Method for obtaining products made of titanium alloys or titanium-aluminum intermetallic compounds

Abstract

This invention relates to a method for obtaining a product made of a titanium alloy or a titanium-aluminum intermetallic compound by melting with a plasma torch, the alloy having an oriented structure, the method comprising: heating a molten alloy (1) in a casting ring (2) by means of a plasma torch (3); cooling a cold zone (21) of length L1 of the casting ring, the cooling forming a semi-solid crown (12) of the alloy; heating a hot zone (22) of length L2 of the casting ring to form a solidification front (13), the solidification front having a flatness of less than 10° relative to a plane perpendicular to the stretching direction; and at a greater than 10° angle in the stretching direction... ‑4 The invention also relates to an apparatus for carrying out the method. (14) The alloy is solidified by stretching at a speed of m / s.

Description

Technical Field

[0001] This invention relates to methods for manufacturing alloys, particularly aerospace alloys such as titanium-based alloys or TiAl intermetallic compounds, and to the field of equipment for carrying out these methods. Background Technology

[0002] Several processes exist for manufacturing alloys, particularly aerospace alloys such as nickel-based alloys, titanium-based alloys, or TiAl intermetallic alloys. The latter are primarily made from pure raw materials, which are compacted in the form of cylindrical electrodes and then melted in a vacuum arc remelting process (more commonly known as VAR), or by recycling scrap materials, with vacuum induction melting (more commonly known as VIM) most commonly used for recycling scrap materials (in a cold crucible or a hot crucible).

[0003] However, for intermetallic alloys containing approximately 50% aluminum atoms, these methods have the disadvantage of being carried out under vacuum. Considering the vapor pressure of aluminum in a molten titanium bath, a significant amount of aluminum may evaporate during melting, making it difficult to control the overall alloy composition.

[0004] For these alloys, and especially for titanium-based alloys, alternative methods exist and are still being developed, namely plasma torch melting in a cold crucible (or PAM-CHR, which stands for plasma arc melting / cold hearth refining). Figure 1 This method is illustrated in the figure. This method uses helium and / or argon to feed the plasma torch at atmospheric pressure. The neutral gas pressure allows the evaporation of reactive elements containing aluminum to be limited to three to five orders of magnitude, making it possible to melt such alloys. More specifically, in this method, the raw material MP (which may be in the form of scrap, briquettes, bars, or sponge / master alloy mixtures) is pushed into a cold crucible CR and melted by scanning the surface of the crucible with one or more plasma torches TC. As melting proceeds, the liquid metal AF moves toward a refining zone where the temperature stabilizes and some impurities are removed. The liquid metal AF then flows discontinuously into a cooling casting ring AM, which is made of copper, and from which the ingot L is progressively extracted.

[0005] From an economic perspective, the PAM-CHR method is one of the cheapest titanium remelting processes (reducing costs by 20% to 60%): it also allows for easy recycling of scrap without the need for pre-compacting the scrap; and the use of a plasma torch to concentrate energy where needed makes the process more energy-efficient. In some cases, the material health of the resulting ingots makes it possible to use the material without any additional thermomechanical conversion treatment, and to cut parts directly from its bulk.

[0006] However, for some alloys, such as titanium-based alloys and TiAl intermetallic alloys, the microstructure, especially its orientation, can directly affect the mechanical properties of the resulting alloy. Therefore, microstructure control during solidification is a key area requiring improvement in these alloys. In the case of PAM-CHR, solidification primarily occurs at the casting ring, which is now made of cooled copper.

[0007] The PAM-CHR method is close to the continuous casting techniques well-known in the art. However, solutions exist that make it possible to orient the microstructure during solidification in these continuous casting processes. Most solutions are based on the use of two regions, which are, in sequence, a hot region where the metal remains liquid and a cold region where the metal cools.

