JP6792837B2 - Titanium-aluminum alloy - Google Patents

Description

The present invention relates to a titanium-aluminum alloy having improved ductility (elongation) at room temperature.

The titanium-aluminum alloy is a lightweight heat-resistant material having a specific gravity (<4.0) less than half that of the nickel-based superalloy, and has the property of being extremely suitable for use at high temperatures. , Used in turbine blades, engine valves, hot air ventilators, etc. in aircraft engines and stationary gas turbines.

In the case of turbine blades using titanium-aluminum alloy as an example, most of them are conventionally manufactured by the precision casting (lost wax) method. The outline of the precision casting method referred to here is as follows. First, a wax mold for a turbine blade is manufactured in advance, a mold is prepared based on the wax mold, then dewaxing and firing are performed, the turbine blade is cast, and the surrounding mold is cut off to complete the process. ..

However, the precision casting method can produce not only turbine blades but also other titanium-aluminum alloy products such as parts such as engine valves and hot air ventilators. However, there are concerns that the titanium-aluminum alloy material and the reactor may cause contamination, the surface oxidation of the titanium-aluminum alloy material itself, and the wear resistance due to surface cutting during product finishing may be affected. Further, the titanium-aluminum alloy itself produced by a known method such as a precision casting method has a ductility at room temperature (up to about 50 ° C. or lower) (hereinafter referred to as "room temperature ductility") of about 1%. For example, it has poor room temperature ductility as compared with nickel-based superalloys and the like. Therefore, there were concerns about mass production and commercialization of turbine blades themselves and parts of engine valves and hot air ventilation systems.

Such concerns, particularly titanium-aluminum alloys with improved room temperature ductility, are disclosed, for example, in Japanese Patent No. 4476637 (Patent Document 1). The titanium-aluminum alloy described in Patent Document 1 contains niobium, molybdenum, carbon and boron in addition to titanium and aluminum which are the bases of the alloy.

Regarding the improvement of room temperature ductility of titanium-aluminum alloys, in recent years, research and development focusing on the fine (micro) structure of titanium-aluminum alloys have been carried out. A titanium-aluminum alloy having improved room temperature ductility by focusing on such a fine (micro) structure is disclosed in, for example, Japanese Patent Application Laid-Open No. 2014-227601 (Patent Document 2).

Generally, the titanium-aluminum alloy has a roughly two-phase structure of TiAl phase (γ phase) and Ti ₃ Al (α ₂ ) phase. Further, the titanium-aluminum alloy has a single γ phase structure (a structure composed of equiaxed grains of almost γ monophase), a lamella structure in which γ phase and α ₂ phase form a layered structure, equiaxed fine grains of γ phase, and γ. It has a structure such as a duplex structure composed of both fine particles having a / α ₂ lamella structure. By the way, these structures change depending on the heat treatment temperature and the composition ratio of titanium and aluminum. When a titanium-aluminum alloy is applied to a turbine blade or the like, the fine (micro) structure related to the strength of the product largely depends on the lamella structure or the duplex structure. Above all, the room temperature ductility depends on the duplex structure (see, for example, Japanese Patent Application Laid-Open No. 10-237567 presented as Patent Document 3).

Japanese Patent No. 4476637 Japanese Unexamined Patent Publication No. 2014-227601 Japanese Unexamined Patent Publication No. 10-237567

However, the room temperature ductility of the titanium-aluminum alloy described in Patent Document 1 depends on other niobium and molybdenum, as well as carbon and boron, rather than the underlying titanium and aluminum, and the microstructure of the titanium-aluminum alloy. There is no disclosure or suggestion about. Regarding the alloy (ingot) described in Patent Document 2, only the lamella structure was modified for the microstructure, and there was no disclosure or suggestion for the duplex structure, and the patent for improvement of room temperature ductility was made. Similar to Document 1, it depends on other metals, carbon and silicon rather than the base titanium and aluminum. Further, as described above, Patent Document 3 describes the relationship between the duplex structure and the room temperature ductility, but in the end, the target alloy depends on the lamella structure (structure) for the room temperature ductility, and the target alloy. It is suggested that the relationship between the duplex structure and the room temperature ductility in the above is rather poor (see Comparative Example of Patent Document 3).

