JPH08109454A - High strength metallic material and its production - Google Patents

Abstract

PURPOSE: To impart excellent mechanical properties and toughness to a metallic material by subjecting an amorphous alloy to heat treatment thereby obtaining a fine structure having grain size of a nano-unit. CONSTITUTION: At first, an amorphous alloy contg. any of Al, Mg and Ni and contg. the elements to be added selected from rare earths including Y and Mm, Ni, Fe, Co, Cu, Sn, Zn, Si and B is obtd. Next, it is subjected to primary heat treatment at a temp. of T1 to T2 +10K to T2 , i.e., the precipitating temp. of supersaturated solid solution contg. the elements of the alloy to be added and T2 , i.e., the temp. at which the residual amorphous phase after the precipitation of Cp is decomposed and precipitated into a metallic phase C1 and intermetallic compounds C2 using the main element as a base to largely precipitate Cp having grain size of several tens nm or below into the amorphous phase and simultaneously to form the precipitated embryos of C1 and C2 in the residual amorphous phase. After that, as the secondary heat treatment, it is rapidly heated to a temp. of >=T2 to decompose the residual amorphous phase into C1 and C2 having grain size of several tens nm, which is thereafter heated to a temp. higher than T2 to grow each precipited phase to <=100nm, and stabilization is executed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a metal material having excellent mechanical strength and toughness and a method for producing the same.

[0002]

2. Description of the Related Art The present inventors have found that Al, which has excellent strength and corrosion resistance,
Amorphous amorphous alloys and Mg-based amorphous alloys have been invented and disclosed in JP-A-64-47831 and JP-A-3-10041, respectively. The alloys described in these publications are aimed at an amorphous single phase. After that, the inventors invented that the strength and toughness can be improved by dispersing the crystal phase of a fine supersaturated solid solution containing the main element in an amorphous state, and filed a patent application as Japanese Patent Laid-Open No. 260037/1993. A similar invention was made in a Ni-based amorphous alloy,
A patent application was filed as Japanese Patent Laid-Open No. 5-70303. Further, it was found that when an amorphous alloy is heated to precipitate a supersaturated solid solution composed of a main element, it exhibits great ductility, and a patent for its production method was filed as Japanese Patent Laid-Open No. Hei 5-345961.
Furthermore, it was found that the supersaturated solid solution precipitated in the amorphous phase is a complete crystal, and the strength and toughness are remarkably improved,
The application was filed as JP-A-6-41703.

[0003]

[Patent Document 1] Japanese Patent Laid-Open No. 6-41703
The alloy described in the publication describes an alloy in which a supersaturated solid solution of 100 nm or less is uniformly precipitated and dispersed in an amorphous phase.
The present inventors have identified the residual amorphous phase described in the patent as:
As a result of further research to convert to a more stable crystalline phase, a metal phase composed of the main element,
It was discovered that a nanocrystal alloy in which all phases such as intermetallic compounds are composed of fine crystal grains of 100 nm or less can be formed, and the present invention has been completed.

[0004]

According to the present invention, an alloy obtained by heat-treating an alloy having a composition forming an amorphous alloy composed of a main element and an additive element is an additive element having the main element as a matrix. An alloy structure containing a supersaturated solid solution (C _p phase) containing, a metal phase (C ₁ phase) based on the main element, and an intermetallic compound (C ₂ phase), and the grain size of each phase is 100 nm or less. It is a high strength metal material. The alloy applied to the present invention forms an amorphous phase and is heat-treated at a relatively low temperature in the crystallization process, so that the amorphous phase has a particle size of several nm to several nm. Fine particles containing an additive element in a supersaturated state are precipitated and dispersed in a 10 nm crystal, and the amorphous phase remaining at a higher temperature is further separated into Cp phase and C ₂ phase.
It is limited to those that have a two-step transformation process that decomposes and precipitates into phases. Also, the Cp phase is preferably a perfect crystal. A perfect crystal is a supersaturated solid solution that is free of defects such as strain and dislocation.