[0008] However, these solutions cannot be directly applied to the PAM-CHR method. In fact, the latter has unique characteristics regarding the casting ring, including the use of a plasma torch to heat the surface of the liquid metal above the casting ring, which is typically centered relative to the casting ring. This configuration generates a heat flux at the surface of the liquid bath, which, for casting cylindrical ingots with a circular base, can be modeled according to Equation 1, where η is the torch efficiency, Q is its power (W), σ is the torch's radius of influence (m), and r is the distance from the center of the ingot (m):

[0009] [Equation 1]

[0010]

[0011] Such heat flux distribution associated with the ingot's stretching rate is incompatible with directional solidification because it creates a non-planar solidification front at the casting ring; deeper at the center of the ring than at its edges. Figure 2 This refers to the cross-section of an ingot cast using this type of process. Figure 3 An example of a solidification front obtained using this type of method is shown schematically.

[0012] The authors of document FR 3090430 attempted to address these inhomogeneities. In this document, the mixing of liquid alloy in a casting ring is achieved through electromagnetic induction, making it possible to homogenize and optimize the macroscopic structure of the obtained ingot, and facilitating the transformation of this ingot to obtain the final part. Furthermore, the method described in this document makes it particularly possible to reduce deviations in the (e.g., mechanical) properties of the obtained ingot.

[0013] However, the method described in this literature has the drawback of not being able to orient the microstructure. In fact, the agitation generated inside the liquid alloy makes it impossible to control the solidification front; induction generates agitation that is detrimental to the directional growth of dendrites. Summary of the Invention

[0014] This disclosure improves upon the aforementioned situation.

[0015] To this end, the present invention provides a method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting, wherein the alloy has an oriented structure, the method comprising:

[0016] - A plasma torch that heats the surface of a molten alloy at a casting ring;

[0017] - A cold region of length L1 is cooled directly below the surface of the molten alloy at the casting ring, thereby forming a semi-solid crown of the alloy;

[0018] - Downstream of the cold zone, the hot zone of length L2 is heated, thereby allowing control of the solidification front of the alloy at the exit of the hot zone, with a flatness of less than 10° relative to a plane perpendicular to the stretching direction; and

[0019] Along the stretching direction at a value greater than 10 -4 The alloy is solidified by stretching at a speed of m / s.

[0020] In this disclosure, when the alloy comprises at least 50% titanium by weight, the alloy is referred to as a "titanium alloy" or "titanium-based alloy".

[0021] Thanks to the formation of a solidification front perpendicular to the stretching direction of the alloy ingot, it is possible to obtain an oriented structure. This makes it possible to improve the properties of the alloy in question, particularly its mechanical properties, allowing parts to be machined directly in the ingot without preliminary treatment.

[0022] Optional and non-restrictive features are disclosed in this paper.

[0023] The cold zone can be maintained at a temperature between 0°C and 50°C, preferably between 10°C and 40°C, preferably between 25°C and 35°C, preferably between 20°C and 30°C, and preferably 25°C.

[0024] The hot region can be maintained at a temperature between T f ×0.8 and T f Between ×1.25, preferably T f ×0.85 and T f Between ×1.20, preferably T f ×0.9 and T f Between ×1.15, preferably T f With T f Between ×1.10, preferably T f ×1.05. In this article, T... f Let be the melting point of the alloy under consideration.

[0025] The length L1 can be between 0.065 m and 0.09 m.

[0026] The length L2 can be between 0.17 m and 0.3 m.

[0027] The ratio of L2 / L1 can be between 4 and 6, preferably 5.

[0028] The power of the plasma torch can be selected based on the stretching speed and is governed by the following Equation 2, where V is the stretching speed (m / s), S is the cross-section of the stretched ingot (m²), R is the radius of the stretched ingot (m), η is the efficiency of the plasma torch, Q is the power of the plasma torch (W), σ is the effective radius of the plasma torch (m), P is the circumference of the casting ring (m), L is the total length of the casting ring (m), and ρ is the bulk mass of the casting alloy (kg / m³). -3 h is the exchange coefficient of the casting ring (Wm) -2 .℃ -1 ), L M The specific latent heat of melting of the cast alloy (J·kg) -1 ), C P Specific heat (J·kg) -1 .℃ -1 ), where ΔT2 is the thermal gradient (°C) between the inlet and outlet of the ring, and ΔT1 is the thermal gradient between the metal temperature in the hot region and its preheating temperature:

[0029] [Equation 2]

[0030] .

[0031] In Equation 2 above, ΔT1 can be between 10℃ and 250℃, and ΔT2 can be between 200℃ and 900℃, especially for TiAl intermetallic alloys.

