KR20130031961A - Amorphous matrix composites modified from titanium alloys and method of manufactruing the same - Google Patents

Abstract

The present invention was devised to solve the problems of the conventional amorphous alloy, and provides a new amorphous composite material having improved weak vulnerable room temperature tensile properties of the existing amorphous alloy while maintaining the high strength, hardness and corrosion resistance of the amorphous alloy, etc. It aims to do it.
The amorphous composite material according to the present invention for achieving the above object, Ti: 44 to 56 atomic%, Zr: 24 to 29 atomic%, Ni: 2 to 4 atomic%, Be: 10 to 15 atomic%, V: 4 It contains ~ 8 atomic%, Al: 1 to 3 atomic% and consists of the remaining unavoidable impurities, characterized in that it contains a part of the crystalline phase.

Description

Amorphous composite using titanium alloy and its manufacturing method {AMORPHOUS MATRIX COMPOSITES MODIFIED FROM TITANIUM ALLOYS AND METHOD OF MANUFACTRUING THE SAME}

The present invention relates to an amorphous composite material using a commercially available titanium alloy and a method for manufacturing the same. More specifically, by adding an additional alloying element to a commercially available amorphous titanium alloy, a crystalline resinous phase is formed in the amorphous alloy matrix, particularly at room temperature. The present invention relates to an amorphous composite material having excellent tensile properties and a method of manufacturing the same.

As the materials used in the modern industrial society are advanced in industries such as automobiles, aviation, heavy equipment, and electronics, the development of metal materials that exceed the limit characteristics of existing metal materials is absolutely required.

In general, the plastic deformation at room temperature of the amorphous alloy is concentrated in a highly localized shear band and shows little plastic region upon tension and compression. In addition, the local plastic deformation in one shear band is very large, and only a few shear bands work until fracture, leading to brittle fracture.

However, in an amorphous alloy composite material in which soft crystalline dendrite is in situ in an amorphous alloy matrix, multi-shear bands are formed by the presence of dendritic phases. It acts as a major deformation mechanism in non-existent amorphous alloys. In this regard, it has been reported that when the Zr-based amorphous alloy composite material including the soft crystalline resin phase is loaded, more shear bands are generated than the shear bands generated in the completely amorphous alloy, thereby improving ductility. Accordingly, many researchers have been investigating the introduction of crystal phases into amorphous bases in various ways to improve the room temperature elongation of amorphous alloys.

Despite these efforts, the amorphous composites developed to date show some plastic deformation under compressive stress, but most of them are vulnerable to plastic deformation under tensile stress. It is because it has only a few mm in size.

The present invention has been researched and developed in order to solve the problems of the conventional amorphous alloy described above, while maintaining the properties such as high strength, hardness and corrosion resistance of the amorphous alloy, the weak room temperature tension of the existing amorphous alloy or amorphous composite material It is an object to provide a new amorphous composite with improved properties.

In addition, another object of the present invention is to provide a method of manufacturing an amorphous composite material having predetermined room temperature tensile stretching characteristics by controlling the size and distribution of the crystal phase formed during the solidification process.

The present invention as a means for solving the above problems, Ti: 40 to 60 atomic%, Zr: 20 to 30 atomic%, Ni: 2 to 10 atomic%, Be: 10 to 20 atomic%, V: 1 to 10 atoms %, Al: An amorphous composite material containing 0 to 5 atomic%, consisting of the remaining unavoidable impurities, and containing a part of the crystalline phase.

In addition, the crystalline phase of the amorphous composite material is characterized by forming a body centered cubic (BCC).

In order to obtain an amorphous composite material having improved elongation, a crystal phase that easily deforms in response to external stress and deformation is required. However, Ti and Ti alloys can form a body-centered cubic structure (BCC) and a hexagonal dense structure (HCP) according to temperature and composition, and slips occur more easily than a hexagonal dense structure in the case of a body-centered cubic structure. Since it is effective for improving the elongation at stretch, in the present invention, the crystal phase structure is a body centered cubic structure.

