JP2009221579A - Magnesium alloy material and method for manufacturing the same - Google Patents

Abstract

An object of the present invention is to provide a magnesium alloy material excellent in high mechanical properties and a method for producing the same without using special production equipment and processes.
A magnesium alloy material is an Mg-Zn-RE alloy containing Zn as an essential component and at least one of Gd, Tb, and Tm as RE, and the balance being Mg and inevitable impurities. And at least one of the β phase, β ′ phase, and β1 phase in the alloy structure of the Mg—Zn—RE alloy (X phase = elongated precipitate: acicular precipitate or plate shape) And a long-period laminated structure.
[Selection] Figure 1

Description

  The present invention relates to a magnesium alloy material and a manufacturing method thereof, and more particularly to a magnesium alloy material having high mechanical strength and a manufacturing method thereof.

In general, magnesium alloy materials have the lowest density, light weight, and high strength among the alloys that have been put to practical use, so that they can be used for electrical housings, automobile wheels, undercarriage parts, engine parts, etc. Application to is progressing.
In particular, in parts related to automobiles, high mechanical properties are required. Therefore, as a magnesium alloy material to which elements such as Gd and Zn are added, a specific form of material is applied by a single roll method or a rapid solidification method. Manufacturing is performed (for example, Patent Document 1, Patent Document 2, Non-Patent Document 1).

  However, the above-described magnesium alloy material has a problem that, in a specific manufacturing method, high mechanical properties are obtained, but there is a problem that special equipment is required and productivity is low, and further, applicable members are limited. is there.

Therefore, conventionally, when producing a magnesium alloy material, it is practically useful to carry out plastic working (extrusion) from normal high-productivity melt casting without using special equipment or processes as in the above-mentioned patent document. Have been proposed (for example, Patent Document 3 and Patent Document 4). It is known that the magnesium alloy materials disclosed in Patent Documents 3 and 4 can obtain high mechanical properties.
Japanese Patent Application Laid-Open No. 06-041701 JP 2002-256370 A International Publication No. 2005/052204 Pamphlet International Publication No. 2005/052203 Pamphlet Outline of the 108th Annual Meeting of the Japan Institute of Light Metals (2005) P42-45

However, the conventional magnesium alloy material has room for improvement as shown below.
That is, the conventional magnesium alloy material has been required to further improve the strength in order to promote application to automobiles for the purpose of weight reduction.

  The present invention has been devised in view of the above problems, and an object thereof is to provide a magnesium alloy material excellent in high mechanical properties and a method for manufacturing the same without using special manufacturing equipment and processes.

  In order to solve the above problems, the present invention is configured as the following magnesium alloy material. That is, it is an Mg—Zn—RE-based alloy containing Zn as an essential component and at least one of Gd, Tb, and Tm as RE, with the balance being Mg and inevitable impurities, and the Mg—Zn— The alloy structure of the RE alloy has a structure having at least one of a β phase, a β ′ phase, and a β1 phase and a long-period stacked structure.

By configuring in this way, the magnesium alloy has at least one of β phase, β ′ phase, β1 phase (hereinafter, also referred to as X phase) and a long-period laminated structure that precipitates and strengthens the material, Mechanical properties such as tensile strength, 0.2% proof stress, elongation (elongation rate) and the like are improved as a whole as compared with those having only the X phase or only the long-period laminated structure. The X phase is a needle-like precipitate or plate-like precipitate, and this needle-like precipitate or plate-like precipitate is Mg ₅ Gd or / and Mg ₇ Gd. This magnesium alloy forms a crystallized product of, for example, Mg ₃ Gd (Mg ₃ Zn ₃ Tb ₂ or Mg ₂₄ Tm ₅ ) by one or more of Gd, Tb, and Tm as RE, and the X phase. Combined with the acicular precipitates or plate-like precipitates (at least one of the β phase, β ′ phase, and β1 phase), the mechanical properties such as tensile strength, 0.2% proof stress, elongation, etc. To improve. In addition, it is preferable that the acicular precipitate or plate-shaped precipitate which is X phase is 7 micrometers or less.

In the magnesium alloy material, it is preferable that the Zn has a component range of 0.5 to 3 atomic%, and the RE has a component range of 1 to 5 atomic%.
With this configuration, the magnesium alloy material has an X-phase acicular precipitate or plate shape that improves the strength by setting the components of Zn and RE (Gd, Tb, Tm) within a predetermined range. Precipitates (at least one of a β phase, a β ′ phase, and a β1 phase) and a long-period stacked structure are likely to precipitate.

