JP3193208B2 - High strength magnesium alloy and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength magnesium alloy and a method for producing the same, and more particularly, to a proposal for further improving the strength characteristics of a magnesium alloy obtained by rapid solidification.

[0002]

2. Description of the Related Art It is known from JP-A-62-83446 to realize high strength and excellent corrosion resistance by rapidly solidifying a magnesium alloy. The magnesium alloy of this publication has a general formula: Mgbal Ala Znb
Xc (where X is Mn, Ce, Nd, Pr, Y, and / or
Or Ag, 0 ≦ a ≦ 15 at%, 0 ≦ b ≦ 4 at%,
0.2 ≦ c ≦ 3 at%, 2 ≦ a + b ≦ 15 at%). A rapidly solidified alloy powder having this composition can be made into a bulk material by hot compression, and its strength is as high as about 513 MPa in ultimate tensile strength.

[0003]

The above-mentioned conventional rapidly solidified Mg alloy is used for 200 to 30 minutes, such as a piston.
It has been found that when a part is used at a high temperature of about 0 ° C., the strength is significantly reduced. Further, it was also found that when the above-mentioned rapidly solidified Mg alloy was worked at a temperature of about 300 to 400 ° C. with good workability, the crystal grains became coarse and the strength was significantly reduced.

Accordingly, an object of the present invention is to provide a rapidly solidified Mg alloy having excellent room temperature and high temperature strength. A further object of the present invention is to suppress a decrease in strength when plasticizing a rapidly solidified Mg alloy to form materials of various shapes.

[0005]

A first aspect of the present invention is to provide a compound represented by the following general formula: Mga Alb Xc (where X is Y, Ce,
La, Nd, Pr, Sm, and Mm (Misch metal)
One or more elements selected from the group consisting of
7.5 atomic% ≦ a <95 atomic%, 2 atomic% ≦ b ≦ 15 atomic%, 3 atomic% <c <7.5 atomic%), and Mg— A high-strength magnesium alloy characterized by having a structure in which one or more intermetallic compounds selected from the group consisting of Al-based, Mg-X-based, and Al-X-based are dispersed; and A second aspect of the present invention is to rapidly solidify an alloy having the above composition,
Thereafter, the rapidly solidified alloy is subjected to plastic working at a temperature of 450 ° C. or less, and the matrix composed of microcrystals is made of Mg-Al, Mg-X
Or 2 selected from the group consisting of a system and an Al-X system
The present invention relates to a method for producing a high-strength magnesium alloy having a structure in which at least one kind of intermetallic compound is dispersed.

First, the reasons for limiting the composition of the magnesium alloy of the present invention will be described. M, the main component of magnesium alloy
When the content of g is less than 77.5 atomic% (the percentage is hereinafter atomic% unless otherwise specified), the feature of the magnesium alloy that it is lightweight is lost, and the ratio of the parent phase is reduced and the toughness is reduced. Invite. On the other hand, if the Mg content exceeds 95%, the amount of the intermetallic compound precipitated in the Mg parent phase becomes insufficient, resulting in a decrease in the strength at room temperature and high temperature.

Al is an intermetallic compound with Mg and a metal with X component (one or more selected from the group consisting of Y, Ce, La, Nd, Pr, Sm, and Mm (mish metal)). Intermetallic compounds are formed, and these intermetallic compounds are further finely dispersed in a fine Mg matrix to increase the strength without impairing toughness. Al and X components (Y, Ce, L
The content of a, Nd, Pr, Sm, and Mm (one or more selected from the group consisting of misch metal) must be in the range shown in FIG. That is, the left side of the AD line (Al = 2%) and the CD line (X = 3
%) On the upper side and the lower side, the amount of the intermetallic compound dispersed is insufficient, and the room temperature and high temperature strengths are lowered. AB line (x
= 7.5%) and on the right side of the BC line (Al = 15%), the intermetallic compound dispersed in the parent phase coarsens and the material becomes brittle. Therefore, the content of Al is 2% ≦ b ≦
It is necessary that the content of the X component is 15% and the content of the X component is 3% <c ≦ 7.5%.