In addition, the average particle diameter of the crystal phase is characterized in that 10㎛ ~ 100㎛, this relatively coarse crystal phase size is responsible for the initial deformation and in particular has the effect of suppressing the propagation of cracks (cracks) starting from the amorphous phase This is because it contributes to the improvement of the drawing tensile rate. If the average particle diameter is less than 10 µm, the effect of suppressing propagation of cracks is inferior, and if it exceeds 100 µm, it is difficult to take advantage of the advantages of the amorphous base material.

In addition, the volume fraction of the crystalline phase is characterized in that 50% to 85%, which is when the fraction of the crystalline phase is too low, the breakdown of amorphous dominates leading to the improvement of the tensile elongation is impossible, when the fraction of the crystalline phase is high This is because the intrinsic properties of the amorphous alloy are lost, and the volume fraction of the amorphous phase is more preferably at least 20% or more.

In addition, the crystal phase is characterized by being deformed by sliding deformation due to dislocations.

In addition, all of the amorphous composite material is characterized by a slight work hardening from the yield point to the Ultimate Tensile Strength (UTS), and then necking occurs, and then through the continuous work softening to breakage, which is generated in the composite material It is a feature that can be obtained by the fact that the crystalline phase has a role of effectively preventing crack propagation.

In addition, the amorphous composite material is characterized in that the tensile elongation at room temperature of 3% or more.

In addition, the tensile strength of the amorphous composite material is characterized in that 1.0 ~ 1.2GPa.

In addition, in the amorphous composite material, when containing 1 atomic% or more of Al, V is contained at 4 atomic% or more, and the content ratio of V / Al is characterized in that it is 2.75 or more. When Al, which is an α-Ti stabilizing element, is added, the content of V, which is a β-Ti stabilizing element, is 2.75 times or more higher than that of Al, so that the dendritic strength can be increased without forming an unstable β phase, thereby improving strength and elongation. Can be planned together.

In addition, the present invention as a means for solving the other problem of the present invention, (a) Ti: 40 to 60 atomic%, Zr: 20 to 30 atomic%, Ni: 2 to 10 atomic%, Be: 10 to 20 atoms Preparing a master alloy containing%, V: 1 to 10 atomic%, and Al: 0 to 5 atomic% and remaining inevitable impurities; (b) heat-treating the master alloy in a coexistence region of a liquid phase and a solid phase in a non-oxidizing atmosphere; And (c) cooling the heat-treated master alloy to prepare an amorphous composite material including coarse crystal phases.

In the present invention, the non-oxidizing atmosphere is an atmosphere for preventing the master alloy from being oxidized during the heat treatment, and includes a vacuum state higher than 10 ⁻³ torr, an inert gas atmosphere, a reducing gas atmosphere, and the like.

In the present invention, the reheating temperature, that is, the temperature of the step (b) is preferably maintained at 800 ~ 900 ℃, this temperature is a temperature range where the alloy composition and the liquid phase coexist, within a short time This is to allow the crystal phase to grow to a desired size, and then to amorphous the liquid material through the quenching process to form an amorphous composite material.

In addition, in the present invention, the cooling process is rapidly cooled at a cooling rate of 10 ⁴ ~ 10 ⁶ K / sec so that the molten liquid component can form an amorphous state. If the cooling rate is less than 10 ⁴ K / sec, it is difficult to amorphous the liquid phase and exceeding the cooling rate 10 ⁶ K / sec is because unnecessary cost rises.

Next, the reason why the alloy component is set as described above in the present invention will be described.

Ti 40 to 60 atoms %

Ti is a main component for forming a resin phase, and when it is less than 40 atomic%, it is difficult to form a dendrite together with V and Al added. When Ti exceeds 60 atomic%, the volume ratio of the amorphous base material is excessively reduced. The range of 60 atomic% is preferable, and 44-56 atomic% is more preferable.