  Furthermore, in order to solve the said subject, the manufacturing method of a magnesium alloy material contains at least 1 or more of Zn as an essential component and Gd, Tb, and Tm as RE, and the remainder consists of Mg and an unavoidable impurity. A casting process for casting a Mg-Zn-RE alloy to form a cast material, a solution forming process for forming a solution of the cast material, and a first heat treatment process for performing heat treatment on the solution cast material under predetermined conditions And a second heat treatment step for performing heat treatment under predetermined conditions after the first heat treatment step, wherein the first heat treatment step is represented by y as a heat treatment temperature (° C.) and x as a heat treatment time (h). Then, -12 [ln (x)] + 375 <y <527 and 0.5 ≦ x <300 are satisfied. In the second heat treatment step, the heat treatment temperature (° C.) is y. , Heat treatment time (h) x When, at -18 [ln (x)] + 240 <y <-12 [ln (x)] + 375, and, it was decided to carry out a range of conditions shown in 2 <x <300.

In the method of manufacturing a magnesium alloy material according to such a procedure, the precipitates of Mg and RE are in a solution state by solution treatment, and the heat treatment conditions in the first heat treatment step and the second heat treatment step are within a predetermined range. By performing, the magnesium alloy material has an X-phase (at least one of β-phase, β′-phase, β1-phase) acicular precipitate or plate-like precipitate (Mg ₅ Gd or / and Mg ₇ Gd), a long By forming the periodic laminated structure, precipitation strengthening is performed, and mechanical properties such as tensile strength, 0.2% proof stress, and elongation are improved as a whole.

  In the method for producing a magnesium alloy material, an Mg—Zn—RE-based alloy containing Zn as an essential component and at least one of Gd, Tb, and Tm as RE and the balance being Mg and inevitable impurities. A casting process for forming a cast material by casting a solution, a solution forming process for forming a solution of the cast material, a first heat treatment process for heat-treating the solution cast material under a predetermined condition, and the first heat treatment process. The process further includes a second heat treatment step in which heat treatment is performed under predetermined conditions, and a plastic processing step in which plastic processing is performed on the cast material heat-treated in the second heat treatment step, and the first heat treatment step includes a heat treatment temperature (° C.). Where y is y and heat treatment time (h) is x, −12 [ln (x)] + 375 <y <527, and 0.5 ≦ x <300. The heat treatment process When the processing temperature (° C.) is y and the heat treatment time (h) is x, −18 [ln (x)] + 240 <y <−12 [ln (x)] + 375 and 2 <x <300 It was decided to carry out under the conditions in the range shown in. Further, in the method for producing the magnesium alloy material, the plastic working process is an extrusion process or a forging process.

The manufacturing method of the magnesium alloy material according to such a procedure is a state in which the precipitates of Mg and RE are in solution by the solution treatment, and the heat treatment conditions in the first heat treatment step and the second heat treatment step are within a predetermined range. By performing, an acicular precipitate or plate-like precipitate (Mg ₅ Gd or / and Mg ₇ Gd) that is an X phase (at least one of a β phase, a β ′ phase, and a β1 phase), a long-period stacked structure, Thus, the tensile strength, 0.2% proof stress, and elongation can be sufficiently improved with respect to plastic working.

  Furthermore, in the method for producing a magnesium alloy material, an Mg—Zn—RE-based alloy containing Zn as an essential component and at least one of Gd, Tb, and Tm as an RE, with the balance being Mg and inevitable impurities A casting process for forming a cast material by casting, a solution forming process for forming a solution of the cast material, a first heat treatment process for performing heat treatment on the solution cast material under predetermined conditions, and the first heat treatment process. A plastic processing step of performing plastic processing on the heat-treated cast material, and a second heat treatment step of performing heat treatment on the cast material subjected to the plastic processing under a predetermined condition, wherein the first heat treatment step includes a heat treatment temperature (° C.). Where y is y and heat treatment time (h) is x, −12 [ln (x)] + 375 <y <527, and 0.5 ≦ x <300. Heat treatment process is heat When the thermal temperature (° C.) is y and the heat treatment time (h) is x, −18 [ln (x)] + 240 <y <−12 [ln (x)] + 375 and 2 <x <300 It was decided to carry out under the conditions in the range shown in. Further, in the method for producing the magnesium alloy material, the plastic working process is an extrusion process or a forging process.

The manufacturing method of the magnesium alloy material according to such a procedure is a state in which the precipitates of Mg and RE are in solution by the solution treatment, and the heat treatment conditions in the first heat treatment step and the second heat treatment step are within a predetermined range. By performing, an acicular precipitate or plate-like precipitate (Mg ₅ Gd or / and Mg ₇ Gd) that is an X phase (at least one of a β phase, a β ′ phase, and a β1 phase), a long-period stacked structure, , Can be formed. Moreover, by forming the X phase, the tensile strength, 0.2% proof stress, and elongation can be sufficiently improved with respect to the plastic working after the first heat treatment step.