Even if Patent Documents 1 to 3 are fully utilized, the relationship between the duplex structure and room temperature ductility is not clarified.

In view of the above circumstances, the present invention mainly provides a titanium-aluminum alloy having improved ductility (elongation) at room temperature in consideration of the duplex structure (layer), the soft layer, and the laminated structure of these layers.

An object of the present invention is that in a titanium-aluminum alloy, the titanium-aluminum alloy is composed of a hard layer having a duplex structure and a soft layer made of γ monophasic equiaxed grains, and the hard layer and the soft layer are composed of the hard layer and the soft layer. has a laminated structure alternately, and shaping angle, Ri 40 ° to 60 ° der, and the titanium - effect by room temperature ductility of the aluminum alloy characterized in that it is a 2 to 3.5% Achieved

The hard layer, by a 1.1 to 3 times the size of the soft layer, the composition concentration of some stomach aluminum, by a 45～49At%, is more effectively achieved.

In the titanium-aluminum alloy according to the present invention, ductility at room temperature and various strength improvements could be achieved by considering the layer structure of the hard layer and the soft layer and the lamination molding angle thereof.

It is the schematic which shows the laminated structure of the titanium-aluminum alloy of this invention. It is a schematic diagram which shows the state when the rectangular piece is cut out from the titanium-aluminum alloy which concerns on this invention at every molding angle (modeling angle θ = 0 °). It is a schematic diagram which shows the state when the rectangular piece is cut out from the titanium-aluminum alloy which concerns on this invention for each molding angle (the molding angle θ varies from 0 ° to 90 °. However, 0 ° and 90 ° are excluded). It is a schematic diagram which shows the state when the rectangular piece is cut out from the titanium-aluminum alloy which concerns on this invention at every molding angle (modeling angle θ = 90 °). It is a figure which shows the outline of each test piece which concerns on Comparative Examples 1 and 2 and Example 1. FIG. It is an optical microscope image which shows the surface of each test piece which concerns on Comparative Examples 1 and 2 and Example 1. FIG. It is a graph which describes the relationship between the molding angle which concerns on each test piece which concerns on Comparative Examples 1 and 2 and Example 1, and ductility (%). It is an optical microscope image and schematic diagram which shows the state of deformation of the soft layer which concerns on Example 1 (modeling angle θ = 45 °). It is a graph which described the relationship between the molding angle which concerns on each test piece which concerns on Comparative Examples 1 and 2 and Example 1, and a yield stress (MPa). 6 is a scanning electron microscope image showing the surface of each test piece according to Examples 1, 2 and 3. It is a graph which described the relationship between the molding angle which concerns on each test piece which concerns on Examples 1, 2 and 3 and ductility (%). 6 is a scanning electron microscope image showing the surface of each test piece according to Examples 1, 4 and 5. It is a graph which describes the ductility (%) of each test piece which concerns on Examples 1, 4 and 5.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing a laminated structure of a titanium-aluminum alloy of the present invention. Further, arrow A in FIG. 1 indicates a direction in which a mixed powder of titanium and aluminum or a titanium-aluminum alloy powder is laminated. As shown in FIG. 1, the titanium-aluminum alloy 1 of the present invention is formed by alternately laminating hard layers 2 and soft layers 3.

Next, the hard layer 2 in the laminated structure of the titanium-aluminum alloy 1 of the present invention shown in FIG. 1 will be described.

In general, with regard to strength, as described above in the background technology section, a lamellar structure in which the TiAl (γ) phase and the Ti ₃ Al (α ₂ ) phase form a layered structure, or γ single-phase equiaxed grains and γ / alpha is large to rely on the duplex structure composed of fine grains having ₂ lamellar structure.

Here, it is desirable that the hard layer 2 forming the laminated structure of the titanium-aluminum alloy according to the present invention mainly has a duplex structure.

Next, the soft layer 3 forming the laminated structure of the titanium-aluminum alloy according to the present invention will be described.

