High temperature resistant TiAl alloy, production method therefor and component made therefrom
Described is a TiAl alloy which, besides titanium, comprises 42 to 48 at. % aluminum, 3 to 5 at. % niobium, 0.05 to 1 at. % molybdenum, 0.2 to 2.2 at. % silicon, 0.2 to 0.4 at. % carbon, 0.05 to 0.2 at. % boron, and optionally tungsten, zirconium and hafnium, as well as unavoidable impurities, and at room temperature has a microstructure which comprises globular colonies of lamellae of α 2 -Ti 3 Al and γ-TiAl, as well as silicide precipitates, and essentially no β phase. A method for producing a component made of this alloy is also described.
1. A TiAl alloy, wherein the alloy comprises
from 43.5 to 45 at. % aluminum,
from 3.5 to 4.5 at. % niobium,
from 0.1 to 0.5 at. % molybdenum,
from 0.4 to 1 at. % tungsten,
from 0.25 to 0.35 at. % silicon,
from 0.25 to 0.35 at. % carbon,
from 0.05 to 0.15 at. % boron,
and unavoidable impurities, titanium being provided in a quantity such that the sum of proportions of chemical elements amounts to 100 at. %, and the TiAl alloy having at room temperature a microstructure which comprises globular colonies of lamellae of α 2 -Ti 3 Al and γ-TiAl, as well as silicide precipitates, and essentially no β phase.
2. A component made of the TiAl alloy of claim 1 .
3. The component of claim 2 , wherein the TiAl alloy comprises less than 5 vol. % of β phase at working temperatures of up to 900° C.
4. The component of claim 2 , wherein the globular colonies of lamellae of α 2 -Ti 3 Al and γ-TiAl form at least 95 vol. % of the TiAl alloy.
5. The component of claim 2 , wherein the TiAl alloy contains up to 5 wt. % of silicides, carbides and/or borides, an average or maximum grain size of the silicides, carbides and/or borides being less than or equal to 5 μm.
6. A TiAl alloy, wherein the alloy comprises
from 43.5 to 45 at. % aluminum,
from 3.5 to 4.5 at. % niobium,
from 0.85 to 0.95 at. % molybdenum,
from 0.1 to 3 at. % zirconium,
from 0.25 to 2.2 at. % silicon,
from 0.25 to 0.35 at. % carbon,
from 0.05 to 0.15 at. % boron,
and unavoidable impurities, titanium being provided in a quantity such that the sum of proportions of chemical elements amounts to 100 at. %, and the TiAl alloy having at room temperature a microstructure which comprises globular colonies of lamellae of α 2 -Ti 3 Al and γ-TiAl, as well as silicide precipitates, and essentially no β phase.
7. A component made of the TiAl alloy of claim 6 .
8. The component of claim 7 , wherein the TiAl alloy comprises less than 5 vol. % of β phase at working temperatures of up to 900° C.
9. The component of claim 7 , wherein the globular colonies of lamellae of α 2 -Ti 3 Al and γ-TiAl form at least 95 vol. % of the TiAl alloy.
10. A TiAl alloy, wherein the alloy comprises
from 46 to 48 at. % aluminum,
from 3.5 to 5 at. % niobium,
from 0.1 to 0.5 at. % molybdenum,
from 0.4 to 1.8 at. % tungsten,
from 0.1 to 3 at. % zirconium,
from 0.35 to 2.2 at. % silicon,
from 0.25 to 0.35 at. % carbon,
from 0.05 to 0.15 at. % boron,
and unavoidable impurities, titanium being provided in a quantity such that the sum of proportions of chemical elements amounts to 100 at. %, and the TiAl alloy having at room temperature a microstructure which comprises globular colonies of lamellae of α 2 -Ti 3 Al and γ-TiAl, as well as silicide precipitates, and essentially no β phase.
11. A component made of the TiAl alloy of claim 10 .
12. The component of claim 11 , wherein the TiAl alloy comprises less than 5 vol. % of β phase at working temperatures of up to 900° C.
13. The component of claim 11 , wherein the globular colonies of lamellae of α 2 -Ti 3 Al and γ-TiAl form at least 95 vol. % of the TiAl alloy.
14. A method for producing a component made of a TiAl alloy, wherein the method comprises
melting a TiAl alloy which comprises
titanium,
from 42 to 48 at. % aluminum,
from 3 to 5 at. % niobium,
from 0.05 to 1 at. % molybdenum,
from 0.2 to 2.2 at. % silicon,
from 0.2 to 0.4 at. % carbon,
from 0.05 to 0.2 at. % boron,
0 to 2.0 at. % tungsten,
0 to 3.5 at. % zirconium,
0 to 0.3 at. % hafnium,
and unavoidable impurities, titanium being provided in a quantity such that the sum of proportions of chemical elements amounts to 100 at. %, with the proviso that the alloy comprises
(i) at least 46 at. % aluminum; and/or
(ii) not more than 0.5 at. % molybdenum; and/or
(iii) at least one of tungsten, zirconium, and hafnium;
casting the melted TiAl alloy to form a semifinished product or atomizing the TiAl alloy to form a powder,
precipitation-stabilizing the semifinished product, or a preliminary product produced from the semifinished product or the powder, by cooling the semifinished product or the preliminary product from a silicide starting temperature so that silicides are precipitated,
heat-treating the precipitation-stabilized semifinished product or preliminary product in the α phase temperature range, in which silicide precipitates are present, for from 0.5 to 2 hours and cooling, so that globular colonies of lamellae of α 2 -Ti 3 Al and γ-TiAl are formed.
15. The method of claim 14 , wherein precipitation stabilization is carried out directly during solidification from a melt or during cooling after compaction or shaping, and/or the silicide starting temperature lies above or below a silicide dissolution temperature.
16. The method of claim 14 , wherein the α phase temperature range lies below a silicide dissolution temperature and above a gamma solvus temperature.
17. The method of claim 14 , wherein the α phase temperature range, a silicide dissolution temperature and/or a gamma solvus temperature of the TiAl alloy is determined by simulation calculations and/or by test melts and metallographic examinations.
18. The method of claim 14 , wherein the TiAl alloy comprises at least one of tungsten, zirconium, and hafnium.
19. The method of claim 14 , wherein the TiAl alloy is selected in such a way that the TiAl alloy exhibits peritectic solidification with α-Ti phase formation or solidification with β phase formation.
20. The method of claim 14 , wherein the heat-treated semifinished product or preliminary product is subjected to a second heat treatment at a temperature below a gamma solvus temperature for from 2 hours to 24 hours.