The magnesium alloy material and the manufacturing method thereof according to the present invention have the following excellent effects.
The magnesium alloy material includes an X phase (at least one of β phase, β ′ phase, β1 phase) which is a needle-like precipitate or a plate-like precipitate (Mg ₅ Gd or / and Mg ₇ Gd), and a long-period laminated structure. Therefore, mechanical properties such as tensile strength, elongation, and 0.2% proof stress with respect to a predetermined elongation rate are generally compared with those having only an X phase or a long-period laminated structure. Can be improved.

In the manufacturing method of the magnesium alloy material, since the heat treatment conditions are performed within a predetermined range after the solution treatment, the manufactured magnesium alloy material is acicular precipitate or plate-like precipitate (Mg ₅ Gd or / And Mg ₇ Gd) and an X phase (at least one of a β phase, a β ′ phase, and a β1 phase) and a long-period laminate structure, and have a tensile strength, elongation, and a predetermined elongation rate. Mechanical properties such as 0.2% proof stress are improved as a whole (compared to those having only the X phase or the long-period laminated structure) as compared with the conventional one. And such a magnesium alloy material can be efficiently manufactured by a general manufacturing facility or process.

  Further, when extrusion (plastic) processing is performed, mechanical properties that are not normally achieved can be obtained by having an X phase or a long-period laminated structure in the structure. Therefore, the magnesium alloy material can be used, for example, even in parts having severe mechanical properties such as automobile parts, particularly pistons.

The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1A is a TEM photograph showing a state in which at least one of a β phase, a β ′ phase, and a β1 phase and a long-period laminated structure appear in a metal structure of a magnesium alloy material. 1 (b) is a TEM photograph showing the appearance of a GP band appearing in the metal structure of the magnesium alloy material, and FIG. 2 is at least one of β phase, β ′ phase, and β1 phase in the metal structure of the magnesium alloy material. One or more and is a TEM photograph showing the long period stacking ordered structure, and crystallized substances of Mg 3 _Gd, the state has appeared. 3 shows a metal structure of the magnesium alloy material, and a TEM photograph showing a state in which a β ′ phase (elongated precipitate) appears. FIG. 4 shows a metal structure of the magnesium alloy material. FIG. 5 shows the metal structure of the magnesium alloy material, and shows the state in which the β phase (long precipitate) appears. It is a TEM photograph shown.

The magnesium alloy material 1 is an Mg—Zn—RE-based alloy containing Zn as an essential component and at least one of Gd, Tb, and Tm among RE (rare earth), the balance being Mg and inevitable impurities. Explained here as an example containing Gd. As shown in FIGS. 1 (a) and 2, the magnesium alloy material 1 has an X phase (β) that is a needle-like precipitate or a plate-like precipitate (Mg ₅ Gd or / and Mg ₇ Gd) in the alloy structure. Phase, at least one of β ′ phase and β1 phase) (hereinafter, referred to as long precipitate 2 for convenience) and a long-period stacked structure (LPSO) 3.

In addition, as shown in FIG. 2, the magnesium alloy material 1 in the case where RE is Gd as an Mg—Zn—RE based alloy has a long shape that is infinitely shown as white fine needles or fine plates. It is the precipitate 2 (acicular precipitate or plate-like precipitate), and the spot-like portion (larger than the needle-like precipitate or plate-like precipitate) that is dripped white is a crystallized product of Mg ₃ Gd, It is mixed and precipitated in the magnesium alloy material 1. Further, here, the magnesium alloy material 1, the elongate precipitate 2, and crystallized substances of MG 3 _Gd, the long period stacking ordered structure 3, it can be seen that a structure comprising a. In addition, as shown in FIGS. 1A and 1B, a GP band may be deposited. The GP band is a precursor state of precipitates such as the long precipitate 2. In addition, although the crystallized product of Mg ₃ Gd of the magnesium alloy material is solid-solutioned (solution-ized) by a solution treatment described later, it can be inferred that when the amount of addition is large, it appears as a supersaturated solid solution during heat treatment. Further, by this solid solution and heat treatment, long precipitates 2 (acicular precipitates or plate-like precipitates) and long-period laminated structure 3 are formed.

