JPH0649580A - High-strength magnesium alloy containing gadolinium and samarium - Google Patents

Abstract

PURPOSE: To improve the heat resistance and the strength at a room temperature of an Mg alloy by adding Gd and Sm whose the weight ratio and the total quantity are specified in Mg.

CONSTITUTION: This heat resistant high-strength Mg alloy has a composition making Gd and Sm contain so that the weight ratio of Gd:Sm is 1:0.3-0.5 and the total quantity is 4-25 wt.% and consisting of the balance Mg and inevitable impurities. Then, 0.8-5% at least one kind of element to be selected from a group of Ca, Y, Sc and lanthanoid (except Gd, Sm), is made to contain, as necessary. Further, ≤2% at least one kind of Zr and Mn is made to contain, as necessary. The effect of addition to improve the strength at a room temperature and a high temperature is superposed by using jointly Gd and Sm and the synergistic effect is achieved.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnesium alloy excellent in strength at room temperature and high temperature, and more particularly, it has sufficient strength even at high temperatures up to about 573K which is required for weight reduction of parts around pistons of automobile engines. It relates to a magnesium alloy having.

[0002]

2. Description of the Related Art Due to the increasing awareness of global environmental protection in recent years,
With the increasing demand for improved fuel efficiency of automobiles, the development of lightweight materials for automobiles has been strongly demanded.

Magnesium alloy has the lowest density among the metallic materials currently put into practical use, and is strongly expected as a lightweight material for automobiles in the future. Currently, the most commonly used magnesium alloy is Mg-Al-Zn-M.
n-based alloy (for example, AZ91 alloy = Mg-9Al-1Z
n-0.5Mn), peripheral technologies such as casting technology of this alloy are in the completion stage, and this alloy is first studied for weight saving of automobiles. Further, recently, as a heat-resistant magnesium alloy, a Mg-Y-Ln-based alloy in which lanthanoid (Ln) is added to magnesium (for example, WE54 = M
g-5Y-4Nd) and the like have been developed and are being studied as engine parts for automobiles.

[0004]

However, the above-mentioned Mg-Al-Zn-Mn-based alloy has a reduced strength at 393 K or higher and is not suitable for use in automobile engine parts where heat resistance is required. In addition, the above heat resistance Mg-Y-L
In Ln-containing alloys such as n-based alloys, since Ln is a heavy element, Ln tends to be biased downward in the molten metal, and Zr, which is used as an essential component for refining the cast structure, has an added yield. Is unstable and the cost is high. Further, such Mg-Y-Nd-Zr
4% by weight or more of expensive Y and 3% by weight of Nd
Since it is contained as described above, it is difficult to use for mass production of automobiles in terms of cost, and the strength is slightly insufficient at 573K.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is a novel material suitable for a material for automobile engine parts which is required to have both heat resistance and room temperature strength. Another object is to provide a heat-resistant high-strength magnesium alloy.

[0006]

As a result of various studies to solve the above problems, the present inventors have found that addition of an appropriate amount of gadolinium to magnesium improves room temperature and high temperature strength. . However, gadolinium is an expensive metal, and if gadolinium is added in an amount of 15% by weight or more, it becomes an extremely expensive alloy. As a result of various studies on alloy compositions that can obtain almost the same effect even if the amount of gadolinium added is reduced, it was found that it was effective to use gadolinium and samarium together in a prescribed ratio, and in addition to gadolinium and samarium. Further, the inventors have found that the room temperature and high temperature strength are further improved by further using at least one element selected from the group consisting of calcium, yttrium, scandium and lanthanoids (excluding gadolinium and samarium), and arrived at the present invention. .

That is, the magnesium alloy of the present invention excellent in strength at room temperature and high temperature contains gadolinium and samarium, and the weight ratio of gadolinium: samarium is 1: 0.3.
To 3.5, the total amount of gadolinium and samarium is 4 to 25% by weight, and the balance is composed of magnesium and inevitable impurities, or contained in such a weight ratio and total amount. In addition to gadolinium and samarium which are prepared, 0.8 to 5% by weight of at least one element selected from the group consisting of calcium, yttrium, scandium and lanthanoids (excluding gadolinium and samarium) is contained. .