[0032] The method may further include cooling a second cold region, with a length L3 downstream of the hot region. In this case, the length L3 may be greater than 0.03 m.

[0033] The present invention also relates to an apparatus for obtaining products made of titanium alloys or titanium intermetallic compounds by plasma torch melting, the alloys having an oriented structure, the apparatus comprising:

[0034] -Plasma torch;

[0035] - A cast ring having an alloy inlet end and an alloy outlet end, the inlet end being positioned below the plasma torch;

[0036] - A cooling device, positioned around the casting ring near the inlet end; and

[0037] - A heater, which is placed around the casting ring between the cooling device and the alloy outlet end. Attached Figure Description

[0038] Other features, details, and advantages will become apparent when reading the detailed description below and when analyzing the accompanying drawings, in which:

[0039] Figure 1

[0040] [ Figure 1 The diagram illustrates the existing PAM-CHR method.

[0041] Figure 2

[0042] [ Figure 2 [Indicates passing] Figure 1 The cross section of the tensile ingot was obtained by the method.

[0043] Figure 3

[0044] [ Figure 3 [Illustrative demonstration of use] Figure 1 An example of a solidification front obtained by the method.

[0045] Figure 4

[0046] [ Figure 4 The diagrams illustrate an example of a method according to the invention, the diagrams being limited to portions different from those of the prior art. Figure 4 In this method, the hot zone downstream of the cold zone is used in the casting ring.

[0047] Figure 5

[0048] [ Figure 5 The diagram illustrates another example of the method according to the invention. Similar to... Figure 4 The diagram is limited to parts that differ from the prior art. Figure 5 Methods and Figure 4 The difference in this method is that another cold zone is added downstream of the hot zone.

[0049] Figure 6

[0050] [ Figure 6 The angle α formed by the solidification front relative to the plane perpendicular to the stretching direction is shown as a function of the lengths L1 of the cold region and L2 of the hot region at a stretching speed of 0.00015 m / s.

[0051] Figure 7

[0052] [ Figure 7 The angle α formed by the solidification front relative to the plane perpendicular to the stretching direction is shown as a function of the lengths L1 of the cold region and L2 of the hot region at a stretching speed of 0.0003 m / s.

[0053] Figure 8

[0054] [ Figure 8 The angle α formed by the solidification front relative to the plane perpendicular to the stretching direction is shown as a function of the lengths L1 of the cold region and L2 of the hot region at a stretching speed of 0.00045 m / s.

[0055] Figure 9

[0056] [ Figure 9 The image shows the angle α formed by the solidification front relative to the plane perpendicular to the stretching direction for a cold region length L1 of approximately 0.077 m at a stretching speed of 0.0003 m / s, as the lengths L2 and L3 of the hot region change.

[0057] In the above Figures 6 to 9 In the diagram, lines represent the junctions of contour lines with the same angle value. Solid lines indicate the boundaries between regions with angles greater than 10° and regions with angles less than 10°. The darker the pattern, the larger the angle.

[0058] Figure 10

[0059] [ Figure 10 The grayscale image schematically illustrates the state of the alloy within the casting ring that forms a solidified crown at the periphery (white - 0.0 - if the alloy is completely liquid, black - 1.0 - if the alloy is completely solid); the horizontal axis indicates the distance from the surface of the molten alloy (L). S ), and the vertical axis indicates the distance from the center of the longitudinal axis of the casting ring and the ingot (L). R ).

[0060] Figure 11

[0061] [ Figure 11 [This section demonstrates an apparatus for implementing the method according to the invention.] Detailed Implementation

[0062] The following will refer to Figures 4 to 9The method according to the invention for obtaining products made of titanium alloys or TiAl intermetallic compounds by plasma torch melting is described in more detail. The alloys obtained by this method have an oriented structure. When a range of values ​​is given for a given characteristic, the range within the two disclosed endpoints also constitutes part of the invention; any disclosed lower endpoint may be selected as the lower or upper endpoint of the range, and any disclosed upper endpoint may be selected as the lower or upper endpoint of the range, the only limitation being that the value selected as the lower endpoint should be lower than the value selected as the upper endpoint.

