JP2741642B2 - High strength magnesium alloy - 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 having excellent strength at room temperature and high temperature, and more particularly to a magnesium alloy having sufficient strength even at a high temperature up to about 473 K required for weight reduction of automobile engine parts and the like. .

[0002]

2. Description of the Related Art In recent years, awareness of global environmental conservation has increased,
The demand for improving the fuel efficiency of automobiles has increased, and the development of lightweight materials for automobiles has been strongly demanded.

[0003] Magnesium alloys have the lowest density among metallic materials currently in practical use, and are expected to be used as lightweight materials for automobiles in the future. At present, the most commonly used magnesium alloy is Mg-Al-Zn-Mn.
System alloy (for example, AZ91 alloy = Mg-9Al-1Zn
-0.5 Mn), and peripheral technologies such as the casting technology of this alloy are in the stage of completion, and this alloy is first studied for weight reduction of automobiles. Further, as a heat-resistant magnesium alloy, an alloy obtained by adding a rare earth element (RE) to magnesium, for example, an Mg-RE-Zr-based alloy has been developed.

[0004]

However, the above-mentioned Mg-Al-Zn-Mn-based alloy has a reduced strength at 393K or more, and is not suitable for applications requiring heat resistance among automobile engine parts. In addition, the heat-resistant Mg-RE-
In a Zr-based alloy, RE is a heavy element, so that RE tends to be biased downward in the molten metal, and addition of Zr used as an essential component is unstable, resulting in an increase in cost.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a novel material suitable for a material for an automobile engine part which requires both heat resistance and room temperature strength. To provide a high strength magnesium alloy.

[0006]

The present inventors have made various studies to solve the above-mentioned problems, and as a result, by adding an appropriate amount of aluminum and an appropriate amount of calcium to magnesium at a predetermined ratio, the room temperature and the temperature are reduced. It has been found that the strength at high temperatures is improved.

It is already known that the strength at room temperature and high temperature is improved by adding calcium to the AZ alloy or the like. However, the amount of calcium added in these cases is generally 0.15% by weight or less, and is merely used to complement the strength of the AZ alloy.
On the other hand, it has been found that the strength at room temperature and high temperature is remarkably improved by setting the addition amount of calcium to 1.4 to 10% by weight and 0.7 times or more of the addition amount of aluminum, and reached the present invention. .

[0008]

That is, the present invention has excellent strength at room temperature and high temperature.
Magnesium alloy contains 2 to 10% by weight of aluminum and
It contains 1.6 to 10% by weight of calcium and has a Ca / Al ratio of
Is not less than 0.7, and 1.6 to 2% by weight of silicon and / or 4% by weight or less of a rare earth element (e.g., yttrium, neodymium, lanthanum, cerium, misch metal) . Combination with 2% by weight or less of zirconium
And the balance consists of magnesium and inevitable impurities.

In the magnesium alloy of the present invention having excellent strength at room temperature and high temperature, aluminum dissolves in magnesium , exhibits age hardening properties, and improves the mechanical properties of the alloy. The effect of adding aluminum increases with the amount of aluminum added, but less than 2% by weight is insufficient, and reaches saturation at 10% by weight. Further, as the amount of aluminum added increases, the elongation of the alloy decreases. Therefore, in the magnesium alloy excellent in room temperature and high temperature strength of the present invention, the amount of aluminum added is set to 2 to 10% by weight, preferably 3 to 9% by weight.

In the magnesium alloy excellent in room temperature and high temperature strength of the present invention, calcium is an element effective for improving high temperature strength. However, the amount of calcium added was 1.4.
When the amount is less than 0.7% by weight or when the ratio of Ca / Al is less than 0.7, the high-temperature strength of the alloy is insufficient. Further, the high-temperature strength is improved as the amount of added calcium is increased, but the cost is increased. Considering cost, there is no merit in adding calcium in excess of 10% by weight. When the Ca / Al ratio is 0.7 or more, the microstructure of the precipitate crystallized in the magnesium alloy changes, and the Mg-Ca compound crystallizes to exhibit excellent high-temperature strength characteristics. Therefore, in the magnesium alloy excellent in room temperature and high temperature strength of the present invention, the amount of added calcium is set to 1.4 to 10% by weight, preferably 2 to 8% by weight, and the ratio of Ca / Al is 0.7 or more, preferably 0.75 or more.