The magnesium alloy excellent in room temperature and high temperature strength of the present invention further comprises, if desired, at least one element 2 selected from the group consisting of zirconium and manganese.
It may contain up to wt%.

The magnesium alloy of the present invention which is excellent in room temperature and high temperature strength can be used for casting and manufacturing of die cast parts.

In the magnesium alloy of the present invention, gadolinium and samarium are both effective elements for improving the room temperature and high temperature strength, and the room temperature and high temperature strength of the alloy increase as the amount of addition thereof increases. In the magnesium alloy of the present invention, gadolinium and samarium are added to each other, the addition effect is achieved, a synergistic effect is achieved, and it is considered that the effects of mutually suppressing the necessary element addition amounts are mutually achieved, and thus gadolinium alone is used. With the total addition amount of gadolinium and samarium which is considerably smaller than the case of adding,
That is, when the total addition amount of these is 4% by weight or more, sufficient strength is obtained even at a high temperature up to about 573K. But,
If the total addition amount of them exceeds 25% by weight, the effect is saturated, that is, if the total addition amount of them exceeds 25% by weight, the increase in strength corresponding to the increase of the addition amount cannot be obtained.
It is expensive and therefore technically meaningless. Therefore, in the magnesium alloy of the present invention, the total addition amount of gadolinium and samarium is 4 to 25% by weight, preferably 6 to 12% by weight.

In the magnesium alloy of the present invention, when the weight ratio of [gadolinium / samarium] is larger than [1 / 0.3], the amount of gadolinium becomes relatively large and the amount of expensive gadolinium added decreases. This would deviate from the subject matter of the present invention, which reduces the economic merit. In addition, when the weight ratio of [gadolinium / samarium] is smaller than [1 / 3.5], the amount of gadolinium is relatively small, and a breakthrough of room temperature and high temperature strength obtained by adding gadolinium alone is achieved. Improvement is not achieved. Therefore, in the magnesium alloy of the present invention, the weight ratio of gadolinium: samarium is 1: 0.3-
It is 3.5, preferably 1: 0.7 to 1.3.

In the process of smelting rare earth metals, a mixture of gadolinium and samarium can be obtained in the form of residual europium, which is in high demand from the raw materials of medium heavy rare earths. This mixture also contains rare earth metals other than gadolinium and samarium, but the gadolinium: samarium weight ratio in this mixture is approximately similar to the gadolinium: samarium weight ratio specified in the present invention, and therefore This mixture can be used as it is, or one of gadolinium and samarium can be added to this mixture to adjust the weight ratio of gadolinium: samarium to a desired value. By using this mixture, the production cost of the magnesium alloy of the present invention can be further reduced.

In the magnesium alloy of the present invention, at least one element selected from the group consisting of calcium, yttrium, scandium and lanthanoids (excluding gadolinium and samarium) (eg, neodymium, lanthanum, cerium, mischmetal) is used. The addition makes it possible to further improve the room temperature and high temperature strength of the alloy, and the effect becomes significant when the addition amount is 0.8% by weight or more. However, if the addition amount exceeds 5% by weight, the alloy begins to become brittle, which is not preferable. Therefore, in the magnesium alloy of the present invention, the addition amount of at least one element selected from the group consisting of calcium, yttrium, scandium and lanthanoids (excluding gadolinium and samarium) is 0.8 to 5% by weight, preferably 1 ~ 3% by weight.

Zirconium and / or manganese, which is generally added to the magnesium alloy in an amount of 2% by weight or less, can be effectively used in the magnesium alloy of the present invention.
They are effective in refining the structure and have the effect of improving the strength.

[0015]

【Example】

Examples 1 to 11, Reference Examples 1 to 2 and Comparative Examples 1 to 4 Raw materials were charged and melted in a vacuum melting furnace in an argon atmosphere so that the alloys had the compositions shown in Table 1. Incidentally, misch metal was used as the lanthanoid (excluding gadolinium and samarium), SUS304 material was used as the crucible, and no flux or the like was used. 25 mm of the melt
A test casting was prepared by casting in a mold of × 50 mm × 300 mm. A JIS No. 4 test piece was prepared from the test casting thus obtained. The heat treatment is 500K
10 hours. The following tests were carried out using these test pieces: Tensile test: Crosshead speed 10 mm / min, measuring temperature 300K and 573K, measuring unit of tensile strength = MPa by Instron tensile tester. The measurement results are as shown in Table 1.