[(At least one of β phase, β ′ phase, β1 phase) = (acicular precipitate or plate precipitate) = (Mg ₅ Gd or / and Mg ₇ Gd)]
In the magnesium alloy material, at least one of the β phase, β ′ phase, and β1 phase is X-phase (X phase = acicular precipitate or plate-like precipitate (long precipitate 2)). It is a precipitate which precipitates under the temperature conditions of The appearance of this X phase improves the mechanical strength (tensile strength, elongation, 0.2% yield strength). In this X phase, if the long precipitate 2 is in the form of fine fine needles or plates and is too small, it does not contribute to the improvement of the strength. Leading to a decline. Therefore, the long precipitate 2 preferably has a size (length) in the range of 0.1 to 20 μm, more preferably in the range of 0.2 to 10 μm, and 0 More preferably, it is in the range of 3 to 7 μm. In addition, the elongate precipitate 2 is in a state where the aspect ratio is longer than 2: 1.

Further, as shown in FIG. 3 to FIG. 5, it can be seen that the long precipitate 2 changes the state of the phase appearing depending on the temperature condition and temperature time from the β ′ phase to the β1 phase and from the β1 phase to the β phase. It was. The elongated precipitate 2 that appears here has at least one of a β ′ phase, a β1 phase, and a β phase as a phase state, and a β ′ phase, a β1 phase, a β phase It was found that the metal composition as the phase was Mg ₅ Gd or Mg ₇ Gd, or Mg ₅ Gd and Mg ₇ Gd.

The composition of the β ′ phase is Mg ₇ Gd, and the β1 phase and the β phase are Mg ₅ Gd. Since the β1 phase and the β phase have the same composition but different structures, they are distinguished from the β1 phase and the β phase. That is, as a criterion for discrimination, the structure of Mg ₅ Gd is a hexagonal close-packed structure as the β1 phase, and the structure of Mg ₅ Gd is a body-centered cubic lattice as the β phase. With this Mg ₅ Gd and / or Mg ₇ Gd, the magnesium alloy material 1 improves the strength of the alloy while maintaining the elongation. Note that the structural change occurs even though the Mg ₅ Gd is the same because the β ′ phase changes to the β1 phase due to thermal energy, and there may be cases where both are mixed during the change depending on the heat treatment conditions. .

As shown in FIGS. 3 and 4, the β ′ phase, which is the long precipitate 2, appears as a state where Mg ₇ Gd is aligned and aligned in parallel. Further, as shown in FIG. 4, the β1 phase which is the long precipitate 2 appears in a zigzag state with the black short needle-like or plate-like substances alternately changing directions. Further, as shown in FIG. 5, the β phase as the long precipitate 2 appears in the center of the photograph as an elongated needle or plate. 3 to 5, a matrix appears around the elongated precipitate 2 (at least one of β ′ phase, β1 phase, and β phase).

(Long period laminate structure and its interval)
The long period ordered structure (LPO or LPSO for short) 3 is, for example, 14 regular lattices and 14 regular lattices arranged again through an antiphase shift. Several times the structure of the unit is made. Such a long-period structure is called a long-period multilayer structure (long-period multilayer structure phase). This phase appears in a slight temperature range between the regular and irregular phases. In the figure diffracted by electron beam, the reflection of the regular phase is split and a diffraction spot appears at a position corresponding to a period of 10 times. It is known that the long-period laminated structure 3 appears in an intermetallic compound or the like.

In addition, when the Mg—Zn—RE alloy is cast and solidified, Mg ₃ Gd (Mg ₃ Zn ₃ Tb ₂ or Mg ₂₄ Tm ₅ ) crystallizes at the grain boundary, The solid solution is formed (solution) by the heat treatment, and the long precipitate 2 and the long-period laminated structure 3 are precipitated by the solid solution and heat treatment.

(Alloy composition)
[Zn: 0.5-3 atoms (at)%]
If Zn is less than 0.5 at%, Mg ₃ Gd cannot be obtained and the strength is lowered. Further, if Zn exceeds 3 at%, the strength improvement corresponding to the addition amount cannot be obtained, and the elongation decreases (brittle). Accordingly, Zn is in the range of 0.5 to 3 at% here.

[RE (one or more of Gd, Tb, Tm): 1 to 5 atomic%]
Gd, Tb, and Tm do not cause the long precipitates 2 or the long-period laminated structure 3 to appear only by casting, but the solid precipitates 2 and long precipitates are formed by solid solution and heat treatment under predetermined conditions after casting. The periodic laminated structure 3 is deposited. In the magnesium alloy material 1, the long-period laminated structure 3 can be deposited under the heat treatment conditions to improve the strength. However, in order to obtain higher strength, Mg ₃ Gd (Mg ₃ Zn ₃ Tb ₂ or Mg ₂₄ Tm ₅ ) to form a long precipitate 2 by solid solution and heat treatment, or Mg ₃ Gd (Mg ₃ Zn ₃ Tb ₂ or Mg ₂₄ Tm ₅ ) solid solution and heat treatment to form a long precipitate This is to precipitate the product 2 and to mix Mg ₃ Gd ((Mg ₃ Zn ₃ Tb ₂ or Mg ₂₄ Tm ₅ ) to be crystallized.