One of such alloys is Al whose main element is 85-85.
99.8 atom%, the first additive element is at least one kind of rare earth elements including Y and Mm, and is 0.1 to 5 atom%, and the second additive element is Ni, Fe, Co, Cu. It is an alloy in which the concentration of at least one selected element is 0.1 to 12 atomic%, and the concentration of the first additive element is not more than the concentration of the second additive element. In one of the other alloys, the main element is M
80 to 90 atomic% in g, and the first additive element is Y, M
It is an alloy in which the rare earth element containing m is 0.1 to 5 atomic% and the second additive element is 8 to 15 atomic% of at least one element selected from Cu, Ni, Sn and Zn. Further, it is an alloy in which the main element is Ni at 79 to 89 atom%, the first additive element is Si at 5 to 14 atom%, and the second additive element is B at 6 to 15 atom%. The rest of the alloys have a main element of Ni of 74 to 88.5 at.
The additional element of Si is 5 to 14 atomic%, the second additional element is B of 6 to 15 atomic%, and the third additional element is Fe and M.
It is an alloy containing at least one element selected from n, Ti, Zr, Al, V, Mo and Nb and having an amount of 0.5 to 5 atom%.

The method for producing the alloy according to the present invention is as follows. That is, an oversaturated solid solution which is an alloy composed of a main element and another additive element and which forms an amorphous alloy, and which contains the additive element as the main element in the amorphous phase at a certain temperature (T ₁ ). (C _p ) is decomposed and precipitated, and at a temperature (T ₂ ) higher than T ₁ , the residual amorphous phase is decomposed and precipitated into a metal phase (C ₁ ) based on the main element and an intermetallic compound (C ₂ ). The alloy having the above property is subjected to a first-stage heat treatment at a temperature higher than T _{1 and} lower than T ₂ + 10K to obtain a grain size of several nm to several tens nm including an additive element based on the main element in an amorphous state. Of C _p is uniformly dispersed and at the same time, sprouting for decomposing into C ₁ and C ₂ in the residual amorphous phase is uniformly prepared and then rapidly heated to a temperature higher than T ₂ to remove residual non-phase. By decomposing and precipitating the crystalline phase into C ₁ and C ₂ which are composed of constituent elements and have a particle size of several nm to several tens nm respectively It is a method for producing a high-strength metal material, which obtains a high-strength metal material having a mixed structure of at least three phases. In addition, in order to thermally stabilize each precipitated phase, a heat treatment is performed at a temperature higher than the second stage heat treatment temperature, and finally each precipitated phase grows to a grain size of 100 nm or less. The first step of the method of the present invention is T ₁ or more and T ₂ +10.
By heat-treating at a temperature lower than K, a large amount of the C _p phase based on the main element having a grain size of several nm to several tens nm is uniformly precipitated in the amorphous material, and at the same time, the residual amorphous phase is further increased. It is to form and prepare the germination that becomes the nucleus for decomposing into C _p phase and C ₂ phase. In the second step, the alloy that has undergone the first step is kept at a temperature of T ₂ or higher, and the residual amorphous phase is decomposed with the sprouting generated in the first step as a nucleus.
Ideally, crystals are generated by the number of sprouting generated in the first step, and a very fine (several nm or less) structure is generated.