In principle, the soft layer 3 forming the laminated structure of the titanium-aluminum alloy according to the present invention is preferably composed of γ single-phase equiaxed grains. However, if the content is 2% or less with respect to the equiaxed particles of the γ single phase, mixing of fine particles (fine particles) of the α ₂ phase is allowed. Incidentally, mixing fine particles of alpha ₂ phase becomes more than 2%, there is a concern that the ductility is lowered. Further, if the mixture of α _2- phase fine particles is more than 2%, γ single-phase equiaxed particles may not be obtained.

Incidentally, the thickness _{T 1} of the hard layer 2, the ratio of the thickness _{T 2} of the soft layer _3, T 1 = _{1.1~3T 2,} i.e. the thickness _{T 1} is, becomes 1.1 to 3 times the thickness _{T 2} Is desirable. If it is less than 1.1 times, the strength decreases. On the contrary, when it is 3 times or more, the ductility decreases, but the strength increases. In this specification, as embodiments of the invention, the thickness T ₁ of the hard layer 2, although the ratio of the thickness T ₂ of the soft layer 3 was noted, for example the size of each layer (area And volume) may be the parameter.

Further, in the titanium-aluminum alloy 1 of the present invention, the composition ratio of titanium and aluminum is such that α ₂ phase and γ phase and a mixed structure (γ / α ₂ mixed structure) thereof can be formed. Moreover, there is no particular limitation as long as the structure is such that the hard layer 2 and the soft layer 3 are alternately laminated as shown in FIG. However, in order to form the structure, it is desirable that the composition (concentration) of aluminum is 45 to 49 at% (atomic composition percentage). The concentration of aluminum is less than 45at%, the proportion of alpha ₂ phase is increased, duplex tissues and equiaxed γ single phase structure is not formed. Further, even more than 49At%, since the alpha ₂ phase is not present, the duplex structure is not formed. Incidentally, when the concentration of aluminum is 45 to 49 at%, the remainder is formed of titanium and a third element described later, and the composition (concentration) of titanium is not particularly limited. Not limited to the present invention, titanium-aluminum alloys generally contain a third element (additional element), but the composition ratio of the third element is also related to the titanium-aluminum according to the present invention. There is no particular limitation as long as it does not affect the laminated structure of the alloy. By the way, the third element (additional element) referred to here is a Group 5-7 element such as chromium, niobium, vanadium, molybdenum, tungsten, manganese, etc., a Group 15 element such as carbon and silicon, titanium and An element of the same family as each of aluminum.

Further, in the production of the titanium-aluminum alloy 1 of the present invention, a layered manufacturing method in which powders alloyed with titanium and aluminum are laminated is adopted, but the type of the layered manufacturing method is not particularly limited, for example, heat treatment or heat treatment. Any conventional technique such as a layered manufacturing method involving HIP (hot isostatic pressing method) treatment or a three-dimensional layered manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2015-182419 may be appropriately adopted. Then, depending on which additive manufacturing method is adopted, for example, when heat treatment or HIP (hot isostatic pressing method) treatment is involved, attention should be paid to the heat treatment temperature. That is, this is to prevent the duplex structure from being transformed into a lamellar structure as much as possible. Incidentally, the heat treatment temperature referred to here is preferably 1050 ° C to 1150 ° C, and the heat treatment time at that time is preferably 1 to 3 hours. The reason is that if it is outside this temperature range and time range, regardless of the upper and lower limits, the duplex structure may be deformed into a lamellar structure as described above, and there is no elongation, that is, the ductility is less than 2%. Because. Regarding the lamination of the hard layer 2 and the soft layer 3, if the fact that they are laminated alternately is observed, the hard layer 2 and the soft layer 3 have a layered structure perpendicular to the lamination direction as shown in FIG. Don't worry about it.

Next, the molding angle of the titanium-aluminum alloy will be described with reference to FIGS. 2 to 4.

