JPH0790462A - High strength magnesium alloy and its production - Google Patents

Abstract

PURPOSE:To prevent deterioration in the strength of a magnesium alloy at a high temp. by subjecting an Mg-Al series alloy produced by a rapid solidifying method to plastic working at a specified temp. and dispersing intermetallic compounds into a mother phase constituted of fine crystals. CONSTITUTION:Alloy powder having a compsn. of MgaAlbXc is produced by a rapid solidifying method. In the formula, X denotes one or >= two kinds of elements selected from Y, Ce, La, Nd, Pr, Sm and Mm (mish metal), and as for (a), (b) and (c), by atomic%, 77.5<=a<=95%, 2%<=b<=15% and 3%<c<=7.5% are satisfied. This rapidly solidified alloy powder is subjected to plastic working at <=450 deg.C to form its shape into a desired one. Thus, its structure is formed into a one in which one or >= two kinds selected from the group of Mg-Al series, Mg-X series and Al-X series are dispersed into a mother phase constituted of fine crystals. As for its high temp. strength, ultimate tensile strength at 200 deg.C is regulated to about >=0.8 by a ratio to the value at a room temp., and deterioration in its strength at a high temp. is small.

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 specifically 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, for example, from JP-A-62-83446 that high strength and excellent corrosion resistance are realized by rapidly solidifying magnesium alloy. The magnesium alloy of this publication has the general formula: Mgbal Ala Znb
Xc (where X is Mn, Ce, Nd, Pr, Y, and /
Or Ag, 0 ≦ a ≦ 15 atomic%, 0 ≦ b ≦ 4 atomic%,
0.2 ≦ c ≦ 3 atomic%, 2 ≦ a + b ≦ 15 atomic%). A powder of a rapidly solidified alloy having this composition can be hot-compressed to form a bulk material, and its strength is about 513 MPa in ultimate tensile strength.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The above-mentioned conventional rapidly solidified Mg alloy is used in the range of 200 to 30 such as a piston.
It has been found that the strength is remarkably reduced when the component is used at a high temperature of about 0 ° C. Further, it has been found that when the rapidly solidified Mg alloy is processed at a temperature of about 300 to 400 ° C., which has good workability, the crystal grains become coarse and the strength is significantly reduced.

Therefore, it is an object of the present invention 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 a rapidly solidified Mg alloy is subjected to plastic working to form materials of various shapes.

[0005]

The first aspect of the present invention is to provide a compound represented by the 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
7.5 atomic% ≤ a <95 atomic%, 2 atomic% ≤ b ≤ 15 atomic%, 3 atomic% <c <7.5 atomic%), and Mg- The present invention relates to a high-strength magnesium alloy 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 The second of the present invention is to rapidly solidify the alloy having the above composition,
After that, the rapidly solidified alloy is subjected to plastic working at a temperature of 450 ° C. or lower, and a matrix consisting of microcrystals is formed into a Mg—Al-based or Mg-X-based matrix.
System or one or two selected from the group consisting of Al-X system
The present invention relates to a method for producing a high-strength magnesium alloy having a structure in which one or more intermetallic compounds are dispersed.

First, the reasons for limiting the composition of the magnesium alloy of the present invention will be described. M which is the main component of magnesium alloy
When the content of g is less than 77.5 atomic% (the percentages below are atomic% unless otherwise specified), the feature of the magnesium alloy that it is lightweight is lost, and the ratio of the matrix phase is reduced and the toughness decreases. Invite. On the other hand, when the content of Mg exceeds 95%, the amount of intermetallic compound precipitated in the Mg mother phase becomes insufficient, and the room temperature and high temperature strength decreases.

Al is a metal with an intermetallic compound with Mg and an X component (one or more selected from the group consisting of Y, Ce, La, Nd, Pr, Sm, and Mm (Misch metal)). Intermetallic compounds are formed, and these intermetallic compounds are further finely dispersed in the fine Mg matrix phase to enhance the strength without impairing the toughness. Al and X components (Y, Ce, L
The content of one or more selected from the group consisting of a, Nd, Pr, Sm, and Mm (Misch metal) needs to be within the range shown in FIG. That is, to the left of the AD line (Al = 2%) and the CD line (X = 3)
%) Above and below that, the amount of intermetallic compound dispersed becomes insufficient, resulting in a decrease in strength at room temperature and high temperature. Also AB line (x
= 7.5%) and the right side of the BC line (Al = 15%), the intermetallic compound dispersed in the matrix becomes coarse and the material becomes brittle. Therefore, the Al content 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 comprises a matrix phase, that is, a phase having a Mg crystal structure, and a Mg-Al structure.
System, Mg-X system and / or Al-generated on the low X and high Al side
It is composed of a dispersed phase of an X-based intermetallic compound. The Mg matrix phase is a submicron crystallite, and a finer dispersed phase of the intermetallic compound is dispersed therein. Since these Mg-Al-based, Mg-X-based, and Al-X-based intermetallic compounds are thermally stable, fine, and have a sufficient amount, deformation and growth of the parent phase are suppressed and high temperature is achieved. To reduce the decrease in strength. In order to form a structure in which a finer intermetallic compound is dispersed in the fine Mg matrix phase as described above, the magnesium alloy having the above composition is rapidly solidified so that the Al and X components are sufficiently contained in the non-equilibrium phase. Solid solution,
After that, a method of precipitating these as fine intermetallic compounds by heat treatment is adopted. As this method, it is preferable to employ a method of heat treatment at 450 ° C. or lower or plastic working at 450 ° C. or lower. The lower limit of the heat treatment or plastic working temperature is preferably 130 ° C or higher.