Zr 20 ~ 30 atoms %

Zr is a major component that forms a resinous phase with Ti. If it is less than 20 atomic%, it is difficult to form an amorphous phase, and if it exceeds 30 atomic%, the volume fraction of the dendrite together with Ti, V, and Al is lowered. It is preferable to add in 30 atomic%, and 24 to 29 atomic% is more preferable.

Ni 2 ~ 10 atoms %

Ni is a major component constituting the amorphous phase together with Ti and Zr, and when it exceeds 10 atomic%, it hinders the formation of a resinous phase, and it is preferable to contain less than 10 atomic%, and when less than 2 atomic%, Ni inhibits the physical properties of the amorphous phase. Therefore, it is preferable to contain in 2 atomic% or more, and 2-4 atomic% is more preferable.

Be 10 to 20 atoms %

Be is a component that improves the amorphous forming ability, when the addition of less than 10 atomic%, the amorphous base material itself is difficult to form, and when added in excess of 20 atomic%, similarly inhibits the amorphous forming ability, 10 to 20 atomic% Preferably, 10-15 atomic% is more preferable.

V: 1 ~ 10 atoms %

V is a Group 5 element and is dissolved in the β phase in the Ti alloy and acts as a β phase stabilizing element that enlarges the β phase region by lowering the (α + β) / α transformation point in the state diagram. The upper limit of V is higher than that of Ti-6Al-4V alloy. This is because by increasing the upper limit of V, it is possible to derive the desired β-phase property by affecting the elastic property of the β-phase. As for content of V, 4-8 atomic% is more preferable.

Al 0 to 5 atoms %

Al is a group III element, which is a solid solution in the α phase in the Ti alloy, and acts as an α phase stabilizing element which enlarges the α phase region by increasing the b / (α + β) transformation point. The content of Al is more preferably contained in 1 to 3 atomic% to improve ductility.

Inevitable impurities

The composite material according to the present invention may include impurities which are inevitably included in the manufacturing process, but the impurities other than the alloying elements should be maintained at 1 atomic% or less, preferably 0.1 atomic%, more preferably 0.01 It should be kept below atomic%.

The amorphous composite material and the manufacturing method thereof according to the present invention can be expected the following effects.

First, the amorphous composite material according to the present invention has excellent room temperature tensile strength, which is distinguished from conventional amorphous alloys, by controlling the crystal structure, the size and volume fraction of the crystal phase through alloy design and subsequent treatment (heat treatment or processing heat treatment). Its characteristics make it possible for industrial application to high functional products.

In addition, an in situ method can easily prepare a composite material in which a crystalline phase and an amorphous phase are mixed.

1a to 1c are photographs of the microstructure of the amorphous composite material prepared according to the embodiment of the present invention observed by scanning microscope.
2 is an X-ray diffraction analysis result of the amorphous composite material prepared according to the embodiment of the present invention.
3 is an EBSD result of an amorphous composite prepared according to an embodiment of the present invention.
4 is a stress-strain graph of a tensile test specimen prepared from an amorphous composite material prepared according to an embodiment of the present invention.
5 is a photograph of the tensile specimen after the tensile test of FIG.
Figure 6 shows the microstructure observed over time with a scanning electron microscope the state of deformation when a load is applied to the amorphous composite material prepared in accordance with an embodiment of the present invention.
7 is an EBSD result after the tensile test of the amorphous composite material prepared according to the embodiment of the present invention.

Hereinafter, an amorphous composite material according to a preferred embodiment of the present invention will be described in detail, but the present invention is not limited to the following examples. Therefore, it will be apparent to those skilled in the art that the present invention may be variously modified without departing from the technical spirit of the present invention.

Amorphous  Manufacture of Composites

We first use pure Ti (99.9%), pure Zr (99.9%), pure Ni (99.9%), pure Be (99.9%), pure V (99.9%) and pure Al (99.9%). A high-alloy argon (99.99%) gas atmosphere through an arc melter to prepare a master alloy having the composition shown in Table 1 below.