For this reason, the RE made of at least one of Gd, Tb, and Tm in the magnesium alloy material 1 requires a predetermined amount. When at least one of Gd, Tb, and Tm in the magnesium alloy material 1 is less than 1 at% in total, Mg ₃ Gd (Mg ₃ Zn ₃ Tb ₂ or Mg ₂₄ Tm ₅ ), long precipitate 2 and long The periodic laminated structure 3 cannot be deposited, and if the total amount exceeds 5 at%, the strength improvement corresponding to the added amount cannot be obtained and the elongation decreases. Therefore, RE which consists of at least 1 sort (s) of Gd, Tb, and Tm in the magnesium alloy material 1 is made into the range of 1-5 at% here in total.

  Therefore, the magnesium alloy material 1 has a composition by atomic% in the alloy composition within a range represented by the composition formula Mg (100-ab) ZnaREb (in the composition formula, 0.5 ≦ a ≦ 3, 1 ≦ b ≦ 5). In the present invention, in addition to the components described above, other components can be added within the range of unavoidable impurities within a range that does not affect the effect of the magnesium alloy of the present invention, and contribute to, for example, miniaturization. Zr may be contained in an amount of about 0.1 to 0.5 at%.

Next, a method for producing a magnesium alloy material will be described.
FIGS. 6A and 6B are flowcharts showing a method for manufacturing a magnesium alloy material, and FIG. 7 is a graph schematically showing the relationship between the temperature and time of solution treatment and heat treatment of the magnesium alloy material.

  As shown to Fig.6 (a), the magnesium alloy material 1 is first cast by casting process S1. Here, the magnesium alloy material 1 is represented by the composition formula Mg (100-ab) ZnaREb, and RE is Gd. The cast material thus cast is then subjected to a solution treatment (RE is formed into a solid solution) in the solution treatment step S2. As an example, the solution treatment temperature at this time is 520 ° C. for 2 hours (see FIG. 7). In the cast material, the compound of Mg and Gd (Tb, Tm) generated by casting by the solution treatment is dissolved in the matrix to form a solid solution. In addition, it is preferable to hold | maintain a solution treatment at 500 degreeC or more for 2 hours or more.

Further, a first heat treatment step S3 is performed in which the cast material that has undergone solution treatment is heat-treated under predetermined conditions. Then, after the first heat treatment step S3, a second heat treatment step S4 is further performed under predetermined conditions. By performing the first heat treatment step S3, the long-period stacked structure 3 is precipitated, and by performing the second heat treatment step S4, long precipitates (X phase = β ′ phase, β1 phase, β1 phase, β phase) 1) 2 is deposited. In addition to these precipitates, crystallized Mg ₃ Gd (Mg ₃ Zn ₃ Tb ₂ or Mg ₂₄ Tm ₅ ) and Mg ₃ Zn ₃ Gd ₂ may be mixed.

  In the first heat treatment step, when heat treatment temperature (° C.) is y and heat treatment time (h) is x, −12 [ln (x)] + 375 <y <527 and 0.5 ≦ x <300 (First heat treatment condition). The second heat treatment step is performed under the condition of −18 [ln (x)] + 240 <y <−12 [ln (x)] + 375 and 2 <x <300 (second condition) Heat treatment conditions).

  When the first heat treatment step S3 and the second heat treatment step S4 are performed under predetermined conditions, as the magnesium alloy material 1, long precipitates (X phase = β ′ phase, β1 phase, β phase, which can particularly improve strength) 2) and a phase region structure in which the long-period stacked structure 3 is deposited. FIG. 8 is a graph showing areas of precipitates that precipitate in the metal structure at the heat treatment temperature and the heat treatment time.

As shown in FIG. 8, the range in which long precipitates (X phase: at least one of Xphase = β ′ phase, β1 phase, and β phase) 2 precipitate is the same as the first heat treatment condition described above, which is a high temperature condition. The range in which the long-period stacked structure 3 is deposited is the range of the second heat treatment condition described above, which is a low temperature condition. The range surrounded by the solid line indicates the approximate range of the heat treatment conditions, and the curves indicating the areas where various precipitates precipitate also indicate the approximate areas. In other words, the ranges (zones) where various precipitates are deposited are not strictly defined by temperature conditions, and therefore these ranges are shown as approximate ranges here for convenience. In FIG. 8, the unit of temperature is indicated by K for convenience. In addition, together with the elongated precipitate 2 and the long-period laminate structure 3, a Mg ₃ Gd precipitate may also precipitate. Magnesium alloy material 1 can improve mechanical properties such as tensile strength, elongation, and 0.2% proof stress as a whole by mainly forming long precipitates 2 and long-period laminated structure 3. Yes (see examples).