[0007] Since the amorphous phase to discharge the solute from C _p phase during the precipitation of C _p phase, the residual amorphous phase is increased solute concentration, to raise the decomposition temperature, the more stable sprouting In order to form a large number, the heat treatment in the first step is performed at the temperature T ₂
It is desirable to carry out at a temperature lower than the vicinity. Normally (T ₂ −
70 K) to (T ₂ +10 K) and a holding time of 15 seconds to 30 minutes. Especially in the case of Al alloy (T ₂
The holding time is preferably in the range of −30 K) to (T ₂ +5 K) for 1 to 30 minutes. As is well known, the decomposition process of the amorphous phase affects the particle size and the number of particles at which temperature and time are deposited. When treated at a too low temperature, the number of sprouts is large, but it takes a long time to obtain stable sprouts, which is not economical. Heat treatment at a temperature far exceeding T ₂ + 10K is stable, but the number of sprouting is reduced, and the crystal grain size during the second step heat treatment is coarsened. Further, in order to precipitate and disperse the supersaturated solid solution in the amorphous phase, it is also possible to control the cooling rate relatively slowly when the alloy liquid is rapidly cooled to become amorphous. Is sometimes used only to prepare sprouts for the decomposition of residual amorphous phase. Further, the heat treatment of the first step can be divided into a step of precipitating only Cp based on the main element and a step of preparing sprouts of residual amorphous phase decomposition. The point is to form a uniform nucleus.
FIG. 1 shows a schematic diagram of the structure after the first step heat treatment.

In the second step heat treatment, it is desirable to raise the temperature from the first step heat treatment temperature as quickly as possible. Usually, the temperature is raised in the range of 1 K / sec to 30 K / sec. The heat treatment temperature of the second step is close to the temperature at which the exothermic decomposition of the residual amorphous phase in the differential thermal analysis performed on the amorphous alloy at a temperature rising rate of 20 K / min ends. Usually T ₂ + (2
The range is from 0 to 120K). Hold time is 15 seconds to 30
The range of minutes is preferred. Especially in the case of Al alloy, T ₂ + (2
The range of 0 to 120K) and the retention time of 1 to 30 minutes are preferable. The reason for limiting the rate of temperature increase is to effectively use the germination of the first step and suppress undesired coarse crystal growth and generation, and the reason for limiting the temperature and time is also the same. This series of heat treatments suppresses the generation and growth of large crystals, causes proper fusion, coalescence, and aggregation of crystal grains, and discharges the solute of supersaturated solid solution while maintaining quasi-equilibrium (while maintaining the para-equilibrium effect). As a result, the chemical potential for crystal grain growth can be reduced, and a metal material can be obtained in which all the phases have a structure with a grain size of 100 nm or less. A schematic diagram of the structure after the second step heat treatment is shown in FIG.

Further, in order to manufacture the alloy of the present invention, it is necessary to complete a series of steps in a short time. Therefore, rapid heating and high speed processing are required. For rapid heating, direct heating to the alloy, infrared light converging heating, etc., and for high speed processing, high speed extrusion, high speed forging, etc. are suitable. However, these methods are not limited as long as this purpose can be achieved. Also, for the same purpose, a series of steps are combined. As an example,
Since the alloy is in the softened state at the heat treatment temperature of the second step, there is a case where the quenching alloy (powder, ribbon, wire, etc.) is solidified and molded simultaneously with the heat treatment. Although the crystal grains become slightly larger, it is also effective to perform heat treatment at a temperature higher than the heat treatment condition of the second step and a long holding time in order to maintain stability at high temperature for a long period of time. A schematic diagram of the structure after this heat treatment is shown in FIG. The amorphous alloy used in the present invention is an alloy that exhibits at least two exothermic peaks by differential scanning calorimetry (DSC). T ₂ is the temperature at which the non-equilibrium phase transforms (specifically, the crystallization temperature), and T ₁ is the temperature at which an exothermic reaction occurs on the lower temperature side than T ₂ .

[0010]