No. Subsidy (atomic%) Ti Zr Ni Be V Al A 51.7 28.3 3.21 11.79 5 - B 50 25 3 12 7.5 2.5 C 51.7 28.3 3 10 5 2

The prepared master alloy is heated at 800 ° C. to 900 ° C., which is a temperature at which a solid phase and a liquid phase coexist through an induction heater at a vacuum degree of about 10 ⁻⁴ Torr, and then maintained for 5 minutes to grow the crystal phase. After quenching, the crystalline and amorphous compounds are compounded in situ by allowing the remaining liquid component to become amorphous by quenching by quenching on the copper plate which is cooled by the cooling water flowing therein. Composite material was prepared. In this case, the ratio of the crystalline and amorphous phases of the composite material and the size of the dendritic phase may be controlled by controlling the solid / liquid coexistence ratio by controlling the heating temperature and time of the induction heater.

Microstructure and Component Analysis

The microstructure of the amorphous composite material thus prepared was analyzed using a scanning electron microscope (SEM), an X-ray diffractometer, and EBSD.

1A to 1C are SEM microstructure photographs of Ti-based amorphous composite materials A, B, and C alloys.

In the three alloys after the heat treatment and quenching, about 61 to 76% by volume of the crystal phases are uniformly distributed in the amorphous phase matrix. These crystal phases have a dendritic form that appears upon solidification, have a relatively smooth interface with the matrix, and have a spherical shape. In the alloys A to C, the volume fractions of the dendritic phase were 61%, 68%, and 76%, respectively. In the alloys A to C, the average size of the dendritic phase is 25.0 mm, 27.0 mm, and 24.1 mm, respectively.

Figure 2 shows the X-ray diffraction analysis of the alloys A ~ C.

As can be seen in FIG. 2, all three alloys show sharp crystalline peaks with an amorphous specific broad halo pattern. As a result of analyzing the crystal phase peaks, alloys A to C all have only peaks corresponding to the β phase of the bcc structure.

3 shows the results of EBSD analysis on alloys A-C.

In general, grains having an orientation difference of more than 15 ° are regarded as effective grains, and are displayed in different colors in the inverse pole figure (IPF) color map (FIG. 3). In FIG. 1, the size of the dendritic phase is about 25 mm, but it is connected with the same orientation so that the actual dendritic size is larger than this. The dendritic size measured from the EBSD IPF color map is 81 mm, 37 mm and 73 mm for alloys A, B and C, respectively. Alloys A, B and C are all composed of β phase.

Room temperature mechanical properties evaluation

4 shows room temperature tensile stress-strain curves of alloys A-C.

As confirmed in FIG. 4, alloy A exhibits a yield strength of 1.04 GPa and an elongation of 3.3%, alloy B exhibits a yield strength of 1.17 GPa and an elongation of 4.0%, and alloy C exhibits a yield strength of 1.03 GPa and 4.4. Elongation of% is shown. That is, all three alloys exhibit a high strength of 1 GPa or more and an elongation of about 3 to 4.5%, and thus have excellent tensile elongation characteristics compared to conventional amorphous alloys.

All alloys A to C showed some work hardening after the yield point to the maximum yield point (UTS), and then necking occurred, followed by steady work hardening and failure. Figure 5 is a low magnification photograph showing the specimen shape after the tensile test of the three alloys. The alloys A, B, and C all have necking and deformation is concentrated around the necking, and it can be confirmed that fracture occurs (FIG. 5), and the result is consistent with the tensile curve of FIG. 4.

FIG. 6 is a SEM photograph of a region in which deformation occurred near the wavefront of the C alloy after the tensile test, and was classified into early, middle, and late deformation according to the degree of deformation.

In Alloy C, a strain band is formed on the initial strain of the strain, and the strain band tends to be formed in the same direction in a predetermined region (Fig. 6 (a)). As the strain progresses, the strain band is connected to the strain band on the neighboring dendritic phase through an amorphous matrix (Fig. 6 (b)). If a lot of deformation occurs, one or two of the deformation bands are deepened and the deformation is concentrated, and cracking occurs in this deep deformation band, leading to fracture (Fig. 6 (c)).