[0063] This method includes: heating the surface 11 of the molten alloy 1 at the casting ring 2 using a plasma torch 3; cooling a cold region 21 of length L1 directly below the surface 11 of the molten alloy 1 at the casting ring 2; heating a hot region 22 of length L2 downstream of the cold region 21; and along the stretching direction. With more than 10 -4 The alloy is solidified by stretching at a speed of m / s.

[0064] The power of the plasma torch 3 during the heating of the surface 11 of the molten alloy 1 can be selected based on the stretching speed. Conversely, the selection of the stretching speed can be based on the power of the plasma torch 3. In particular, this selection can be governed by the controlling law expressed by Equation 2 above. Those skilled in the art will know how to reverse these expressions to express the desired power as a function of the stretching speed.

[0065] These equations are particularly suitable for circular cross-sections of stretched ingots. However, the equations also apply to ingots with different shapes, especially square, triangular, or rectangular cross-sections. In fact, the equations provide a good approximation of the control laws for ingots with other cross-sectional shapes. Furthermore, it should be noted that the greater the stretching speed, the lower the power of the plasma torch capable of maintaining the molten alloy. This is especially true when the cross-section of the ingot being produced is large.

[0066] Preferably, the power of the plasma torch is between 5 kW and 400 kW.

[0067] Cooling the cold region 21 makes it possible for alloy 1 to solidify locally and produce a semi-solid alloy crown 12. Figure 10 (As shown in the diagram). This semi-solid crown 12 shields the heterogeneous heat flux of the plasma torch 2, thereby enabling controlled heating downstream of this region. The cold region 21 can be maintained at a temperature between 0°C and 50°C, preferably between 10°C and 40°C, preferably between 25°C and 35°C, preferably between 20°C and 30°C, and preferably 25°C.

[0068] Cooling of the cold zone 21 can be achieved through an active cooling system. An exemplary active cooling system may include a cooling loop comprising a heat exchange zone with a heat transfer fluid; the heat exchange zone is positioned at the cold zone of the casting ring 2. This exchange zone may be made, for example, by winding a copper tube through which the flow of water is controlled at a constant temperature, and comes into contact with a portion of the casting ring 2 to be cooled. This can also be accomplished by forming a cavity in the cold zone of the casting ring 2 to allow fluid to flow therein, thereby achieving heat dissipation.

[0069] The use of a hot region 22 downstream of the cold region 21 makes it possible to liquefy the alloy 1 again, this time in a controlled manner. Therefore, a semi-solid cavity (an alloy in a paste-like form) is formed below the crown 12, the temperature and location of which can be easily controlled; this allows for control of the solidification front 13. Thus, thanks to this combination of the cold region 21 and the hot region 22 downstream of it, it is possible to control the flatness of the solid / liquid interface of the alloy as it cools. Therefore, it is possible to control the solidification front 23 of the alloy formed in the hot region relative to the direction perpendicular to the stretching direction. The angle α of the plane is such that the angle is kept below 10°. The angle is measured at the inner surface of the casting ring 2 in a plane including the longitudinal axis of the stretched ingot, which is collinear with the stretching direction; this angle is the angle between the line formed by the intersection of the considered plane and a plane perpendicular to the stretching axis, and the tangent to the curve formed by the intersection of the considered plane and the considered solidification front at the inner surface of the casting ring 2. Furthermore, the alloy is in a paste-like and non-liquid form, which makes it possible to limit the erosion of the casting ring by the molten alloy.

[0070] The temperature of the hot region 22 has a direct impact on the flatness of the solidification front 13. Therefore, the hot region 22 is preferably maintained at a temperature between T and T. f ×0.8 and T f Between ×1.25, preferably T f ×0.85 and T f Between ×1.20, preferably T f ×0.9 and T f Between ×1.15, preferably T f With T f Between ×1.10, preferably T f ×1.05. T f This refers to the melting point of the alloy. These ranges are valid for all geometries of stretched ingots.

[0071] The heated area can be heated by induction heating, resistance heating, or radiation heating. In the case of induction heating, the heated area of ​​the cast ring must be made of a ferromagnetic material and its size must be predetermined to prevent the inductive force from being transmitted to the alloy. In practice, in such cases, the alloy is then activated by the inductive force, disrupting its solidification into an oriented structure.