As an example of the temperature condition, when heat treatment is performed at 500 ° C. for 10 hours and then at 200 ° C. for 100 hours, at least one of β ′ phase, β1 phase, and β phase that are long precipitates 2 and a long-period laminated structure 3 is deposited (see FIG. 2).
Thus, when the practical range is taken into consideration, the heat treatment temperature range of the magnesium alloy material 1 is −12 [ln (x)] + 375 <y <527, which is the above-described high temperature condition, and 0. The range shown in 5 ≦ x <300, and −18 [ln (x)] + 240 <y <−12 [ln (x)] + 375, which is the low temperature condition described above, and 2 <x <300 It becomes a range.

  The heat-treated casting is then subjected to a plastic working step S5 in which the cast material heat-treated in the second heat treatment step S4 is subjected to plastic working as necessary. The plastic processing in the plastic processing step S5 may be extrusion processing or forging processing. The plastic processed product that has undergone plastic processing will have significantly improved tensile strength, elongation, and 0.2% yield strength. The magnesium alloy material 1 subjected to the extrusion process which is the plastic processing step S5 by performing the first heat treatment step S3 and the second heat treatment step S4 has higher tensile strength, elongation and 0.2% than those not subjected to the extrusion process. The value of proof stress is shown (refer an Example).

In addition, when the tensile strength, elongation, and 0.2% proof stress are improved, the magnesium alloy material 1 has a long precipitate (at least one of β ′ phase, β1 phase, and β phase) 2 and a long-period laminate. It is important that the structure 3 is provided. In addition, even when a crystallized product of Mg ₃ Gd (Mg ₃ Zn ₃ Tb ₂ or Mg ₂₄ Tm ₅ ) is precipitated, a long precipitate (β ′ Phase, β1 phase, at least one of β phase) 2 and long-period laminate structure 3 are precipitated, the tensile strength, elongation, and 0.2% proof stress are improved.

  The plastic working step S5 shown in FIG. 6A is performed according to the purpose of the magnesium alloy material 1 because the strength is improved by applying plastic working (extrusion processing, forging processing) to the heat-treated casting. It doesn't matter. In addition, the magnesium alloy material 1 after the plastic working is processed into a predetermined shape by cutting or the like to be commercialized. Here, as a method for manufacturing the magnesium alloy material 1, the casting process S1 to the plastic working process S5 are shown as a series of processes. However, the casting process S1 to the second heat treatment process S4 are taken as a series of processes, and plastic working is performed. Step S5 may be performed at the product insertion destination.

As another embodiment, as shown in FIG. 6B, the cast material cast in the casting step S11 is subjected to solution treatment in the solution treatment step S12, and the cast material subjected to solution treatment is subjected to the first heat treatment. A manufacturing method in which after heat treatment at a predetermined temperature in step S13, the heat-treated cast material is subjected to plastic working in plastic working step S14, and the cast material subjected to plastic working is subjected to heat treatment in second heat treatment step S15. It is good. The plastic processing in the plastic processing step S14 may be extrusion processing or forging processing.
In the magnesium alloy material 1 subjected to the second heat treatment step S15 after performing the first heat treatment step S13 and performing the extrusion process or the like, which is the plastic working step S14, the tensile strength is higher than that in which the extrusion process or the like is not performed. , Elongation and 0.2% proof stress are remarkably improved.

  Further, as another embodiment, the order of the first heat treatment (high temperature heat treatment) and the second heat treatment (low temperature heat treatment) may be reversed. That is, the high temperature heat treatment may be performed after the low temperature heat treatment.

  Next, examples of the present invention will be described. In addition, the Example shown here is an example and does not limit this invention. FIG. 9 is a block diagram showing each process for evaluating the mechanical properties, and FIGS. 10A, 10B, 11A, and 11B show heat treatment under predetermined conditions on the cast ingot. FIG. 12 is a TEM photograph when a plastic working is performed after the cast ingot is subjected to heat treatment under a predetermined condition.