2 to 4 are schematic views showing a state in which rectangular pieces 4a, 4b and 4c are cut out from the titanium-aluminum alloy according to the present invention at each modeling angle. The "modeling angle" referred to in the present invention is the stacking direction of titanium and aluminum or a titanium-aluminum alloy powder (also in FIGS. 2 to 4, it is represented by an arrow A as in FIG. 1; hereinafter, simply "stacking direction". () And the longitudinal (major axis) direction of the rectangular piece (in FIGS. 2 to 4, they are similarly represented by the broken arrow E. Hereinafter, they are simply referred to as the "longitudinal (major axis) direction"). Refers to the angle θ formed by (see FIGS. 2 to 4 and FIGS. 5 to 8 described later). As for the titanium-aluminum alloy before cutting out the rectangular pieces 4a, 4b and 4c, the one in which the hard layer 2 and the soft layer 3 shown in FIG. 1 have a layered structure perpendicular to the laminating direction is used. To do.

First, FIG. 2 is a schematic view showing a state of cutting out when the stacking direction and the longitudinal (major axis) direction of the rectangular pieces are made to coincide (or parallel), that is, when the modeling angle θ = 0 °. .. However, the aspect in FIG. 2 is sufficiently manufactured by the conventional laminated modeling technique. That is, the layers of the hard layer 2 and the soft layer 3 are laminated perpendicularly to the stacking direction. In this case, as shown in FIG. 2A, the rectangular piece 4a surrounded by the broken line is cut out in the laminated titanium-aluminum alloy 1. By the way, when manufacturing a structure such as a turbine blade or an engine valve made of a titanium-aluminum alloy by a conventional laminated structure method or a three-dimensional lamination (modeling) method, as shown in FIG. 2, the titanium-aluminum alloy powder is used. The stacking direction and the longitudinal direction of the rectangular piece (in this case, the structure to be manufactured) referred to in the present invention (in this case, the molding direction of the structure to be manufactured). It is common to manufacture by matching (or paralleling). It should be noted that the rectangular piece 4a can be cut out by the conventional technique. Further, the size of the rectangular piece 4a can be changed as appropriate. Then, as shown in FIG. 2B, the rectangular piece 4a has a layered structure in which the hard layer 2 and the soft layer 3 are perpendicular to the stacking direction, which is the same as before cutting out.

Next, FIG. 3 shows the case where an angle (in the range of 0 ° to 90 °, excluding 0 ° and 90 °) is provided between the stacking direction and the longitudinal (major axis) direction of the rectangular piece 4b. That is, it is a schematic diagram which shows the state of cutting out when the modeling angle θ is provided. In this case, as shown in FIG. 3A, the rectangular piece 4b surrounded by the broken line is cut out in the laminated titanium-aluminum alloy 1. It should be noted that the rectangular piece 4b can be cut out by the conventional technique in the same manner as in the embodiment shown in FIG. Further, the size of the rectangular piece 4b can also be appropriately changed in the same manner as in the embodiment shown in FIG. Then, as shown in FIG. 3 (B), the rectangular piece 4b has a structure in which the hard layer 2 and the soft layer 3 are alternately laminated in the same manner as in the embodiment shown in FIG. 2 (B), but is hard. The layer 2 and the soft layer 3 are inclined and laminated with inclination angles θ ₁ and θ ₂ , respectively. By the way, both the inclination angles θ ₁ and θ ₂ are substantially the same as 90 ° −θ. The details of the modeling angle θ will be described later.

Next, FIG. 4 is a schematic view showing a state of cutting out when the stacking direction and the longitudinal (major axis) direction of the rectangular piece 4b are perpendicular to each other, that is, when the modeling angle θ is 90 °. In this case, as shown in FIG. 4A, the rectangular piece 4c surrounded by the broken line is cut out in the laminated titanium-aluminum alloy 1. It should be noted that the rectangular piece 4c can be cut out by the conventional technique in the same manner as in the embodiment shown in FIG. Further, the size of the rectangular piece 4c can also be appropriately changed in the same manner as in the embodiment shown in FIG. The rectangular piece 4c has a structure in which the hard layer 2 and the soft layer 3 are alternately inserted, or as shown in FIG. 3 (B), unlike the embodiment shown in FIGS. 2 (B) and 3 (B). Although not shown, only one of the hard layer 2 and the soft layer 3 is formed depending on the cutout portion. The details of the modeling angle θ will be described later.