Next, a method of processing a magnesium alloy according to the second aspect of the present invention will be described. In this method, a rapidly solidified alloy having the above composition is plastically worked at a temperature of 450 ° C. or lower to obtain a material having a desired shape and size. The plastic working temperature was set to 450 ° C. or lower because at a temperature above this, the Mg matrix phase coarsens and the non-equilibrium phase decomposes to produce fine intermetallic compounds, and as a result, desired characteristics are obtained. This is because it is hard to be beaten.

The embodiments of the method of the present invention will be described below. The rapid solidification of molten Mg alloy is generally known as rapid solidification method, for example, gun method for producing flakes, piston-anvil method, centrifugal method for producing continuous ribbons, single roll method, twin method. A roll method, a spray method for producing powder, a high-pressure gas atomizing method, or a spinning submerged spinning method for producing fine wires can be used. Among these methods, a cooling rate of 10 2 to 10 6 k / s can be easily obtained,
A single roll method, a twin roll method, or a high-pressure gas atomization method, in which almost all Al and X components are in solid solution, are particularly suitable.

In order to produce the Mg alloy ribbon by the single roll method and the twin roll method, the molten alloy is sprayed onto a copper or steel roll having a diameter of 30 to 300 mm which rotates 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 can be obtained.

Further, in order to obtain the Mg alloy powder by the high pressure gas atomization method, the alloy melt flowed down from the melt nozzle should be 4 to
High-pressure nitrogen gas of 15 MPa, argon gas, helium gas, etc. are blown to finely divide the molten metal, and at the same time rapidly solidified. More preferably, by classifying the fine powder, the powder containing a large amount of Al and the X component in solid solution may be subjected to plastic working.

The Mg alloy obtained by the above-mentioned rapid solidification method is
Although it is possible to perform plastic working as it is, in the case of a thin strip or a thin wire, it is preferable to crush and then fill a can made of Cu, Al or an alloy thereof and perform plastic working. At this time, it is preferable to handle the rapidly solidified powder in an atmosphere of high cleanliness with an oxygen content of 1 ppm or less in order to suppress the oxidation of the rapidly solidified material after the rapid solidification and filling into the metal can.
Further, it is preferable that the powder filled in the metal can is subjected to vacuum degassing before being plastically worked.

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 as a ratio with respect to the value at room temperature, and the strength is not significantly reduced at high temperature.

[0016]

【Example】

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

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

[0018]

[Table 1] No. Composition Extrusion temperature Intermetallic compound phase UTS elongation 1 Mg94.5Al2Y3.5 300 ℃ 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 0.1 7 Mg80Al5Y15 400 Mg24Y5 382- Note 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 500 to 600 MPa, which is extremely high. Further, it can be seen 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 strength reduction at a high temperature and having a desired shape and size can be obtained by various processing methods such as extrusion.

[Brief description of drawings]

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 000003207 Toyota Motor Corporation 1 Toyota Town, Toyota City, Aichi Prefecture (72) Inventor Ken Masumoto 3-8-22 Uesugi, Aoba-ku, Sendai City, Miyagi Prefecture (72) Inventor Akihisa Inoue Banuchi, Kawauchi, Aoba-ku, Sendai-shi, Miyagi 11-806 (72) Inventor Hidehiko Horikiri 1-9-9 Yaesu, Chuo-ku, Tokyo Imperial Piston Ring Co., Ltd. (72) Akira Kato Toyota, Aichi Prefecture City Toyota-City, Toyota City

Claims (2)

[Claims] 1. A general formula: Mga Alb Xc (where X is one or more elements selected from the group consisting of Y, Ce, La, Nd, Pr, Sm and Mm (Misch metal), 77. .5 atomic% ≤ a <95 atomic%, 2 atomic% ≤ b
≦ 15 atomic%, 3 atomic% <c ≦ 7.5 atomic%), and a Mg mother phase composed of microcrystals in a Mg-Al system,
1 selected from the group consisting of Mg-X system and Al-X system
A high-strength magnesium alloy having a structure in which one or more intermetallic compounds are dispersed. 2. An alloy having the composition of claim 1 is rapidly solidified, and then the rapidly solidified alloy is subjected to plastic working at a temperature of 450 ° C. or lower, and a matrix phase composed of fine crystals is formed into a Mg—Al-based, M-based alloy.
A method for producing a high-strength magnesium alloy, which has a structure in which one or more intermetallic compounds selected from the group consisting of g-X type and Al-X type are dispersed.