As a magnesium alloy material, Zn was 1 at%, Gd was 2 at%, and the remainder was put into a melting furnace as Mg and an inevitable impurity Mg—Zn—Gd alloy, and was melted by flux refining. Next, as shown in FIG. 9, the heat-melted material is cast with a mold (S1) to produce an ingot (cast material) of φ29 mm × L60 mm, and the cast ingot is melted at 520 ° C. for 2 hours. (S2), then heat treatment is performed at each temperature (first heat treatment: S3, second heat treatment: S4), and plastic processing (extrusion processing) (S5) is performed at an extrusion temperature of 400 ° C. with an extrusion ratio of 10. And those which were not subjected to plastic working (extrusion) (S5) were manufactured and subjected to a tensile test at room temperature. The strain rate in the tensile test is ε = 5.0 × 10 ⁻⁴ (s ⁻¹ ), that is, 5.0 × 10 ⁻⁴ mm / s. Further, the solution treatment and the heat treatment are performed in a muffle furnace under the conditions shown in Tables 1 and 2. In FIG. 9, the solution treatment, the first heat treatment, and the second heat treatment are collectively described as heat treatment.

These results are shown in Tables 1 and 2.
In Tables 1 and 2, the conditions within the scope of the present invention are Examples 1 to 14, and the conditions outside the scope of the present invention are Comparative Examples 1 to 16, and the heat treatment conditions, the state of the structure, etc. And 0.2% proof stress, tensile strength, and elongation. Table 1 shows a case where plastic processing (S5) is not performed, and Table 2 shows a case where plastic processing (S5) is performed after the second heat treatment (S4). And about the main deposit, the thing by which precipitation was confirmed is shown by "(circle)", and the thing which was not confirmed is shown by "-".

  As shown in Tables 1 and 2, the Mg alloy materials of Examples 1 to 14 all have LPSO and long precipitates in the metal structure, and 0.2% compared to the comparative example. Mechanical properties such as proof stress, tensile strength and elongation are improved overall. On the other hand, Comparative Examples 1 to 16 do not have any one or both of LPSO and long precipitates in the metal structure, so 0.2% proof stress and tensile strength compared to the examples. In addition, mechanical properties such as elongation are generally deteriorated. In addition, it can be seen that 0.2% proof stress, tensile strength, and elongation are remarkably improved in the case where the plastic working (S5) is performed, compared to the case where the plastic working (S5) is not performed.

  Moreover, the state of the metal structure of a typical thing among the said Example and comparative example is shown to Fig.10 (a), (b), Fig.11 (a), (b), and FIG. As shown in FIGS. 10A and 10B, the long precipitates are not precipitated only by the heat treatment at 500 ° C. × 10 h and only by the heat treatment at 500 ° C. × 2 h. As shown in FIGS. 11 (a) and 11 (b), LPSO and long precipitates are precipitated in the case of heat treatment at 200 ° C. × 100 h after heat treatment at 500 ° C. × 10 h. Furthermore, as shown in FIG. 12, the heat treatment of 200 ° C. × 100 h after the heat treatment of 500 ° C. × 10 h, followed by plastic working, precipitates a lot of LPSO and long precipitates.

  Thus, the magnesium alloy material has an X phase (acicular precipitate or plate-like precipitate = long precipitate = any one of β ′ phase, β1 phase, β phase), a long-period laminated structure, , It is possible to use Mg-Zn-RE alloy as a material having further excellent mechanical properties. Note that the β phase, β1 phase, and β ′ phase differ depending on the size of the product or the crystal grain size at the time of casting, and the structure form of each part differs even in the same heat treatment, and these phases exist alone or in a mixture. It is possible that

  As described above, the magnesium alloy material and the manufacturing method thereof according to the present invention have been described in detail with reference to the best embodiment and examples, but the gist of the present invention is not limited to the above-described content, It should be construed broadly based on the claims. Needless to say, the contents of the present invention can be widely modified and changed based on the above description.