[0072] The length L1 of the cold region 21 can be between 0.065 m and 0.09 m. The length L2 of the hot region 22 can be between 0.17 m and 0.3 m.

[0073] The lengths L1 and L2 have been determined through simulation, enabling the assessment of the flatness of the solidification front. Figures 6 to 8 The figures present some results obtained for a cross-section of a 78 cm² stretched circular ingot. These figures show the effect of the choice of lengths L1 and L2 on the flatness of the solidification front at different stretching velocities of 0.00015 m / s, 0.0003 m / s, and 0.00045 m / s, respectively. The flatter the solidification front, the shallower the corresponding domain. It can be noted that the higher the stretching speed, the more limited the domain corresponding to the solidification front forming an angle of less than 10° relative to the plane perpendicular to the stretching direction. Length ranges have been determined to achieve a good trade-off between the flatness of the solidification front and the range of stretching speeds suitable for the method.

[0074] The L2 / L1 ratio between the length of the hot region 22 and the length of the cold region 21 can be between 4 and 6, preferably 5. In these cases, the ratio G / V between the thermal gradient at the solid / liquid interface of the alloy (pasty region) and the rate of progress of the solidification front is greater than 10. 6 Ks / m². These ratios correspond to the regions that promote directional solidification.

[0075] To further increase the G / V ratio, the method may further include a second cold region 23 downstream of the hot region 22, with a cooling length L3. Such a method is illustrated in... Figure 5 In, among which, besides those already existing Figure 4 In addition to the components in the hot zone 22, a second cold zone 23 is added downstream. In this case, the length L3 can be greater than 0.03 m. This limitation has been determined through simulation. Figure 9 The results of one of these simulations for a tensile velocity of 0.0003 m / s are presented. It should be noted that L3 requires more than 0.03 m to find an increasing domain with an angle greater than 10°. On the other hand, beyond 0.06 m, this domain no longer grows.

[0076] Upstream of the steps described above, the method may include: supplying raw materials (especially in the form of scrap, briquettes, rods, sponge / master alloy mixtures, etc.), heating the raw materials (e.g., by plasma torch, electric arc, induction, electron bombardment, etc.) to melt the raw materials into a rough molten alloy, refining the rough molten alloy (including, for example, stabilizing the temperature of the alloy and removing impurities), and casting the refined molten alloy into a casting ring 2. These steps are known from the prior art and do not constitute the core of this invention.

[0077] The following text is for reference only. Figure 11 An apparatus according to the invention is described for obtaining titanium alloys or titanium intermetallic products by melting with a plasma torch, the alloys having an oriented structure. The apparatus 10 includes a plasma torch 3, a casting ring 2, a cooling device 4, and a heater 5.

[0078] The casting ring 2 has an alloy inlet end 24 and an alloy outlet end 25, with the inlet end 24 positioned below the plasma torch 3. The casting ring 2 includes a cold region 21 positioned below the inlet end 24 and a hot region 22 positioned downstream of the cold region 21, in particular in contact with the latter. The casting ring 2 may further include a second cold region 23 downstream of the hot region 22 and above the outlet end 25.

[0079] At least a portion of the cooling device 4 is positioned around the cold region 21 of the casting ring 2. This cooling device may include a cooling circuit comprising a heat exchanger positioned around the cold region 21 of the casting ring 2. Alternatively, this device may consist of windings of copper pipes that circulate cooling fluid.

[0080] The heater 5 is positioned between the cooling device 4 and the outlet end 25, surrounding the hot zone 22 of the casting ring 2. This device can be formed by a magnetic inductor that allows coupling with the constituent material of the hot zone of the casting ring.

[0081] The apparatus may also include controls for controlling the power of the plasma torch 3 according to the stretching speed. Alternatively, the control may be based on the stretching speed of the plasma torch 3. These controls may be performed according to Equation 2 above.

[0082] When the casting ring 2 includes a second cold zone 23, this zone can be passively cooled by heat exchange with ambient air. Alternatively, a second cooling device 6 may be provided, a portion of which is positioned around the second cold zone 23. This second cooling device 6 may be selected from the same options as cooling device 4.

[0083] The apparatus 10 may also include a cold crucible 7 for receiving raw materials and placed above the casting ring 2. The apparatus 10 may further include a heater 8 for heating the raw materials until they melt. Heating may be plasma torch heating, electric arc heating, induction heating, electron bombardment heating, etc. Heating may also be performed via an electron beam melting (EB torch) process.