On the other hand, the alloy of the present invention contains a coarse dendrite of 61 to 76% by volume in the amorphous matrix, there is no significant difference in the microstructure, but the yield strength and tensile strength of the alloy B is higher than the alloys A and C. As can be seen in FIG. 6, the deformation is first performed in the resin phase, and the alloy B including the higher hardness resin phase exhibits higher yield strength and tensile strength than the alloys A and C.

In the case of amorphous composites, deformation occurs first on resins that are easily deformed under low stress before reaching the yield strength of amorphous matrix. The resistance to such deformation is that alloy B is stronger than alloys A and C. In addition, in terms of elongation, alloys A, B, and C increased in order due to differences in the fractions of the dendritic phase. The dendritic fraction of alloy A is 61%, the dendritic fraction of alloy B is 68%, and the dendritic fraction of alloy C is 76%, increasing in the order of A, B, and C. Considered, the high volume fraction of the dendrite is responsible for the plastic deformation of the material. When the deformation band originated from the resin phase spreads to the amorphous phase and is deepened, the resistance to plastic deformation in the resin phase has a great effect on the elongation of the entire alloy, considering that rapid deformation occurs in the amorphous phase due to the characteristics of the amorphous phase. Judging.

However, in the transformation process, alloy C contains a different process from alloys A and B.

7 shows EBSD results after tensile strain of alloy C. FIG.

Most of the resin phase before deformation is composed of a β phase having a bcc crystal structure, but a phase transformation occurs in part of the β phase to the α phase (green) in the portion where the deformation has progressed (Fig. 7 (b)). These EBSD results indicate that the transformation of the β phase into the α phase (or α '' phase) occurs during the transformation.

Such phase transformations were not observed in alloys A and B. Referring to the EBSD results of FIG. 3, alloys A to C are all composed of β phases. However, when the EBSD results of FIG. 7 show that alloy C contains α phases in some dendritic phases after deformation, β phases are α in the resin phases. It can be said to be the result of transformation into a phase.

Comparing alloys A and C, which showed a difference in elongation at similar tensile strengths, alloys A and C were each added with the same amount of V, the stabilizing element V, to form a β phase. However, in the case of alloy C, Al, which is an α-phase stabilizing element, is added to form a β-phase which is more unstable than Alloy A. Therefore, it can be said that the β phase of alloy C is more unstable than the β phase of alloy A. As a result, the resin phase of alloy C is composed of β phase, but a small amount of α phase transforms into a structure coexisting with the β phase during deformation.

In some titanium alloys with low β phase stability, the β phase transforms into the α '' phase due to external load, and when such phase transformation occurs in the elastic section, the phase transformation between the β phase and the α '' phase occurs reversibly. Shape memory phenomenon may occur. Comparing the deformation behavior of two alloys having a resin phase composed of a stable β phase (alloy A) and an unstable β phase (alloy C), the alloys A and C both form strain bands in the resin phase and deformation occurs preferentially. In the case of an amorphous composite material having a hard amorphous base having a strength close to the theoretical strength due to the absence of dislocation and a crystal phase easily deformed under low stress by a deformation mechanism such as dislocation transfer, before the yield strength of the amorphous base is reached. Deformation occurs in the dendritic phase, and then the amorphous base is also deformed by linkage and propagation of the deformation originating in the dendritic phase. Alloys A and C faithfully follow the deformation behavior of these common composites. That is, the strain band is formed on the initial dendritic phase of deformation, and then the amorphous base is also deformed in the process of being connected to the modified band of neighboring dendritic phases.

However, since alloy C shows the transformation into the α phase during the deformation process, the formation of the deformation band in the resin phase may include a different process from that of the alloy A. However, in the case of the C alloy having a higher ductility than the alloy A, the deformation is preferentially performed in the resin phase. However, it is more resistant to deformation than alloy A. This can be said that in addition to the deformation by the high volume fraction of the dendritic phase described above, the result of transforming the organic phase transformation of some β phase to the α phase.