Next, the modeling angle will be described. First, when the mode shown in FIG. 2, that is, the value of the modeling angle θ is 0 °, each strength such as tensile strength is not so different from the mode shown in FIG. 3, but is at room temperature (about 50 ° C or less). ) Has a tensile ductility (tensile ductility) similar to that of titanium-aluminum alloys manufactured by the prior art, that is, 1% or less, which does not meet the object of the present invention.

Next, when the mode shown in FIG. 4, that is, the value of the modeling angle θ is 90 °, each strength such as tensile strength becomes stronger or weaker. The reason is related to the balance between the hard layer 2 and the soft layer 3. Further, the ductility (tensile ductility) at room temperature (approximately 50 ° C. or lower) is somewhat better (for example, about 2%) than the aspect shown in FIG. 2, but is lower than the ductility of the titanium-aluminum alloy according to the present invention. Moreover, since the strength varies as described above, it does not meet the object of the present invention.

In view of this, it is considered that the mode shown in FIG. 3, that is, the modeling angle should be set within the range of 0 ° to 90 ° (however, 0 ° and 90 ° are excluded). Is done. The effect in this case will be described in detail later in the section of Examples. The modeling angle is preferably 40 ° to 60 °, more preferably 40 ° to 50 ° (45 ° ± 5 °). If the molding angle is less than 40 °, there is no elongation related to tensile ductility. Further, when the angle is larger than 60 °, the strength varies and the elongation related to tensile ductility does not increase so much. Incidentally, in the embodiment shown in FIG. 3, both the inclination angles θ ₁ and θ ₂ of the hard layer 2 and the soft layer 3 are substantially the same as 90 ° −θ, but the range is also the same. It is in the range of 0 ° to 90 °, which is the same as the modeling angle. However, the ductility at room temperature (approximately 50 ° C. or lower) is higher than that shown in FIGS. 2 and 4. By the way, the ductility is about 2 to 3.5%. It is desirable that the ductility is compatible with other strengths (for example, yield stress).

Although the rectangular piece has been described as an example of the test piece, the present invention is not limited to this, and the shape of the test piece of the titanium-aluminum alloy is not limited, and a structure such as a turbine blade may be used. I do not care. Further, although the rectangular piece is described as "cutting out" in this specification, if the expression "cutting out" is not appropriate depending on the shape of the test piece and the method of laminated molding adopted, for example, "(titanium-aluminum alloy powder)". () Laminate (laminate and model so that the angle between the longitudinal direction and the stacking direction of the structure is θ) ”and so on.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various aspects are adopted within the scope of the matters described in the specification, claims and / or drawings of the present application. Needless to say.

In order to support the matters described in the above-described embodiment, a titanium-aluminum test piece according to the present invention was prepared, and an effect test was conducted on the test piece. The preparation of the test piece and the effect test are merely examples, and are not limited to those described below, but are within the scope of the matters described in the specification, claims and / or drawings of the present application. Needless to say, it takes various aspects.

Further, if necessary, the description may be made with reference to the drawings of FIGS. 1 to 4.

(1) Preparation of Test Pieces According to Comparative Examples 1 and 2 and Example 1 First, as the test pieces used in (2) and (3) described later, a titanium-aluminum alloy round bar (hereinafter referred to as "round bar test piece"). Alternatively, the molding angle is 0 ° (hereinafter referred to as “Comparative Example 1”) and 45 ° (hereinafter referred to as “Comparative Example 1”) by the electron beam three-dimensional laminated molding method (3D-EBM method). A total of 3 pieces were prepared at "Example 1") and 90 ° (hereinafter referred to as "Comparative Example 2"). As shown in FIG. 5, the modeling angle referred to here corresponds to the stacking direction of the titanium-aluminum alloy (corresponding to the arrow A in FIGS. 2 to 4; and corresponds to “Building direction” in FIG. ) And the long axis direction of the round bar test piece according to each example (corresponding to the broken line arrow E in FIGS. 2 to 4; and corresponding to the “Cylinder direction” in FIG. 5). Say the angle to be made. Incidentally, the composition ratio of each test piece according to Example 1, Comparative Examples 1 and 2 was Ti-48Al-2Cr-2Nb (at% (atomic composition percentage)), respectively. Needless to say, this composition ratio is merely an example, and can be appropriately changed as long as it is within the range described in the above-described embodiment and claims. Further, regarding the cutting out of each test piece, the description is omitted because it does not affect the basis of the titanium-aluminum alloy of the present invention, that is, the constitution and the surface condition, and any known method is sufficient.

