DE102017109156A1 - High-temperature resistant material and its production - Google Patents

Abstract

The invention relates to a structure of intermetallic B2 and C14 phases, wherein the primary precipitated C14 phase forms essentially non-interconnected regions (islands), the islands of the C14 phase are enclosed by the B2 phase, the total volume of the C14 molecules Phase in the structure over that of the B2 phase predominates. Furthermore, the invention relates to a method for producing the microstructure and a use.

Description

The invention relates to a highly heat-resistant material based on intermetallic phases and a method for adjusting its microstructure.

Thermally and mechanically highly resilient workpieces are required, inter alia, in turbomachines, in gas turbines, in internal combustion engines and in aircraft engines. The need for improved in terms of mechanical and thermal stress materials is still there.

A common production step in the production of the corresponding workpieces is the thermomechanical treatment to improve the properties. For this purpose, only tools (dies) are suitable, which in turn at the high temperatures at which they are used have a higher strength than the workpiece to be machined.

Intermetallic phases give rise to the assumption that they are suitable for improving the mechanical and thermal resistance of materials, since intermetallic phases have a higher mechanical and thermal resistance compared to metallic materials.

Various intermetallic phases, different types of structures are known. The Laves phases named after the mineralogist Fritz Laves form one of the largest groups of intermetallic compounds of defined composition of hexagonal C14 or C36 structure or cubic C15 structure.

The content of Publication Gerhard Sauthoff "Intermetallics" ISBN: 978-3-527-61540-7 is explicitly included.

The DE 600 24 189 T2 describes a steel whose creep resistance is improved by precipitations of an intermetallic inter alia Laves phase.

The DE2521563A1 (Sprenger) describes a molybdenum-containing metallic nickel-based alloy which is reinforced by precipitates of intermetallic phases. Directional solidification enforces a lamellar texture of the intermetallic phase.

The EP 0760 869 B1 (Applicant: Siemens, HC Starck) describes an intermetallic nickel-aluminum base alloy in which precipitates of a Laves phase occur by adding tantalum and chromium to the grain boundaries of the B2 primary precipitates.

The DE 10 2013 214 767 A1 (Applicant: MTU Aero Engines AG) also describes a nickel-aluminum alloy having an increased content of nickel in which precipitates of hexagonal Laves phase having C14 structure occur by adding niobium or tantalum to the grain boundaries of B2 primary precipitates.

The invention has for its object to provide materials with improved thermo-mechanical properties and a method for adjusting the necessary structure. Furthermore, it is the object of the invention to provide a material for a die for producing highly heat-resistant workpieces.

It has now been found that the mechanical and thermal load-bearing capacity of workpieces consisting of two intermetallic phases of the structure B2 and C14, in the absence of further metallic or intermetallic phases, can be improved by means of a special structure. The microstructures according to the invention are characterized by primary excretions of the C14 phase and a resteutectic composition in which the volume fraction of the B2 phase forms the matrix of the microstructure and thus encloses islands of the C14 phase.

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings, which are intended to illustrate the invention and are not to be considered as limiting:

Show it:

: SEM image of a microstructure according to the invention

: Binary phase diagram, state diagram of the system TaNiAl with a ratio of Ni to Al (Ni / Al) of 0.66

: Qualitative representation of the structure, depending on the tantalum content of the system TaNiAl (B2 white, C14 gray)

: Binary phase diagram, state diagram of the system TaNiAl with a ratio of Ni to Al (Ni / Al) of 1.1

: Binary phase diagram, state diagram of the system TaNiAl with a ratio of Ni to Al (Ni / Al) of 0.85

: SEM image of a structure not according to the invention from example 2 (Ta _6.3 Ni _42.8 Al _50.9 )

: Binary phase diagram, state diagram of the system TaNiAl with a ratio of Ni to Al (Ni / Al) of 1.2

: SEM image of a structure not according to the invention from example 3 (Ta _8,5 Ni _49,5 Al ₄₂ )

: SEM image of a structure not according to the invention from Example 4 (Ta _24.3 Ni _41.3 Al _34.4 )

: Binary phase diagram, state diagram of the system NbNiAl with a ratio of Ni to Al (Ni / Al) of 0.66

: Binary phase diagram, state diagram of the system NbNiAl with a ratio of Ni to Al (Ni / Al) of 0.75

: SEM image of the structure according to the invention Nb _24.3 Ni ₃₀ Al _44.7 Example 5

: SEM image of the noninventive structure Nb _13.4 Ni _45.9 Al _40.7 Example 6

: Binary phase diagram, state diagram of the system NbNiAl with a ratio of Ni to Al (Ni / Al) of 1.12

: SEM image of the structure according to the invention Ta _22.5 Ni _35.9 Al _41.6

shows a scanning electron microscope image of a microstructure according to the invention. The bright islands are formed by the C14 phase, the dark areas are the surrounding B2 matrix.