Next, the structure of the magnesium alloy of the present invention will be described. The structure of the magnesium alloy of the present invention includes a parent phase, that is, a phase having a crystal structure of Mg, and a Mg-Al
System, Mg-X system and / or Al- formed on low X high Al side
It is composed of a dispersed phase of an X-based intermetallic compound. The Mg matrix is a submicron microcrystal, in which a finer dispersed phase of an intermetallic compound is dispersed. These Mg-Al-based, Mg-X-based, and Al-X-based intermetallic compounds are thermally stable, are fine and have a sufficient amount, so that deformation and growth of the parent phase are suppressed and high temperatures are obtained. In the strength reduction. In order to form a structure in which finer intermetallic compounds are dispersed in the fine Mg matrix, the magnesium alloy having the above-described composition is rapidly solidified to sufficiently reduce the Al and X components in the non-equilibrium phase. Solid solution,
Thereafter, a method of precipitating them as fine intermetallic compounds by heat treatment is employed. As this method, a method of performing heat treatment preferably at 450 ° C. or lower or plastic working at 450 ° C. or lower can be adopted. The lower limit of the heat treatment or plastic working temperature is preferably 130 ° C. or higher.

Next, a second method for processing a magnesium alloy according to the present invention will be described. In this method, a rapidly solidified alloy having the above composition is subjected to plastic working at a temperature of 450 ° C. or less to obtain a material having a desired shape and dimensions. The reason why the temperature of the plastic working is set to 450 ° C. or less is that at a temperature higher than this, the Mg matrix becomes coarse and the intermetallic compound formed by decomposition of the non-equilibrium phase is not fine, so that the desired characteristics can be obtained. Because it is hard to be.

Hereinafter, an embodiment of the method of the present invention will be described. The rapid solidification of molten Mg alloy is performed by various methods generally known as rapid solidification method, for example, a gun method for producing a thin section, a piston / anvil method, a centrifugal method for producing a continuous ribbon, a single roll method, and a twin method. A roll method, a spray method for producing powder, a high-pressure gas spraying method, a spinning method in a rotating liquid for producing fine wires, and the like can be used. Among these methods. A cooling rate of 10 ² to 10 ⁶ k / s is obtained, and Al and X
A single-roll method, a twin-roll method, or a high-pressure gas injection method, in which the components are almost completely dissolved, are particularly suitable.

In order to produce a Mg alloy ribbon by the single roll method and the twin roll method, a molten alloy is sprayed on a copper or steel roll having a diameter of 30 to 300 mm rotating at 300 to 10000 rpm. As a result, a ribbon having a width of 1 to 300 mm and a thickness of 5 to 500 μm is obtained.

In order to obtain the Mg alloy powder by the high pressure gas atomization method, it is necessary to add 4 to 4 times to the molten alloy flowing down from the molten metal nozzle.
A high-pressure nitrogen gas of 15 MPa, an argon gas, a helium gas, or the like is sprayed to finely divide the molten metal, and at the same time, rapidly solidify. It is more preferable to classify the fine powder so as to subject the powder having a large amount of solid solution of the Al and X components to plastic working.

The Mg alloy obtained by the above-mentioned rapid solidification method is:
Although it is possible to carry out plastic working as it is, in the case of a thin ribbon or a thin wire, it is preferable to pulverize and then fill a can made of Cu, Al or an alloy thereof and carry out plastic working. At this time, it is preferable to handle the rapidly solidified powder in a highly clean atmosphere having an oxygen content of 1 ppm or less in order to suppress oxidation of the rapidly solidified material from rapid solidification to filling in a metal can.
In addition, it is preferable to subject the powder filled in the metal can to vacuum degassing prior to plastic working.

As the plastic working method, various methods such as extrusion, forging, and rolling can be performed.

[0015]

The high-temperature strength in the present invention is such that the ultimate tensile strength at 200 ° C. is 0.8 or more in proportion to the value at room temperature, and the strength at high temperatures does not decrease much.