[0084] The device may include sensors for controlling the stretching speed. The device may also include sensors for controlling the temperature of the cooling device 4 (e.g., the heat transfer fluid).

Claims

1. A method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting, said alloy having an oriented structure, the method comprising: - Plasma torch (3), which heats the surface (11) of the molten alloy (1) at the casting ring (2); - A cold region (21) of length L1 is cooled directly below the surface of the molten alloy at the casting ring, thereby forming a semi-solid crown (12) of the alloy. Downstream of the cold region, a hot region (22) of length L2 is heated, thereby controlling the solidification front (13) of the alloy at the outlet of the hot region, and achieving a flatness of less than 10° relative to a plane perpendicular to the stretching direction; and Along the stretching direction at a rate greater than 10 -4 The alloy (14) is solidified by stretching at a speed of m / s, wherein the cold region is maintained at a temperature between 0°C and 50°C, and wherein the hot region is maintained at a temperature between T f ×0.8 and T f Between ×1.25, T f This indicates the melting temperature of the alloy under consideration.

2. The method according to claim 1 for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting, characterized in that, The length L1 is between 0.065 m and 0.09 m.

3. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, The length L2 is between 0.17 m and 0.3 m.

4. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, The L2 / L1 ratio is between 4 and 6.

5. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, The ratio of L2 to L1 is 5.

6. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, The power of the plasma torch is selected based on the stretching speed and is governed by the following equation, where V is the stretching speed (m / s), S is the cross-section of the stretched ingot (m²), R is the radius of the stretched ingot (m), η is the efficiency of the plasma torch, Q is the power of the plasma torch (W), σ is the effective radius of the plasma torch (m), P is the circumference of the casting ring (m), L is the total length of the casting ring (m), and ρ is the volumetric mass of the casting alloy (kg / m³). -3 h is the exchange coefficient (Wm) of the cast ring. -2 .℃ -1 ), C P Specific heat (J·kg) -1 .℃ -1 ), L M The specific latent heat of the casting alloy (J·kg) -1 ), where ΔT2 is the thermal gradient (°C) between the inlet and outlet of the ring, and ΔT1 is the thermal gradient between the metal temperature and its preheating temperature in the hot region: 。 7. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, further comprising cooling a second cold region of length L3 downstream of the hot region.

8. The method according to claim 7 for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting, characterized in that, The length L3 is greater than 0.03 m.

9. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, Along the stretching direction at a rate greater than 10 -4 When the alloy (14) is stretched at a speed of m / s, the cold region is maintained at a temperature between 10°C and 40°C.

10. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, Along the stretching direction at a rate greater than 10 -4 When the alloy (14) is stretched at a speed of m / s, the cold region is maintained at a temperature between 25°C and 35°C.

11. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, Along the stretching direction at a rate greater than 10 -4 When the alloy (14) is stretched at a speed of m / s, the cold region is maintained at a temperature between 20°C and 30°C.

12. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, Along the stretching direction at a rate greater than 10 -4 When the alloy (14) is stretched at a speed of m / s, the cold region is maintained at a temperature of 25°C.

13. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, Along the stretching direction at a rate greater than 10 -4 When the alloy (14) is stretched and solidified at a speed of m / s, the hot zone is maintained at a temperature between T and T. f ×0.85 and T f Between ×1.

20.

14. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, Along the stretching direction at a rate greater than 10 -4 When the alloy (14) is stretched and solidified at a speed of m / s, the hot zone is maintained at a temperature between T and T. f ×0.9 and T f Between ×1.

15.

15. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, Along the stretching direction at a rate greater than 10 -4 When the alloy (14) is stretched and solidified at a speed of m / s, the hot zone is maintained at a temperature between T and T. f With T f Between ×1.

10.

16. The method for obtaining a product made of titanium alloy or TiAl intermetallic compound by plasma torch melting according to any one of claims 1 to 2, characterized in that, Along the stretching direction at a rate greater than 10 -4 When the alloy (14) is stretched and solidified at a speed of m / s, the hot zone is maintained at a temperature of T. f ×1.05.

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