It was found that the mechanical and thermal loading of workpieces of B2 and C14 intermetallic phases can be improved if the system is chosen to first excrete the extremely hard C14 phase and if it is ensured that the volume fraction of the B2 phase predominates in the eutectic composition and forms an enclosing matrix around the "island-like" distributed C14 phase.

Furthermore, it was recognized that the total volume of the C14 phase in the microstructure must predominate over that of the B2 phase.

Structures according to the invention are formed when the composition of a melt is selected such that first primary precipitates of the C14 phase initially form in the course of solidification. The residual melt develops, until complete solidification, towards the eutectic composition. This connection is in to recognize.

Only when solidification of this residual melt also forms a B2 phase. ( , the residual melt solidifies to B2 and C14). With predominant volume fraction (can be calculated from the associated state diagram) of the B2 phase in the eutectic composition (residual melt) this forms a matrix around the C14 precipitates. The B2 phase encases the C14 particles as a matrix and is connected throughout the system while the C14 phase forms "islands".

A qualitative representation of the structure according to the invention and the non-inventive structure is in shown. If, in the case of a composition in the system, TaNiAl ( ) selected a starting composition to the left of the eutectic (0-8.8 at% Ta), initially formed on solidification B2 Erstausscheidungen. If, on the other hand, a starting composition to the right of the eutectic (8.8-33 at% Ta) is chosen, first C14 initial precipitates form on solidification. Independently of this, the residual melt, which encloses the initial precipitates as a liquid phase, always reaches the eutectic composition until complete solidification. From the melt is as long as B2 or C14 excreted until the residual melt is present in eutectic composition and also solidifies.

• i. Auswahl eines der sechs Grundsysteme bestehend aus drei verschiedenen Metallen, A, B und C. Wobei A Aluminium (Al), B Eisen (Fe) oder Nickel (Ni) und C Tantal (Ta), Niob (Nb) oder Titan (Ti) ist., i.e. NbNiAl, TaNiAl, TiNiAl, NbFeAl, TaFeAl und TiFeAl. Wobei die Metalle A und B (AlNi und AlFe) eine B2-Phase und die Metalle A und B und C eine C14-Phase bilden.
• ii. Spezifizierung der in Schritt i getroffenen Auswahl anhand von Gleichung 1 (Gl.1) und Gleichung 2 (Gl.2) auf solche Systeme, welche in eutektischer Zusammensetzung ein volumetrisches Überwiegen der B2-Phase gegenüber der C14-Phase aufweisen
  
  V_B2 = 100% – V_C14 Gl. 2 mit:

  V_mC14

  = Molvolumen [m³/mol] der C14-Phase

  V_mB2

  = Molvolumen [m³/mol] der B2-Phase

  V_C14

  = Volumenanteil [%] der C14-Phase

  V_B2

  = Volumenanteil [%] der B2-Phase

  X_c

  = Stoffmengenanteil der Komponente C (für X_C ist der Stoffmengenanteil der Komponente C in eutektischer Zusammensetzung einzusetzen V_B2 -> V_B2-eut)

• iii. Sicherstellen das der der Volumenanteil der C14-Phase in folgenden Grenzen liegt: obere Grenze: V_C14max = 90 vol.% des Gesamtvolumens untere Grenze: V_C14min = V_B2eut + 1/3·(V_C14max – V_B2eut)
  

The novel microstructures according to the invention are obtained when a method comprising the following steps is used:

• i. Selection of one of the six basic systems consisting of three different metals, A, B and C. Where A is aluminum (Al), B is iron (Fe) or nickel (Ni) and C is tantalum (Ta), niobium (Nb) or titanium (Ti) NbNiAl, TaNiAl, TiNiAl, NbFeAl, TaFeAl and TiFeAl. Where metals A and B (AlNi and AlFe) form a B2 phase and metals A and B and C form a C14 phase.
• ii. Specification of the selection made in step i using Equation 1 (Equ. 1) and Equation 2 (Equ. 2) for those systems which, in eutectic composition, have a volumetric preponderance of the B2 phase relative to the C14 phase
  
  V _B2 = 100% - V _C14 Eq. 2 With:

  V _mC14

  = Molar volume [m ³ / mol] of the C14 phase

  V _mB2

  = Molar volume [m ³ / mol] of the B2 phase

  V _C14

  = Volume fraction [%] of the C14 phase

  V _B2

  = Volume fraction [%] of the B2 phase

  X _c

  = Molar fraction of component C (for X _C , the molar fraction of component C in eutectic composition is to be used V _B2 -> V _B2-eut )

• iii. Ensure that the volume fraction of the C14 phase is within the following limits: Upper limit: V _C14max = 90 vol.% _Of the total volume lower limit: V _C14min = V _B2eut + _1/3 · (V _C14max - V _B2ew )
  

By _using V _C14max in Eq. 3, the maximum _mole fraction of component C, X _{maxC is} calculated by _substituting V _C14min in Eq. 4, the minimum _mole fraction of component C, X _{minC is} calculated. The total composition is chosen such that for the mole fraction of component C (X _C ): X _minC <X _C <X _maxC

The production of the melt takes place after the expert in general and in particular, for example from the EP 0 760 869 B1 and Lothar Machon "Investigation of the Deformation Behavior of High-Fusing Hexagonal Laves Phases". Suitable are both inductive Schweehmmelzverfahren, arc melting and electron beam melting and crucible melting with subsequent casting in a heated mold. Powder metallurgical processes, primarily sintering and hot isostatic pressing, are suitable for shaping. The metals of positions A and B of the structure according to the invention can be substituted up to 3 at.% By the element chromium. The metals of position C can be substituted up to 3 at.% By the elements hafnium and / or zirconium.

The microstructure according to the invention produced by the process according to the invention is 2-phase systems consisting of a comparatively ductile B2 and a very hard / solid C14 phase. The microstructure is characterized by the fact that precipitations (both primary and residual precipitates) of the C14 phase are embedded in a matrix of B2 phase. Extremely high strengths are achieved when the (very solid) C14 phase predominates in the volumetric composition of the microstructure, and the (less solid) matrix becomes so "thin" that external stresses in it (the matrix) are almost exclusively at hydrostatic pressure result. The microstructures according to the invention are suitable as materials which require high strength and high heat resistance. Such materials are used in particular for the production of high temperature loaded components of gas turbines, such as e.g. Gas turbine blades and in gas turbine aircraft engines needed.

The microstructures according to the invention are particularly suitable as high-temperature-resistant materials for dies for the production of articles which require high strength and high heat resistance. In the following, the method according to the invention is demonstrated as the generality not restricting by way of example. We are looking for a material for a forging die for forming high-temperature components. During forging, the temperature of the die reaches about 1300 ° C. The two basic systems NbNiAl and TaNiAl are treated by the six possible basic systems NbNiAl, TaNiAl, TiNiAl, NbFeAl, TaFeAl and TiFeAl, which form a B2 phase (AlB) and a C14 phase (AlBC).

System TaNiAl from step i:

• The molar volume of the C14 phase of the chosen basic system is: V _mC14 = 25.3 cm ³ / mol
• The molar volume of the corresponding B2 phase: V _mB2 = 14.7 cm ³ / mol

• • Anwendung von Schritt ii für Ni/Al = 0,66: Hier ist der Stoffmengenanteil von Tantal in eutektischer Zusammensetzung Xc = 8,8 at%. Dieses ist in , dem Zustandsschaubild des Systems TaNiAl mit einem Verhältnis von Ni zu Al (Ni/Al) von 0,66 zu erkennen. Es wird in Gl. 1 eingesetzt.
  
  Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 38,2% = 61,8% ergibt V_B2eut = 61,8 vol% und überwiegt somit in der Restschmelze.
• • Anwendung von Schritt ii für Ni/Al = 1,1: Hier ist der Stoffmengenanteil von Tantal in eutektischer Zusammensetzung Xc = 11 at%. Dieses ist entnehmbar aus dem Zustandsschaubild des Systems TaNiAl mit einem Verhältnis von Ni zu Al (Ni/Al) von 1,1 ( )
• • Es wird dieser Wert in Gl. 1 eingesetzt.
  
  Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 45,9% = 54,1% ergibt V_B2eut = 54,1 vol% und überwiegt somit in der Restschmelze.
• • Der maximale Tantalgehalt wird nun nach Schritt iii berechnet. Gl. 3 liefert:
  
• • Der minimale Tantalgehalt ergibt sich anhand der eutektischen Zusammensetzung: 1. Anwendung von Schritt iii für die untere Grenze des Stoffmengenverhältnisses von Nickel zu Aluminium (Ni/Al = 0,66): V_B2eut = 61,8 vol% wird in die Formel zur Berechnung der unteren Grenze des C14 Volumenanteils eingesetzt: V_C14min = V_B2eut + 1/3·(V_C14max – V_B2eut) = 61,8 vol% + 1/3·(90 vol% – 61,8 vol%) = 71,2 vol%. Die so erhaltene untere Grenze des Volumenanteils wird in Gl. 4 eingesetzt:
  
  ergibt einen minimalen Stoffmengenanteil von Tantal von 22,8 at% 2. Anwendung von Schritt iii für die obere Grenze des Stoffmengenverhältnisses von Nickel zu Aluminium (Ni/Al = 1,1): V_B2eut = 54,5 vol% wird in die Formel zur Berechnung der unteren Grenze des C14 Volumenanteils eingesetzt: V_C14min = V_B2eut + 1/3·(V_C14max – V_B2eut) = 54,5 vol% + 1/3·(90 vol% – 54,5 vol%) = 66,3 vol%. Die so erhaltene untere Grenze des Volumenanteils wird in Gl. 4 eingesetzt:
  
  ergibt einen minimalen Stoffmengenanteil von Tantal von 21 at%

Structures according to the invention are set within the following stoichiometric limits:
The molar ratio of nickel to aluminum (Ni / Al) ranges from 0.66 to 1.1. The mole fraction of tantalum is between 21 at% and 22.8 at% (depending on Ni / Al) and 29.6 at%

• • Application of step ii for Ni / Al = 0.66: Here, the mole fraction of tantalum in eutectic composition is Xc = 8.8 at%. This is in , the state diagram of the system TaNiAl with a ratio of Ni to Al (Ni / Al) of 0.66 to recognize. It is reflected in Eq. 1 used.
  
  The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 38.2% = 61.8% V _B2eut = 61.8 vol% and thus predominates in the residual melt.
• • Application of step ii for Ni / Al = 1,1: Here, the mole fraction of tantalum in eutectic composition is Xc = 11 at%. This can be taken from the state diagram of the system TaNiAl with a ratio of Ni to Al (Ni / Al) of 1.1 ( )
• • This value in Eq. 1 used.
  
  The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 45.9% = 54.1% V _B2euter = 54.1 vol% and thus prevails in the residual melt.
• • The maximum tantalum content is now calculated after step iii. Eq. 3 supplies:
  
• • The minimum tantalum content is given by the eutectic composition: 1. Application of step iii for the lower limit of the molar ratio of nickel to aluminum (Ni / Al = 0.66): V _B2eut = 61.8 vol% is added to the formula Calculation of the lower limit of the C14 volume fraction used: V _C14min = V _B2eut + _1/3 · (V _C14max - V _B2eut ) = 61.8 vol% + _1/3 · (90 vol% - 61.8 vol%) = 71.2 vol%. The lower limit of the volume fraction thus obtained is given in Eq. 4 used:
  
  gives a minimum molar fraction of tantalum of 22.8 at%. 2. Application of step iii for the upper limit of molar ratio of nickel to aluminum (Ni / Al = 1.1): V _B2eut = 54.5 vol% is expressed in the formula used to calculate the lower limit of the C14 volume fraction: V _C14min = V _B2eut + _1/3 · (V _C14max - V _B2eut ) = 54.5 vol% + _1/3 · (90 vol% - 54.5 vol%) = 66.3 vol%. The lower limit of the volume fraction thus obtained is given in Eq. 4 used:
  
  gives a minimum mole fraction of tantalum of 21 at%

Four compositions in the system TaNiAl are considered below by way of example. Compositions with a higher Ni content than Al (Examples 3 and 4) do not lead to the structure according to the invention. Also, the hypoeutectic Example 2 (V _C14 <V _C14min ) prepared with a higher Al content than Ni content does not lead to the microstructure _according to the invention. The hypereutectic Example 1 (V _C14 > V _C14min ) prepared with a higher Al content than Ni content leads to the microstructure _according to the invention.

The example structures were produced by means of multiple remelting from the pure components in an arc melt. The micrographs are SEM images in the secondary electron image method. Compositions were determined in the REM by EDX.