(A) is a TEM photograph showing a state in which at least one of a β phase, a β ′ phase, and a β1 phase and a long-period laminated structure appear in the metal structure of the magnesium alloy material according to the present invention. (B) is a TEM photograph showing the appearance of the GP band that appeared in the metal structure of the magnesium alloy material according to the present invention. In the metal structure of the magnesium alloy material according to the present invention, a state in which at least one of a β phase, a β ′ phase, and a β1 phase, a long-period stacked structure, and a crystallized product of Mg ₃ Gd appear It is a TEM photograph which shows. It is a TEM photograph which shows the metal structure of the magnesium alloy material which concerns on this invention, and shows the state which (beta) 'phase (elongate precipitate) has appeared. It is a TEM photograph which shows the metal structure of the magnesium alloy material which concerns on this invention, and shows the state which (beta) 'phase and (beta) 1 phase (elongate precipitate) have appeared. It is a TEM photograph which shows the metal structure of the magnesium alloy material which concerns on this invention, and shows the state which (beta) phase (elongate precipitate) has appeared. (A), (b) is a flowchart which shows the manufacturing method of the magnesium alloy material based on this invention. It is a graph which shows typically the relationship between the solution treatment of the magnesium alloy material which concerns on this invention, and the temperature of heat processing, and time. It is a graph which shows the area | region of the precipitate which precipitates in the metal structure in the heat processing temperature and heat processing time on the conditions which concern on this invention. It is a block diagram which shows each process for performing evaluation of a mechanical property when demonstrating the Example of this invention. (A), (b) is a TEM photograph when the cast ingot used in the Example of this invention is heat-processed on predetermined conditions. (A), (b) is a TEM photograph when the cast ingot used in the Example of this invention is heat-processed on predetermined conditions. It is a TEM photograph when performing plastic working after heat-treating predetermined conditions on the cast ingot used in the example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnesium alloy material 2 Elongate precipitate (Acicular precipitate or plate-like precipitate: X phase = any one of β 'phase, β1 phase, β phase)
3 Long-period laminated structure (LPSO)

Claims (6)

  Zn as an essential component, and at least one or more of Gd, Tb, and Tm as RE, and the balance is Mg—Zn—RE alloy composed of Mg and inevitable impurities, and the Mg—Zn—RE alloy A magnesium alloy material characterized in that an alloy structure of an alloy has at least one of a β phase, a β ′ phase, and a β1 phase and a long-period laminated structure.   The magnesium alloy material according to claim 1, wherein the Zn has a component range of 0.5 to 3 atomic% and the RE has a component range of 1 to 5 atomic%. In the method for producing a magnesium alloy material,
Casting that forms a cast material by casting an Mg—Zn—RE alloy containing Zn as an essential component and at least one of Gd, Tb, and Tm as RE and the balance being Mg and inevitable impurities. Process,
A solutionizing step for forming a solution of the cast material;
A first heat treatment step of heat-treating the solution cast material under predetermined conditions;
A second heat treatment step for performing heat treatment under a predetermined condition after the first heat treatment step,
In the first heat treatment step, when the heat treatment temperature (° C.) is y and the heat treatment time (h) is x,
-12 [ln (x)] + 375 <y <527, and 0.5 ≦ x <300.
In the second heat treatment step, when the heat treatment temperature (° C.) is y and the heat treatment time (h) is x,
-18 [ln (x)] + 240 <y <-12 [ln (x)] + 375, and the method of manufacturing a magnesium alloy material characterized by being performed in the range of 2 <x <300. In the method for producing a magnesium alloy material,
Casting that forms a cast material by casting an Mg—Zn—RE alloy containing Zn as an essential component and at least one of Gd, Tb, and Tm as RE and the balance being Mg and inevitable impurities. Process,
A solutionizing step for forming a solution of the cast material;
A first heat treatment step of heat-treating the solution cast material under predetermined conditions;
After the first heat treatment step, a second heat treatment step of performing heat treatment under a predetermined condition;
A plastic working step of performing plastic working on the cast material heat-treated in the second heat treatment step,
In the first heat treatment step, when the heat treatment temperature (° C.) is y and the heat treatment time (h) is x,
-12 [ln (x)] + 375 <y <527, and 0.5 ≦ x <300.
In the second heat treatment step, when the heat treatment temperature (° C.) is y and the heat treatment time (h) is x,
-18 [ln (x)] + 240 <y <-12 [ln (x)] + 375, and the method of manufacturing a magnesium alloy material characterized by being performed in the range of 2 <x <300. In the method for producing a magnesium alloy material,
Casting that forms a cast material by casting an Mg—Zn—RE alloy containing Zn as an essential component and at least one of Gd, Tb, and Tm as RE and the balance being Mg and inevitable impurities. Process,
A solutionizing step for forming a solution of the cast material;
A first heat treatment step of heat-treating the solution cast material under predetermined conditions;
A plastic working step of performing plastic working on the cast material heat treated in the first heat treatment step;
A second heat treatment step of heat-treating the cast material subjected to the plastic working under a predetermined condition,
In the first heat treatment step, when the heat treatment temperature (° C.) is y and the heat treatment time (h) is x,
-12 [ln (x)] + 375 <y <527, and 0.5 ≦ x <300.
In the second heat treatment step, when the heat treatment temperature (° C.) is y and the heat treatment time (h) is x,
-18 [ln (x)] + 240 <y <-12 [ln (x)] + 375, and the method of manufacturing a magnesium alloy material characterized by being performed in the range of 2 <x <300.   The method for producing a magnesium alloy material according to claim 4 or 5, wherein the plastic working in the plastic working step is an extrusion process or a forging process.