/"
}