Example 1 Ta _22.5 Ni _35.9 Al _41.6 (Fig. 1 and Fig. 15) Example according to the invention

Step i

• Selection of the basic system: -> A = Al, B = Ni, C = Ta V _mC14 = 25.3 cm ³ / mol V _mB2 = 14.7 cm ³ / mol

Step ii

Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 41,75% = 58,25% ergibt V_B2eut = 58,25 vol% und überwiegt somit in der Restschmelze. The mole fraction of tantalum in eutectic composition is in the composition mentioned above (Ni / Al = 0.85) at 9.8 at% (state diagram in ). Insertion in Eq. 1:

The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 41.75% = 58.25% V _B2eut = 58.25 vol% and thus predominates in the residual melt.

Step iii

V_B2eut = 58,25 vol% wird in die Formel zur Berechnung der unteren Grenze des C14 Volumenanteils eingesetzt: V_C14min = 58,25 vol% + 1/3·(90 vol% – 58,25 vol%) = 68,8 vol%. Die so erhaltene untere Grenze des Volumenanteils wird in Gl. 4 eingesetzt:

Der Stoffmengenanteil von Tantal (X_C) mit 22,5 at% liegt somit innerhalb der Zulässigen Grenzen: 21,9 at% < X_C < 29,6 at% The upper limit for the mole fraction of tantalum with Eq. 3 calculated:

V _B2eut = 58.25 vol% is used in the formula for calculating the lower limit of the C14 volume fraction: V _C14min = 58.25 vol% + _1/3 x (90 vol% - 58.25 vol%) = 68.8 vol%. The lower limit of the volume fraction thus obtained is given in Eq. 4 used:

The mole fraction of tantalum (X _C ) at 22.5 at% is therefore within the permissible limits: 21.9 at% <X _C <29.6 at%

The test according to method step iii shows that the conditions for forming a microstructure according to the invention are fulfilled here. Consequently, initial precipitates of the C14 phase (bright areas) are formed, surrounded by a matrix of the B2 phase (dark areas). Structure according to the invention.

Example 2 Ta _6.3 Ni _42.8 Al _50.9 (Fig. 6)

Step i

• Selection of the basic system: -> A = Al, B = Ni, C = Ta V _mC14 = 25.3 cm ³ / mol V _mB2 = 14.7 cm ³ / mol

Step ii

Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 41,4% = 58,6% ergibt V_B2eut = 58,6 vol% und überwiegt somit in der Restschmelze. The mole fraction of tantalum in eutectic composition is in the above composition (Ni / Al = 0.84) at 9.7 at% ( ). Insertion in Eq. 1:

The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 41.4% = 58.6% V _B2eut = 58.6 vol% and thus predominates in the residual melt.

Step iii

V_B2eut = 58,6 vol% wird in die Formel zur Berechnung der unteren Grenze des C14 Volumenanteils eingesetzt: V_C14min = 58,6 vol% + 1/3·(90 vol% – 58,25 vol%) = 69 vol%. Die so erhaltene untere Grenze des Volumenanteils wird in Gl. 4 eingesetzt:

Der Stoffmengenanteil von Tantal (X_C) mit 6,3 at% liegt somit außerhalb der Zulässigen Grenzen: 22 at% < X_C < 29,6 at% The upper limit for the mole fraction of tantalum with Eq. 3 calculated:

V _B2eut = 58.6 vol% is used in the formula for calculating the lower limit of the C14 volume fraction: V _C14min = 58.6 vol% + _1/3 x (90 vol% - 58.25 vol%) = 69 vol%. The lower limit of the volume fraction thus obtained is given in Eq. 4 used:

The mole fraction of tantalum (X _C ) at 6.3 at% is thus outside the permitted limits: 22 at% <X _C <29.6 at%

B2 predominates in the resteutectic composition and forms after the Erstausscheidungen also the matrix. The dark areas (B2 phase) are connected to each other and are not present as single "islands". The overall proportion of the C14 phase is significantly lower than that of the B2 phase. shows the structure of Example 2 not according to the invention.

Example 3 Ta _8,5 Ni _49,5 Al ₄₂ (Fig. 8)

Step i

• Selection of the basic system: -> A = Al, B = Ni, C = Ta V _mC14 = 25.3 cm ³ / mol V _mB2 = 14.7 cm ³ / mol

Step ii

Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 56,9% = 43,1% ergibt V_B2eut = 43,1 vol% und überwiegt somit nicht in der Restschmelze. The mole fraction of tantalum in eutectic composition is in the above composition (Ni / Al = 1.2) at 14.5 at% ( ). Insertion in Eq. 1:

The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 56.9% = 43.1% V _B2eut = 43.1 vol% and thus does not predominate in the residual melt.