[0016]

【Example】

Example 1 An Mg alloy having a chemical composition shown in Table 1 was subjected to high frequency melting in an Ar atmosphere to produce a mother alloy. This mother alloy was melted at 850 ° C. in a high-frequency furnace in an Ar atmosphere, and then 9.8 MPa of A
The powder was made of fine crystalline metal by high pressure gas spraying with r gas. Among the atomized powders, those having a small particle size are rapidly quenched, and the solid solution amount of the added element is large. The obtained powder was classified, and powder having a diameter of 25 μm or less was extruded at a temperature of 150 to 400 ° C., a pressure of 200 to 1000 MPa, and an extrusion ratio of 10: 1, and was about 6 mm in diameter and about 270 m in length.
m, a columnar material having a density of 100% was obtained. The atmosphere to which the powder was exposed during the stages from powder preparation to extrusion was a high cleanness atmosphere in which both oxygen and moisture concentrations were 1 ppm or less. X-ray diffraction of the columnar material revealed that the intermetallic compound shown in Table 1 was M
Observed with g phase. In the table, unknown is an intermetallic compound that has not yet been identified.

Next, the columnar material was subjected to a tensile test using an Instron type tensile tester. The results are also shown in Table 1. The percentage of elongation is the ratio of the length of a tensile test piece.

[0018]

[Table 1] No. Composition extrusion temperature Intermetallic compound phase UTS elongation 1 Mg94.5Al2Y3.5 300 ° C Mg24Y5, unknown 583MPa 2.7% 2 Mg90Al5Y5 300 Mg24Y5, unknown 600 2.5 3 Mg82.5Al10Y7.5 250 Al2Y, Mg24Y5 560 1.8 4 Mg80Al15Y5 150 Al2Y, unknown 530 2.5 5 Mg92.5Al5Y2.5 250 Al2Y 425 4.8 6 Mg75Al15Y10 300 Al2Y, Mg24Y5 480 0.17 Mg80Al5Y15 400 Mg24Y5 382- Remarks No. 5, 6, 7-Comparative example

From Table 1, it can be seen that the ultimate tensile strength (UTS) of the Mg alloy of the present invention is extremely high at 500 to 600 MPa. Further, it is understood that the composition of the comparative example is a material having low strength or brittleness.

[0020]

As described above, the magnesium alloy according to the present invention has a high strength and a small decrease in strength at high temperatures. Further, according to the method of the present invention, a magnesium alloy having a high strength and a small decrease in strength at a high temperature and having a desired shape and dimensions can be obtained by various processing methods such as extrusion.

[Brief description of the drawings]

FIG. 1 is a graph showing a composition range of an X component and Al of a magnesium alloy of the present invention.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C22F 1/00 630 C22F 1/00 630A 685 685A (72) Inventor Takeshi Masumoto 3-8-22 Uesugi Uesugi, Aoba-ku, Sendai City, Miyagi Prefecture. (72) Inventor Akihisa Inoue 11-806 Kawauchi Residence, Kawauchi, Aoba-ku, Sendai, Miyagi Prefecture (72) Inventor Hidehiko Horikiri 1-9-9 Yaesu, Chuo-ku, Tokyo Inside Teikoku Piston Ring Co., Ltd. (72) Inventor Akira Kato 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (56) References JP-A-62-83446 (JP, A) JP-A-46-6202 (JP, A) JP-A-5-58 287429 (JP, A) JP-A-5-117798 (JP, A) JP-A-3-87339 (JP, A) JP-A-6-501056 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) C22C 45/0 0 C22C 23/00-23/06 C22F 1/06

Claims (3)

(57) [Claims] 1. The general formula Mg _a Al _b X _c (where X is Y, C
one or more elements selected from the group consisting of e, La, Nd, Pr, Sm and Mm (Misch metal), 77.5
Atomic% ≦ a <95 atomic%, 2 atomic% ≦ b ≦ 15 atomic%,
Having a composition consisting of 3 atomic% <c ≦ 7.5 atomic%), grain
The Mg matrix consisting of microcrystals with
-Having a structure in which one or more intermetallic compounds selected from the group consisting of Al, Mg-X and Al-X are dispersed, and having an ultimate tensile strength (UTS) of 500 to 60;
A high-strength magnesium alloy having a pressure of 0 MPa. 2. The high-strength magnesium alloy according to claim 1, wherein the one or more intermetallic compounds are precipitated from a Mg matrix solid solution. 3. An alloy having the composition of claim 1 is rapidly solidified to form a microcrystalline magnesium solid solution, and thereafter, the rapidly solidified alloy is subjected to plastic working at a temperature of 450 ° C. or less, and is made of microcrystals. A high-strength magnesium alloy having a structure in which one or more intermetallic compounds selected from the group consisting of Mg-Al, Mg-X, and Al-X are dispersed in a matrix; Production method.