Further, the test piece was produced by the 3D-EBM method, but the present invention is not limited to this, and the test piece can be appropriately produced by other additive manufacturing methods if the modeling angle is appropriately set. Further, although the shape of the test piece is a round bar in this embodiment, the shape is not limited to that shape, and a structure such as a turbine blade may be used in some cases.

(2) Surface Observation of Each Test Piece Next, the surface of each of the test pieces according to Example 1, Comparative Examples 1 and 2 was observed with an optical microscope. An optical microscope image of the surface of each test piece is shown in FIG.

Each test piece had a two-layer structure consisting of a hard layer and a soft layer. Here, the thickness of the duplex layer (DP layer, corresponding to the hard layer) was about 55 μm in Example 1, about 57 μm in Comparative Example 1, and about 54 μm in Comparative Example 2. The thickness of the soft layer (equal axis γ structure) was about 33 μm in Example 1, about 36 μm in Comparative Example 1, and about 33 μm in Comparative Example 2. The ratio of the hard layer to the soft layer, that is, the value of (hard layer / soft layer) was 1.7 in Example 1, 1.6 in Comparative Example 1, and 1.6 in Comparative Example 2.

(3) Dependence of tensile ductility and strength (yield stress) at room temperature on plasticity angle Next, each test piece according to Example 1 and Comparative Examples 1 and 2 was tested for tensile ductility at room temperature (20 to 25 ° C.). did. Regarding the test conditions, a tensile test piece having a gauge portion of 1.5 mm in width × 1 thickness × 5 mm in length was cut out from each of the test pieces according to Example 1 and Comparative Examples 1 and 2 and in the atmosphere (about 1). Atmospheric pressure = 1.013 × 10 ⁵ Pa), and the strain rate was measured as 1.7 × 10 ^-4 s ^-1 .

A graph showing the relationship between the molding angle and ductility (%) of each test piece is shown in FIG. The elongation (ductility) in Comparative Example 1 was less than 1%. The elongation in Comparative Example 2 was about 2%. On the other hand, the growth in Example 1 was about 3%. From this, as described in the section of the above-described embodiment, the modeling angle is within the range of 0 ° to 90 ° (excluding 0 ° and 90 °), and the modeling angle is a certain angle. It has been demonstrated that it is better to provide (40 ° to 60 ° is desirable, more preferably 40 ° to 50 ° (45 ° ± 5 °)).

After this tensile ductility test, the surface of the test piece according to Example 1 was further photographed with an optical microscope. The figure is shown as FIG. 8 (A). It was found that some deformation occurred in the soft layer (equal axis γ tissue). Regarding this, when a load is applied in the long axis direction of the test piece, it is considered that the ductility is extended due to the concentration of shear deformation (see FIG. 8 (B)) as shown by the arrow on the soft layer. Is done.

In addition, the strength (yield stress) of each test piece according to Example 1 and Comparative Examples 1 and 2 was measured. FIG. 9 shows a graph showing the relationship between the modeling angle of each test piece and the yield stress (MPa). In this graph, the yield stress of Example 1 is slightly lower than that of Comparative Examples 1 and 2, but it does not mean that a substantial change is observed. In other words, it was found that the yield stress was substantially constant regardless of the modeling angle. However, in the titanium-aluminum alloy according to the present invention, the result suggests that both ductility and yield stress are established when the molding angle is provided as in Example 1 (modeling angle θ = 45 °). became.