In general, α-Ti alloys having a low stacking fault energy are known to generate twins more during deformation than β-Ti alloys having a high stacking fault energy. Therefore, there is a possibility that twin phase deformation occurs in the α phase of alloy C, but if the α phase that is better formed than the slip is surrounded by the β phase and has a specific orientation with the β phase, the β phase can play a role in suppressing formation of the twin. have. If it consists only of the α phase, the interface with grain boundaries or amorphous bases provides the nucleation sites of the twins, allowing twins to form under low stress. However, when the α phase is surrounded by the β phase, the β phase interferes with the nucleation of the twin in the α phase and formation of the twin is difficult, so that the twin was not actually observed.

In the deformation process of alloy C, the α phase newly generated by the phase transformation is hardly deformed. Therefore, twins should be formed in the α phase during the deformation process.

Similarly, alloy B contains Al, which is an α-phase stabilizing element, and thus has a possibility of strain organic phase transformation. However, since the content of V, which is a β-phase stabilizing element, is also high, it cannot be said that it is unstable β-phase enough to cause phase transformation to α-phase. No phase transformation was observed. Alloy B exhibited an increase in strength than alloys A and C due to a high hardness of the resin phase, and in terms of elongation, it was judged to exhibit an effect of increasing elongation according to the fraction of the ductile dendritic phase having a fracture delay effect.

Claims (14)

Ti: 40 to 60 atomic%, Zr: 20 to 30 atomic%, Ni: 2 to 10 atomic%, Be: 10 to 20 atomic%, V: 1 to 10 atomic%, Al: 0 to 5 atomic% An amorphous composite material, consisting of the remaining unavoidable impurities, comprising a part of a crystalline phase. The method of claim 1,
The content of Ti is 44 to 56 atomic%, the content of Zr is 24 to 29 atomic%, the content of Ni is 2 to 4 atomic%, the content of Be is 10 to 15 atomic%, and the content of V is 4 to Amorphous composite material, characterized in that 8 atomic%, Al content is 1-3 atomic%. The method of claim 1,
The amorphous phase material has a body-centered cubic structure (BCC). The method of claim 1,
An amorphous composite material, characterized in that the average particle diameter of the crystal phase is 10㎛ ~ 100㎛. The method of claim 1,
The amorphous composite material, characterized in that the volume fraction occupies 50% to 85% of the total composite material. The method of claim 1,
The amorphous composite material is an amorphous composite material, characterized in that the tensile elongation at room temperature or more. The method of claim 1,
An amorphous composite material, characterized in that the tensile strength of the amorphous composite material is 1.0GPa or more. The method of claim 1,
The amorphous composite material is an amorphous composite material, characterized in that when the load is applied, strain organic phase transformation due to unstable β phase occurs. The method of claim 2,
The amorphous composite material, characterized in that the content ratio of V / Al is 2.75 or more. The method of claim 1,
The amorphous composite material is an amorphous composite material, characterized in that it comprises a β-phase structure surrounding the α phase in the microstructure after applying a load. (a) Ti: 40 to 60 atomic%, Zr: 20 to 30 atomic%, Ni: 2 to 10 atomic%, Be: 10 to 20 atomic%, V: 1 to 10 atomic%, Al: 0 to 5 atomic% Preparing a mother alloy containing and consisting of the remaining unavoidable impurities;
(b) heat-treating the master alloy in a coexistence region of a liquid phase and a solid phase in a non-oxidizing atmosphere; And
(c) cooling the heat-treated master alloy to prepare an amorphous composite material including coarse crystal phases. The method of claim 11,
A non-oxidizing atmosphere is one of a vacuum state higher than 10 ^-3 torr, an inert gas atmosphere, or a reducing gas atmosphere. The method of claim 11,
Wherein the heat treatment in step (b) is performed at 800 to 900 ° C. The method of claim 11,
The cooling of the step (c), the manufacturing method of the amorphous composite material, characterized in that carried out at a cooling rate of 10 ⁴ ~ 10 ⁶ K / sec.

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