The C14 phase (bright areas in the ) predominates in a resteutectic composition and forms the matrix. It is good to see that the bright areas are connected. The B2 Erstausscheidungen (dark areas) exist as individual "islands". Non-inventive structure.

Example 4 Ta _24.3 Ni _41.3 Al _34.4 (Fig. 9)

Step i

• Selection of the basic system: -> A = Al, B = Ni, C = Ta V _mC14 = 25.3 cm ³ / mol V _mB2 = 14.7 cm ³ / mol

Step ii

Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 56,9% = 43,1% ergibt V_B2eut = 43,1 vol% und überwiegt somit nicht in der Restschmelze. The mole fraction of tantalum in eutectic composition is in the above composition (Ni / Al = 1.2) at 14.5 at% ( ). Insertion in Eq. 1:

The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 56.9% = 43.1% V _B2eut = 43.1 vol% and thus does not predominate in the residual melt.

Hypereutectic composition and greater nickel than aluminum content. The eutectic composition of the corresponding Konode has a tantalum content of about 14.5at%. The C14 phase predominates in the resteutectic composition and thus forms not only the initial precipitations but also the matrix. It is in the It is easy to see that the bright areas (C14 phase) are connected to each other and not as individual "islands". Non-inventive structure.

In summary, the conclusion can be drawn that a composition which adds up to 100 at% in the TaNiAl system always forms an inventive microstructure if the ratio of Ni to Al (Ni / Al) is between 0.66 and 1.1 and Proportion of tantalum between 21.0 at% and 29.6 at%. So Ta _21.0-29.6 NiAl with a ratio of Ni to Al (Ni / Al) between 0.66 and 1.1

In formula this can be described as follows: Ta _Xc Ni _Xb Al _Xa

System NbNiAl from step i:

• The molar volume of the C14 phase of the chosen basic system is: V _mC14 = 25.7 cm ³ / mol
• The molar volume of the corresponding B2 phase: V _mB2 = 14.7 cm ³ / mol

• • Anwendung von Schritt ii für Ni/Al = 0,66: Hier ist der Stoffmengenanteil von Niob in eutektischer Zusammensetzung Xc = 10 at% ( ). Entsprechend Schritt ii wird dieser Wert in Gl. 1 eingesetzt.
  
  Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 42,8% = 57,2% ergibt V_B2eut = 57,2 vol% und überwiegt somit in der Restschmelze.
• • Anwendung von Schritt ii für Ni/Al = 0,75: Hier ist der Stoffmengenanteil von Niob in eutektischer Zusammensetzung Xc = 12 at% ( ). Entsprechend Schritt ii wird dieser in Gl. 1 eingesetzt.
  
  Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 49,2% = 50,8% ergibt V_B2eut = 50,8 vol% und überwiegt somit in der Restschmelze.
• • Der maximale Stoffmengenanteil von Niob wird nach Schritt iii berechnet. Gl. 3 liefert:
  
• • Der minimale Niobgehalt ergibt sich anhand der eutektischen Zusammensetzung: 3. Anwendung von Schritt iii für die untere Grenze des Stoffmengenverhältnisses von Nickel zu Aluminium (Ni/Al = 0,66): V_B2eut = 57,2 vol% wird in die Formel zur Berechnung der unteren Grenze des C14 Volumenanteils eingesetzt: V_C14min = V_B2eut + 1/3·(V_C14max – V_B2eut) = 57,2 vol% + 1/3·(90 vol% – 57,2 vol%) = 68,1 vol%. Die so erhaltene untere Grenze des Volumenanteils wird in Gl. 4 eingesetzt:
  
  ergibt einen minimalen Stoffmengenanteil von Niob von 21,6 at% 4. Anwendung von Schritt iii für die obere Grenze des Stoffmengenverhältnisses von Nickel zu Aluminium (Ni/Al = 0,75): V_B2eut = 50,8 vol% wird in die Formel zur Berechnung der unteren Grenze des C14 Volumenanteils eingesetzt: V_C14min = V_B2eut + 1/3·(V_C14max – V_B2eut) = 50,8 vol% + 1/3·(90 vol% – 50,8 vol%) = 63,9 vol%. Die so erhaltene untere Grenze des Volumenanteils wird in Gl. 4 eingesetzt:
  
  ergibt einen minimalen Stoffmengenanteil von Niob von 20 at%

Structures according to the invention are set within the following stoichiometric limits:
The molar ratio of nickel to aluminum (Ni / Al) ranges from 0.66 to 0.75. The mole fraction of niobium is between 20.1 at% and 21.6 at% (depending on Ni / Al) and 29.6 at%

• • Application of step ii for Ni / Al = 0.66: Here, the mole fraction of niobium in eutectic composition is Xc = 10 at% ( ). According to step ii, this value is calculated in Eq. 1 used.
  