(4) Preparation of Test Pieces According to Examples 2 and 3 Next, as the test pieces used in (5) and (6) described later, a titanium-aluminum alloy round bar (hereinafter referred to as "round bar test piece" or simply "test". Two types of "pieces" were produced by the electron beam three-dimensional laminated molding method (3D-EBM method) in the same manner as in (1) above. Here, of the two types of test pieces, in this embodiment, the one having a molding angle θ = 40 ° is referred to as “Example 2”, and the one having a molding angle θ = 60 ° is referred to as “Example 3”. By the way, since the modeling angle has already been explained in (1) above, the explanation is omitted. The composition ratio of each of the test pieces according to Examples 2 and 3 was Ti-48Al-2Cr-2Nb (at% (atomic composition percentage)). Needless to say, this composition ratio is merely an example, and can be appropriately changed as long as it is within the range described in the above-described embodiment and claims. Further, the cutting out of each test piece is described in the same manner as in (1) above because it does not particularly affect the basis of the titanium-aluminum alloy of the present invention, that is, the composition and surface conditions, and any known method is sufficient. Is omitted.

Further, as in (1) above, the test piece was produced by the 3D-EBM method, but the present invention is not limited to this, and the test piece can be appropriately produced by other additive manufacturing methods if the modeling angle is appropriately set. Further, although the shape of the test piece is a round bar in this embodiment, the shape is not limited to that shape, and a structure such as a turbine blade may be used in some cases.

(5) Surface Observation of Each Test Piece Next, the surface of each of the test pieces according to Examples 1, 2 and 3 was observed with a scanning electron microscope. A scanning electron microscope image of the surface of each test piece is shown in FIG.

Each test piece had a two-layer structure consisting of a hard layer and a soft layer. Here, the thickness of the duplex layer (DP layer, corresponding to the hard layer) was about 55 μm in Example 1, about 59 μm in Example 2, and about 60 μm in Example 3. The thickness of the soft layer (equal axis γ structure) was about 33 μm in Example 1, about 33 μm in Example 2, and about 32 μm in Example 3. However, the thicknesses of the duplex layer and the soft layer of Example 1 were substantially the same as those in (2) above. The ratio of the hard layer to the soft layer, that is, the value of (hard layer / soft layer) was 1.7 in Example 1, 1.8 in Example 2, and 1.9 in Example 3.

(6) Dependence on modeling angle of tensile ductility at room temperature Next, the tensile ductility at room temperature (20 to 25 ° C.) was tested for each of the test pieces according to Examples 1, 2 and 3. Regarding the test conditions, a tensile test piece having a gauge portion of width 1.5 × thickness 1 × length 5 mm was cut out from each of the test pieces according to Examples 1, 2 and 3, and the strain rate was 1.7 ×. It was measured as 10 ^-4 s ^-1 .

A graph showing the relationship between the molding angle of each test piece and the ductility (%) is shown in FIG. The elongation (ductility) of both Examples 2 and 3 was about 2.5%. On the other hand, the growth in Example 1 was about 3%. From this, as described in the above embodiment and the above section (3), the modeling angle is within the range of 0 ° to 90 ° (however, 0 ° and 90 ° are excluded), and the modeling angle thereof. It was demonstrated that it is better to provide a certain angle (preferably 40 ° to 60 °, more preferably 40 ° to 50 ° (45 ° ± 5 °)). In Comparative Example 1 and Comparative Example 2 in FIG. 11, similarly to the above (2) and (3), the case where the modeling angle θ = 0 ° is Comparative Example 1, and the case where the modeling angle θ = 90 °. Is Comparative Example 2.

