JPH07122114B2 - High strength magnesium alloy containing gadolinium - Google Patents

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]

Means for Solving the Problems 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. , Also calcium,
Yttrium and lanthanoids (excluding gadolinium)
The inventors have found that the same effect can be obtained even when the amount of gadolinium added is reduced by using at least one element selected from the group consisting of, and have reached the present invention.

That is, the magnesium alloy of the present invention excellent in strength at room temperature and high temperature contains 15 to 25% by weight of gadolinium, or (a) 4 to 15% by weight of gadolinium and (b) calcium, yttrium and lanthanoid ( It is characterized in that it contains 0.8 to 5% by weight of at least one element selected from the group consisting of (excluding gadolinium), and the balance comprises magnesium and inevitable impurities.

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 is an element effective for improving room temperature and high temperature strength, particularly high temperature strength, and the strength increases as the amount of addition thereof increases, and about 1573% by weight of gadolinium is added to about 573K. It has sufficient strength even at high temperatures up to. However, even if it is added in excess of 25% by weight, the increase in strength corresponding to the increase in the added amount cannot be obtained, resulting in high cost.
Therefore, it is technically meaningless. When only gadolinium is used as an alloy component in the magnesium alloy of the present invention, the addition amount is 15 to 25% by weight, preferably 16 to 24% by weight.

In the magnesium alloy of the present invention, calcium, yttrium and lanthanoids (excluding gadolinium) (eg neodymium, lanthanum, cerium,
At least one selected from the group consisting of misch metal)
Even if the addition amount of gadolinium is reduced to 4 to 15 wt% by adding 0.8 to 5 wt% of the seed element, the same effect as when gadolinium is added to 15 to 25 wt% can be obtained, The cost can be reduced. Such an effect becomes significant when the added 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. In the magnesium alloy of such an embodiment, the amount of gadolinium added is 4 to 15% by weight, preferably 5 to 14% by weight, and at least one selected from the group consisting of calcium, yttrium and lanthanoids (excluding gadolinium). The amount of the element added is 0.8 to 5% by weight, preferably 1 to 4% 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.

[0013]

EXAMPLES Examples 1 to 21 and Comparative Examples 1 to 4 Raw materials were charged and melted in a vacuum melting furnace in an argon atmosphere so that alloys having the compositions shown in Table 1 were obtained. Incidentally, misch metal was used as the lanthanoid (excluding gadolinium), SUS304 material was used as the crucible, and no flux or the like was used. The molten metal is 25 mm x 50 mm x 30
A test casting was prepared by casting in a 0 mm die. A JIS No. 4 test piece was prepared from the test casting thus obtained. The heat treatment is 500K for 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.

[0014]

[Table 1] Composite composition 300K 573K Example No. Gd Ca Y Mm Mg Other tensile strength Tensile strength Example 1 16 --- Remaining -340 230 Example 2 24 --- Remaining -360 240 Example 3 20 --- -Remainder Zr: 1 350 235 Example 4 20 --- Remaining Mn: 1 350 234 Example 5 6 1 --- Remainder-330 210 Example 6 6 4 --- Remainder-340 230 Example 7 6 1-Remainder -330 220 Example 8 6-4-Remaining-340 235 Example 9 6--1 Remaining-330 215 Example 10 6--4 Remaining-340 225 Example 11 14 1 --- Remaining-350 235 Example 12 14 4--remaining-360 240 Example 13 14-1-remaining-350 240 Example 14 14-4-remaining-360 245 Example 15 14--1 remaining-350 230 Example 16 14 −− 4 Remaining − 360 235 Example 17 10 2 2− Remaining − 350 230 Example 18 10 2 2 Remaining − 350 225 Example 19 10 − 2 2 Remaining − 350 235 Example 20 10 2 --- Residual Zr: 1 335 235 Example 21 10 2 --- Residual Mn: 1 335 235 Comparative Example 1 10 --- Residual- 310 110 Comparative Example 2 2 2 --- Residual-230 80 Comparative Example 3 --- --- Residual-275 90 (AZ91 = Mg-9Al-1Zn-0.6Mn) Comparative Example 4 ----- Residual-255 176 (WE54 = Mg-5Y-4Nd-0.4Zr)

As is clear from Examples 1 to 21 and Comparative Examples 1 to 4, the addition of 15% by weight or more of gadolinium to magnesium significantly improves both room temperature strength and high temperature strength, particularly high temperature strength. And (b) adding 4-15% by weight of gadolinium and 0.8-5% by weight of at least one element selected from the group consisting of (b) calcium, yttrium and lanthanoids (excluding gadolinium). Thus, both room temperature strength and high temperature strength are improved to the same extent as when gadolinium is added in an amount of 15 to 25% by weight. Although the reason for this has not been clarified yet, gadolinium, calcium, yttrium, and lanthanoids (excluding gadolinium) are all additive elements that improve room temperature strength and high temperature strength. It is presumed that this is due to the fact that the addition effects are overlapped due to the different types of intermetallic compounds used, the synergistic effect is achieved, and the effect of mutually suppressing the necessary element addition amounts is mutually achieved. Further, zirconium and manganese act equally, are effective for making the structure fine, and have the effect of improving the strength.

[0016]

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, Kohei Kubota 1333-2, Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting Co., Ltd. (72) Inventor Gunter Naite D-6350 Bad Nauheim Mainus Strasse 9 (72) Inventor Eberhard Eschmitt, Federal Republic of Germany D-8755 Arsenau Eiunter Frankfurt Iglauwer Strasse 2E (72) Inventor Yo Kojima 1603-1, Kamitomioka-cho, Nagaoka City, Niigata Prefecture (72) Inventor, Sickle Shigeharu Tsuchi 1603-1, Kamitomioka-cho, Nagaoka-shi, Niigata Nagaoka University of Technology

Claims (3)

[Claims] 1. A magnesium alloy having excellent strength at room temperature and high temperature, which contains gadolinium in an amount of 15 to 25% by weight, the balance being magnesium and inevitable impurities. 2. Containing (a) 4 to 15% by weight of gadolinium and (b) 0.8 to 5% by weight of at least one element selected from the group consisting of calcium, yttrium and lanthanoids (excluding gadolinium). A magnesium alloy excellent in strength at room temperature and high temperature, characterized in that the balance consists of magnesium and inevitable impurities. 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.