  The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 42.8% = 57.2% V _B2eut = 57.2 vol% and thus outweighs in the residual melt.
• • Application of step ii for Ni / Al = 0.75: Here, the mole fraction of niobium in eutectic composition is Xc = 12 at% ( ). According to step ii, this is in Eq. 1 used.
  
  The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 49.2% = 50.8% gives V _B2eut = 50.8 vol% and thus prevails in the residual melt.
• • The maximum mole fraction of niobium is calculated after step iii. Eq. 3 supplies:
  
• • The minimum niobium content is given by the eutectic composition: 3. Application of step iii for the lower limit of the molar ratio of nickel to aluminum (Ni / Al = 0.66): V _B2eut = 57.2 vol% is added to the formula Calculation of the lower limit of the C14 volume fraction used: V _C14min = V _B2eut + _1/3 · (V _C14max - V _B2eut ) = 57.2 vol% + _1/3 · (90 vol% - 57.2 vol%) = 68.1 vol%. The lower limit of the volume fraction thus obtained is given in Eq. 4 used:
  
  gives a minimum molar fraction of niobium of 21.6 at%. 4. Application of step iii for the upper limit of molar ratio of nickel to aluminum (Ni / Al = 0.75): V _B2eut = 50.8 vol% is expressed in the formula used to calculate the lower limit of the C14 volume fraction: V _C14min = V _B2eut + _1/3 · (V _C14max - V _B2eut ) = 50.8 vol% + _1/3 · (90 vol% - 50.8 vol%) = 63.9 vol%. The lower limit of the volume fraction thus obtained is given in Eq. 4 used:
  
  gives a minimum mole fraction of niobium of 20 at%

Here are two examples in the NbNiAl system. The alloys were produced by multiple remelting from the pure components in an arc melt. The micrographs are SEM images in the secondary electron image method. Compositions were determined in the REM by EDX.

Example 5 Composition Nb _24.3 Ni ₃₀ Al _44.7 (Fig. 12)

Step i

• Selection of the basic system: -> A = Al, B = Ni, C = Nb V _mC14 = 25.7 cm ³ / mol V _mB2 = 14.7 cm ³ / mol

Step ii

Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 42,8% = 57,2% ergibt V_B2eut = 57,2 vol% und überwiegt somit in der Restschmelze. The molar fraction of niobium in eutectic composition is in the above-mentioned composition (Ni / Al = 0.67) at 10 at% ( ). Insertion in Eq. 1:

The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 42.8% = 57.2% V _B2eut = 57.2 vol% and thus outweighs in the residual melt.

Step iii

V_B2eut = 57,2 vol% wird in die Formel zur Berechnung der unteren Grenze des C14 Volumenanteils eingesetzt: V_C14min = 57,2 vol% + 1/3·(90 vol% – 57,2 vol%) = 68,1 vol%. Die so erhaltene untere Grenze des Volumenanteils wird in Gl. 4 eingesetzt:

Der Stoffmengenanteil von Niob (X_C) mit 24,3 at% liegt somit innerhalb der Zulässigen Grenzen: 21,6 at% < X_C < 29,5 at% The upper limit for the mole fraction of niobium with Eq. 3 calculated:

V _B2eut = 57.2 vol% is used in the formula for calculating the lower limit of the C14 volume fraction: V _C14min = 57.2 vol% + _1/3 x (90 vol% - 57.2 vol%) = 68.1 vol%. The lower limit of the volume fraction thus obtained is given in Eq. 4 used:

The mole fraction of niobium (X _C ) at 24.3 at% is therefore within the permissible limits: 21.6 at% <X _C <29.5 at%

Significantly over-eutectic composition forms large C14 Erstausscheidungen (light phase). Due to the larger proportion of aluminum than nickel, the B2 phase (dark phase) predominates in the resteutectic and thus forms the matrix. Due to heterogeneous nucleation, the C14 portion of the resreutectic is predominantly attached to the C14 initial precipitates. The microstructure according to the invention is in the REM recording in to recognize.