(7) Preparation of Test Pieces According to Examples 4 and 5 Next, as the test pieces used in (8) and (9) described later, a titanium-aluminum alloy round bar (hereinafter referred to as "round bar test piece" or simply "test". Two types of "pieces" were produced by the electron beam three-dimensional laminated molding method (3D-EBM method) in the same manner as in (1) and (4) above. Here, in both of the two types of test pieces, the molding angle θ = 45 ° and the scanning speed of the electron beam of the 3D printer according to the 3D-EBM method are increased, which is referred to as “Example 4”. Here, it is described that "the scanning speed of the electron beam of the 3D printer according to the 3D-EBM method has been increased" with respect to Example 4, but in this case, Comparative Examples 1 and 2 and Examples 1, 2, 3 and It is 1.25 times faster than the scanning speed of the 3D printer at the time of producing the test piece according to Example 5 described later (Note that Comparative Examples 1 and 2 and Examples 1, 2 and 3 described later, and Example 5 described later). The scanning speed of the 3D printer at the time of producing the test piece according to the above is the same). Further, the product subjected to heat treatment (1100 ° C., 2 hours) is referred to as "Example 5". By the way, since the modeling angle has already been explained in (1) above, the explanation is omitted. The composition ratio of each of the test pieces according to Examples 4 and 5 was Ti-48Al-2Cr-2Nb (at% (atomic composition percentage)). Needless to say, this composition ratio is merely an example, and can be appropriately changed as long as it is within the range described in the above-described embodiment and claims. In addition, regarding the cutting out of each test piece, since it does not particularly affect the basis of the titanium-aluminum alloy of the present invention, that is, the composition and the surface condition, any known method is sufficient, and thus (1) and (4) above. ) Similarly, the explanation is omitted.

Further, as in (1) and (4) above, the test piece was prepared by the 3D-EBM method, but the present invention is not limited to this, and the test piece can be appropriately produced by other additive manufacturing methods if the modeling angle is appropriately set. is there. Further, although the shape of the test piece is a round bar in this embodiment, the shape is not limited to that shape, and a structure such as a turbine blade may be used in some cases.

(8) Surface Observation of Each Test Piece Next, the surface of each of the test pieces according to Examples 1, 4 and 5 was observed with a scanning electron microscope. A scanning electron microscope image of the surface of each test piece is shown in FIG.

Each test piece had a two-layer structure consisting of a hard layer and a soft layer. Here, the thickness of the duplex layer (DP layer, corresponding to the hard layer) was about 55 μm in Example 1, about 66 μm in Example 4, and about 64 μm in Example 5. The thickness of the soft layer (equal axis γ structure) was about 33 μm in Example 1, about 29 μm in Example 4, and about 55 μm in Example 5. However, the thicknesses of the duplex layer and the soft layer of Example 1 were substantially the same as those of (2) and (5) above. The ratio of the hard layer to the soft layer, that is, the value of (hard layer / soft layer) was 1.7 in Example 1, 2.3 in Example 4, and 1.2 in Example 5.

(9) Dependence of tensile ductility at room temperature on process conditions Next, the tensile ductility at room temperature (20 to 25 ° C.) was tested for each of the test pieces according to Examples 1, 4 and 5. Regarding the test conditions, a tensile test piece having a gauge portion of 1.5 width × thickness 1 × length 5 mm was cut out from each of the test pieces according to Examples 1, 4 and 5, and the strain rate was 1.7 ×. It was measured as 10 ^-4 s ^-1 .

A graph showing the ductility (%) of each test piece is shown as FIG. Example 4 was about 2.2%. Moreover, in Example 5, it was about 2%. On the other hand, the elongation (ductility) in Example 1 was about 3%. From this, when producing the titanium-aluminum alloy according to the present invention, the duplex layer is formed by changing the parameters of the 3D printer or the like used in the production (for example, the scanning speed of the 3D printer) or by performing heat treatment. The results suggest that it is possible to control the thickness and elongation of the soft layer.

By using the titanium-aluminum alloy of the present invention, it is expected to manufacture low-pressure turbine blades of aircraft, rotors of turbochargers such as automobiles, and engine valves of racing vehicles (for example, F1 machines).

1 Titanium-aluminum alloy 2 Hard layer 3 Soft layer 4a, 4b, 4c (titanium-aluminum alloy) rectangular piece

Claims (3)

In titanium-aluminum alloys
The titanium-aluminum alloy is composed of a hard layer having a duplex structure and a soft layer having γ single-phase equiaxed grains.
The hard layer and the soft layer has a laminated structure alternately, and shaping angle, Ri 40 ° to 60 ° der, and the titanium - room temperature ductility of the aluminum alloy with 2 to 3.5% titanium wherein there - aluminum alloy. The titanium-aluminum alloy according to claim 1, wherein the hard layer has a size of 1.1 to 3 times that of the soft layer. The titanium-aluminum alloy according to claim 1 or 2 , wherein the composition concentration of aluminum is 45 to 49 at%.