【Example】

Example 1 A _master alloy having a composition of Al _88.5 Ni ₈ Mm _3.5 was melted in an arc melting furnace, and a ribbon (thickness: 2) was formed by a commonly used single roll type liquid quenching device (melt spinning device).
0 μm, width: 1.5 mm) was produced. At that time, the roll is made of copper having a diameter of 200 mm, the rotation speed is 4000 rpm, and the atmosphere is Ar of 10 ⁻³ Torr or less. The produced ribbon was subjected to structural analysis by a usual X-ray diffraction method (diffractometer) and decomposition temperature of the quenched layer was measured by a differential scanning calorimetry. As a result of X-ray diffraction of the ribbon, the diffraction pattern showed only halo peculiar to the amorphous phase, and the ribbon was an amorphous single phase. This ribbon is 20K per minute by differential scanning calorimetry
The analysis was performed at the temperature rising rate of. FIG. 4 shows the results. As shown in the figure, there is a first peak rising at 400 K (T ₁ ) and a second peak rising at 570 K (T ₂ ). X
As a result of line diffraction, the first peak is from amorphous phase to Al (FCC)
Corresponds to a transformation in which the residual amorphous phase is decomposed and precipitated, and the second peak is a transformation in which the residual amorphous phase corresponds to the decomposition accompanied by the precipitation of the intermetallic compound. This amorphous alloy is sandwiched between two steel blocks held at a temperature of 545K and subjected to a first step heat treatment for 3 minutes, and a second block is also held for 2 minutes at a temperature of 620K.
It can be seen that, when the heat treatment of the step is performed, both the Al matrix and the intermetallic compound have crystal grains of 30 to 80 nm. The electron micrograph is shown in FIG. The mechanical properties of this alloy after each step treatment were measured. Table 1 shows the results. As a result of the heat treatment in the second step, it can be seen that the elongation, which is particularly useful in practice, is improved.

[0011]

[Table 1]

Example 2 A Mg ₈₃ Zn ₁₂ Ce ₅ alloy was prepared in the same manner as in Example 1 to produce a ribbon composed of an amorphous phase. According to the differential scanning calorimetry, the precipitation temperature (T1) of the Mg (hcp) phase of this alloy is 358.
K, the decomposition temperature (T2) of the residual amorphous phase into the intermetallic compound and the Al phase was 480K. Therefore, the heat treatment of the first step is 430K for 40 seconds, and the heat treatment of the second step is 51 seconds.
It was performed at 0K for 15 seconds. As a result of the structure observation by TEM,
The alloy after the second step treatment had a crystal grain size in the range of 20 to 90 nm for both the Mg matrix phase and the intermetallic compound phase. Its mechanical properties are shown in Table 2.

[0013]

[Table 2]

Example 3 A Ni ₈₀ Si ₈ B ₁₂ alloy was produced in the same manner as in Example 1 to produce a ribbon composed of an amorphous phase. According to the differential scanning calorimetry, the precipitation temperature (T1) of the Ni (fcc) phase of this alloy is 648.
K, the decomposition temperature (T2) of the residual amorphous phase was 760K. Therefore, the heat treatment of the first step was performed at 690K for 3 minutes, and the heat treatment of the second step was performed at 820K for 2 minutes. As a result of the structure observation by TEM, the alloy after the second step treatment has both Ni matrix phase and intermetallic compound phase.
The crystal grain size was 0 to 60 nm. Its mechanical properties are shown in Table 3.

[0015]

[Table 3]

[0016]

According to the present invention, a nanocrystal alloy having a crystal grain size of 100 nm or less can be obtained. This alloy is expected to have a wide range of applications as a high strength material.

[Brief description of drawings]

FIG. 1 is a schematic view of a structure of an Al alloy of the present invention after a first step heat treatment.

FIG. 2 is a schematic view of the structure of the Al alloy of the present invention after the second step heat treatment.

FIG. 3 is a schematic view of the structure of the Al alloy of the present invention after heat treatment at a temperature higher than the second step.

FIG. 4 is a graph showing the results of differential scanning calorimetry of the ribbon obtained in the example.