Example 6 Nb _13.4 Ni _45.9 Al _40.7 (Fig. 13)

Step i

• Selection of the basic system: -> A = Al, B = Ni, C = Nb V _mC14 = 25.7 cm ³ / mol V _mB2 = 14.7 cm ³ / mol

Step ii

Der Volumenanteil der B2-Phase in eutektischer Zusammensetzung wird unter Verwendung von Gl. 2 berechnet. V_B2 = 100% – 56,8% = 43,2% ergibt V_B2eut = 43,2 vol% und überwiegt somit nicht in der Restschmelze. The mole fraction of niobium in eutectic composition is in the above composition (Ni / Al = 1.12) at 14.3 at%. Insertion in Eq. 1:

The volume fraction of B2 phase in eutectic composition is calculated using Eq. 2 calculated. V _B2 = 100% - 56.8% = 43.2% V _B2eut = 43.2 vol% and thus does not predominate in the residual melt.

With hypoeutectic composition, large initial B2 precipitations form (dark phase). Due to the larger proportion of nickel than aluminum, the C14 phase (light phase) predominates in the Resteutikumikum and thus forms the matrix. The non-inventive structure is in the REM recording in to recognize.

It can be summarized here for the system NbNiAl say that forms an inventive structure when the atomic composition supplementing 100 at% has a ratio of Ni to Al (Ni / Al) between 0.66 and 0.75 and the Proportion of Nb is between 20 at% and 29.5 at%. In formula, this finding can be expressed as follows: Nb _Xc Ni _Xb Al _Xa

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 60024189 T2 [0007]
• DE 2521563 A1 [0008]
• EP 0760869 B1 [0009, 0038]
• DE 102013214767 A1 [0010]

Cited non-patent literature

• Publication Gerhard Sauthoff "Intermetallics" ISBN: 978-3-527-61540-7 [0006]

Claims (8)

Structure of intermetallic B2 and C14 phases, characterized in that - the primary precipitated C14 phase forms substantially non-interconnected regions (islands), - the islands of the C14 phase are enclosed by the B2 phase, - the total volume the C14 phase in the structure outweighs that of the B2 phase. A method of making the structure of claim 1, comprising the following steps: i. Select one of the six basic systems NbNiAl, TaNiAl, TiNiAl, NbFeAl, TaFeAl and TiFeAl consisting of three different metals, A, B and C. Where A is aluminum (Al), B is iron (Fe) or nickel (Ni) and C is tantalum (Ta ), Niobium (Nb) or titanium (Ti), wherein metals A and B (AlNi and AlFe) form a B2 phase and metals A and B and C form a C14 phase. ii. Specification of the selection made in step i using Equation 1 (Equ. 1) and Equation 2 (Equ. 2) for those systems which, in eutectic composition, have a volumetric preponderance of the B2 phase relative to the C14 phase

V _B2 = 100% - V _C14 Eq. 2 with: V _mC14 = molar volume [m ³ / mol] of the C14 phase V _mB2 = molar volume [m ³ / mol] of the B2 phase V _C14 = volume fraction [%] of the C14 phase V _B2 = volume fraction [%] of the B2 Phase X _c = molar fraction of component C (for X _C the molar fraction of component C in eutectic composition is to be used V _B2 -> V _B2eut ) iii. To ensure that the volume fraction of the C14 phase is within the following limits using equation 3 (equation 3) and equation 4 (equation 4): upper limit: V _C14max = 90 vol.% _Of the total volume lower limit: V _C14min = V _B2-eut + _1/3 · (V _{C14max -V B2eut} )

where the molar fraction of component C (X _C ) is: X _minC <X _C <X _maxC Microstructure according to claim 1 or prepared according to the method of claim 2, characterized in that it is formed by the metals aluminum, nickel and tantalum (TaNiAl) or aluminum, nickel and niobium (NbNiAl). Microstructure according to Claim 3, characterized in that the atomic composition Ta _21.0-29.6 NiAl , which is complementary to 100 at%, has a ratio of Ni to Al (Ni / Al) between 0.66 and 1.1 or Nb _20-29.5 NiAl with a ratio of Ni to Al (Ni / Al) is between 0.66 and 0.75. Microstructure according to claim 3 and 4, wherein the two systems TaNiAl and NbNiAl have the following composition, Ta _Xc Ni _Xb Al _Xa

Nb _Xc Ni _Xb Al _Xa

Microstructure according to claim 3, 4 and 5, wherein the two systems TaNiAl and NbNiAl have the following composition: Ta _22.5 Ni _35.9 Al _41.6 Nb _24.3 Ni ₃₀ Al _44.7 Use of the structure according to one of the preceding claims as a high temperature loaded component of a gas turbine. Use of the structure according to one of the preceding claims 1, 3, 4, 5 and 6 as a high-temperature material for dies for the production of articles which require high strength, high heat resistance.

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