[0016]

[Table 1] Composite composition 300K 573K Example No. Gd Sm Zr Mn Mg Other tensile strength Tensile strength Example 1 5 5 0.5-remainder-280 200 Example 2 7 3 0.5-remainder-280 220 Example 3 3 7 0.5 -Remainder -280 180 Example 4 3 3 0.5 -Remainder -260 180 Example 5 12 12 0.5 -Remainder -350 250 Example 6 5 5 -0.5 Remainder -280 210 Example 7 5 5 --Remainder Y: 2 300 220 Example 8 55 --- remaining Sc: 2 295 210 210 Example 9 55 --- remaining Mm: 2 290 215 Example 10 55 --- remaining Ca: 1290 215 Example 11 55 --- remaining-280 190 Comparative Example 1 2 8 0.5 − Remaining − 280 170 Comparative Example 2 1.5 1.5 − − Remaining − 250 120 Comparative Example 3 15 15 0.5 − Remaining − 340 240 Comparative Example 4 5 5 − − Remaining Y: 6 310 210 Comparative Example 5 ----- Remainder -275 90 (AZ91 = Mg-9Al-1Zn-0.6Mn) Comparative Example 6 ----- Remainder -255 176 (WE54 = Mg-5Y-4Nd-0.4Zr)

As is clear from the above Examples 1 to 11 and Comparative Examples 1 to 6, by adding gadolinium and samarium to magnesium in a total amount of 4% by weight or more, remarkable improvements in both room temperature strength and high temperature strength were observed. (Comparison between Examples 1 to 11 and Comparative Example 2), but a total of 25
Even if added in excess of wt%, the effect is saturated and the increase in strength corresponding to the increased amount cannot be obtained (comparison between Example 5 and Comparative Example 3), and the gadolinium: samarium weight ratio is When it is less than 1: 3.5, high temperature strength superior to that of WE54 is not achieved (Comparative Example 1), and further selected from the group consisting of calcium, yttrium, scandium and lanthanoids (excluding gadolinium and samarium). Improvement in both room temperature strength and high temperature strength is seen by adding at least one element 0.8 to 5 wt% (comparison between Examples 7 to 10 and Example 11). Further, zirconium and manganese act equally, are effective for making the structure fine, and have the effect of improving the strength.
Although Comparative Example 4 is excellent in both room temperature and high temperature strength, it is embrittled because the amount of yttrium added exceeds 5% by weight.

[0018]

INDUSTRIAL APPLICABILITY The magnesium alloy of the present invention is superior in room temperature and high temperature strength to the conventional magnesium-alloy alloys containing various kinds of lanthanoids for high temperature, and is light in weight. It is a general-purpose new heat-resistant lightweight magnesium alloy suitable for automobile engine parts that require heat resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kohei Kubota, 1333-2 Ageo City, Saitama Prefecture, Hara City, Saitama Prefecture Mitsui Mining & Smelting Co., Ltd. (72) Inventor Günter Naite Germany Federal Republic of Germany D-6350 Bad Nauheim Mainus Strasse 9 (72) Inventor Eberhard Eschmidt Federal Republic of Germany D-8755 Arsenau Eiinter Frankfurt Igra Wer Strasse 2E

Claims (3)

[Claims] 1. Containing gadolinium and samarium,
The weight ratio of gadolinium: samarium is 1: 0.3-3.
5 and the total amount of gadolinium and samarium is 4 to
A magnesium alloy excellent in room temperature and high temperature strength, characterized in that it is 25% by weight, the balance being magnesium and unavoidable impurities. 2. At least one element selected from the group consisting of calcium, yttrium, scandium and lanthanoids (excluding gadolinium and samarium).
8. Further containing 8 to 5% by weight.
A magnesium alloy having excellent room temperature and high temperature strength as described. 3. The magnesium alloy excellent in room temperature and high temperature strength according to claim 1 or 2, further containing 2% by weight or less of at least one element selected from the group consisting of zirconium and manganese.