FIG. 5 is an electron micrograph showing the metal structure of the material obtained in the example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C22C 45/04 Z C22F 1/04 A 1/06 1/10 A (72) Inventor Akihisa Inoue Miyagi 11-806 (72) Inventor, Junichi Eito, 110-1, Nachikita-ji, Izumi-ku, Sendai-shi, Miyagi Prefecture

Claims (11)

[Claims] 1. An alloy obtained by heat-treating an alloy having a composition that forms an amorphous alloy composed of a main element and an additive element is a supersaturated solid solution (C _p phase) containing the additive element with the main element as a matrix. ), An alloy structure containing a metal phase (C ₁ phase) and an intermetallic compound (C ₂ phase) based on the main element, and the grain size of each phase is 100 nm or less, high strength. Metal material. 2. The high-strength metallic material according to claim 1, wherein the C _p phase is a perfect crystal. 3. The main element is Al in an amount of 85 to 99.8 atomic%, and the first additional element is 0.1 to 5 atomic% in at least one kind of rare earth element containing Y and Mm. The additive element of at least 1 selected from Ni, Fe, Co and Cu
The high-strength metal material according to claim 1 or 2, wherein the seed element is 0.1 to 12 atomic% and the concentration of the first additive element is not more than the concentration of the second additive element. 4. A part of Al is Ti, Mn, Mo, Cr,
The high-strength metal material according to claim 3, wherein the high-strength metal material is substituted with at least one element selected from Zr, V, Nb, and Ta to a range of 0.2 to 3 atomic%. 5. The main element is Mg in an amount of 80 to 90 atomic%, the first additive element is at least one kind of rare earth elements including Y and Mm in an amount of 0.1 to 5 atomic%, and the second additive is added. The high-strength metal material according to claim 1 or 2, wherein the element is at least one element selected from Cu, Ni, Sn, and Zn and is 8 to 15 atom%. 6. The high-strength metal material according to claim 5, wherein a part of Mg is replaced by at least one element selected from Al, Si and Ca in a range of 1 to 5 atomic%. 7. The main element is Ni at 79 to 89 atomic%, the first additive element is Si at 5 to 14 atomic%, and the second additive element is B at 6 to 15 atomic%. The high-strength metal material according to claim 1 or 2. 8. The main element is Ni at 74 to 88.5 atomic%, and the first additive element is Si at 5 to 14 atomic%.
The second additive element is 6 to 15 atomic% of B, and the third additive element is Fe, Mn, Ti, Zr, Al, V, Mo, N.
The high-strength metal material according to claim 1 or 2, wherein the content of at least one element selected from b is 0.5 to 5 atom%. 9. An alloy which is composed of a main element and another additive element and which forms an amorphous alloy at a certain temperature (T
_{In 1} ), a supersaturated solid solution (C _p ) containing an additive element as a main element is decomposed and precipitated in the amorphous phase, and the residual amorphous phase is based on the main element at a temperature higher than T ₁ (T ₂ ). An alloy having a property of decomposing and precipitating into a metal phase (C ₁ ) and an intermetallic compound (C ₂ ) is subjected to a first-stage heat treatment at a temperature higher than T _{1 and} lower than T ₂ + 10K, and mainly in an amorphous state. A large amount of C _p having a particle diameter of several nm to several tens of nm including an additional element based on an element is uniformly dispersed, and at the same time, a sprout for decomposing into C ₁ and C ₂ in a residual amorphous phase is uniformly deposited. was prepared, thereafter T to a temperature higher than ₂ is rapidly heated, at least 3 by decomposition deposit on the residual C ₁ of each particle diameter of several nm~ tens nm consisting of constituent elements of the amorphous phase and C ₂ A method for producing a high-strength metallic material, characterized in that a high-strength metallic material having a mixed structure of phases or more is obtained. 10. The method according to claim 9, further comprising heat-treating each precipitation phase at a temperature higher than the heat treatment temperature of the second stage to thermally stabilize each precipitation phase, and finally each precipitation phase grows to a grain size of 100 nm or less. Manufacturing method of high strength metal material. 11. A rare earth element containing Y, Mm as a main element, which is one of Al, Mg, and Ni, and Ni,
Fe, Co, Cu, Ti, Mn, Mo, Cr, Zr,
The method for producing a high-strength metal material according to claim 9 or 10, which is selected from V, Nb, Ta, Sn, Zn, Al, Si, Ca, and B.