[0012] Zinc, which is generally added to an Mg-Al alloy in an amount of 2% by weight or less, is also effective in the magnesium alloy of the present invention, and has an effect of improving strength. However, if the amount of zinc exceeds 2% by weight, crystallization of the Mg-Al compound occurs, which is not preferable.

In the magnesium alloy excellent in room temperature and high temperature strength of the present invention, the combination of silicon and calcium is extremely effective and has an effect of improving high temperature strength. However, if the addition amount of silicon exceeds 2% by weight, the primary crystal Mg ₂ Si becomes coarse, and the mechanical strength decreases, which is not preferable.

It is known that rare earth elements (eg, yttrium, neodymium, lanthanum, cerium, misch metal) improve the high temperature strength of magnesium alloys,
Recently, especially neodymium and yttrium have been used for magnesium alloys for heat resistance. It was found that this effect was further improved by the combined use with calcium. The improvement of the effect by this combination is saturated at the rare earth element addition amount of 4% by weight.
Considering the cost, there is no merit in adding the rare earth element in excess of 4% by weight.

Examples 1 and 2 and Comparative Examples 1 to 3 Raw materials were charged and melted in a vacuum melting furnace in an argon atmosphere so as to obtain an alloy having the composition shown in Table 1. SUS304 material was used as the crucible, and no flux or the like was used. The molten metal was cast into a 25 mm × 50 mm × 300 mm mold to prepare a test casting. A JIS No. 4 test piece was prepared from the test casting thus obtained. The heat treatment is performed at 500 K for 10 hours. The following tests were carried out using these test pieces: Tensile test: Crosshead speed 10 mm / min using an Instron tensile tester, measuring temperatures 298 K and 473 K, measuring unit of tensile strength = MPa, elongation at break =% Measurement. The measurement results were as shown in Table 1 (% in the table is elongation at break).

[0016]

Table 1 Alloy composition 298K 473K Example No. Al Ca Mg Other tensile strength % Tensile strength % Example 1 3.0 3.0 Remaining Si: 1.8 260 4 190 8 Comparative Example 1 3.0 1.0 Remaining 240 4 110 8 Comparative Example 2 6.0 3.0 Remaining 260 3 120 7 Comparative Example 3 9.0 5.0 Remaining 280 3 130 7

[0017]

The magnesium alloy of the present invention is superior in room temperature and high-temperature strength to conventional general-purpose Mg-Al-Zn-Mn alloys, and is required to be lightweight and heat-resistant. General-purpose heat-resistant lightweight magnesium alloy suitable for

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryuji Ninomiya 1333-2, Hara-shi, Ageo-shi, Saitama Mitsui Kinzoku Mining Co., Ltd. (72) Inventor Kohei Kubota 1333-2, Hara-shi, Ageo-shi, Saitama Mitsui Mining Inside the Research Institute, Inc. (72) Inventor Gunter Naite D-6350 Bad Nauheim Meinusstrasse 9 (72) Inventor Eberhard E. Schmidt D-8755 Arzena U I Unter Frankfurt i Grauer Strasse 2E (56) JP-A-3-90530 (JP, A) JP-A-3-97824 (JP, A) JP-A-3-47941 (JP, A) JP-A-50-115606 (JP, A) JP-A-61 −3863 (JP, A) JP-B 45-2813 (JP, B1)

Claims (2)

(57) [Claims] An aluminum alloy containing 2 to 10% by weight of aluminum and 1.4 to 10% by weight of calcium, a ratio of Ca / Al of 0.7 or more, and further containing 1.6 to 2% by weight of silicon. A magnesium alloy for casting excellent in room temperature and high temperature strength, the balance being composed of magnesium and unavoidable impurities. 2. The composition according to claim 1, wherein the alloy contains 2 to 10% by weight of aluminum and 1.4 to 10% by weight of calcium and has a Ca / Al ratio of 0.7 or more, and further contains 4% by weight or less of a rare earth element.
A magnesium alloy for casting excellent in room temperature and high temperature strength, comprising a combination with zirconium of not more than% by weight and a balance consisting of magnesium and unavoidable impurities.