JP2002121637A - Magnesium alloy having excellent heat resistance and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnesium alloy in which cast cracking resistance can be secured though the content of aluminum is reduced, and further, heat resistance represented by creep resistance in a high temperature region is improved and to provide its production method. SOLUTION: The magnesium alloy has a composition containing, by weight, 0.6 to 4.6% Nd, further containing rare earth elements mainly consisting of Ce, La and Nd by 1.0 to 7.0% and <=0.8% Al, and the balance magnesium with inevitable impurities. In its production method, a magnesium alloy blended with Misch metal containing rare earth elements essentially consisting of Ce, La and Nd by 1.0 to 7.0%, further additionally blended with 0.8 to 3.0% Nd and also containing <=0.8% Al is formed, and, when the weight % of Nd is defined as W1, and the weight % of rare earth elements including Nd is defined as W2, the value of W1/W2 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnesium alloy having excellent heat resistance and a method for producing the same.

[0002]

2. Description of the Related Art Magnesium alloys have attracted widespread attention in aircraft materials and vehicle materials because of their light weight.
As the magnesium alloy, an Mg-Al alloy, Mg
-Zn-based alloys (AM60, AM50,
AZ91) is the mainstream. Al is added in an amount of about 2 to 10% mainly for the purpose of improving cast cracking resistance and improving strength characteristics at room temperature by solid solution strengthening and crystallized material dispersion strengthening. It is known that these magnesium alloys have excellent die-casting properties, but do not always have sufficient heat resistance, particularly creep resistance. Therefore, Mg-rare earth element alloys are being developed as magnesium alloys having excellent heat resistance. As disclosed in JP-A-3-90530, as a Mg-rare earth element-based alloy, 2 to 11% of Al, 0 to 12% of Zn,
An alloy having a composition containing 1% or less of Mn, 0.5 to 7% of Ca, and 0.1 to 4% of a rare earth element is known.

Further, as a Mg-rare earth element alloy,
As disclosed in JP-A-9-291332, Al is 4.5 to 10% and Mn is 0.3 to 1 by weight ratio.
%, An alloy containing 0.1 to 3% of Ca and 1 to 3% of a rare earth element is known.

Further, as a Mg-rare earth element alloy,
As disclosed in JP-A-7-278717, Al is 1.5 to 10.0% by weight and Ca is 0.2% by weight.
An alloy having a composition containing about 5.5% to 2.5% or less of a rare earth element is known.

[0005] Further, as disclosed in Japanese Patent Application Laid-Open No. 7-11371, a Mg-rare earth element-based alloy has a composition of Mg-Al-Zn-rare earth element, and Al is 1.0-3. There is known a magnesium alloy in which 0%, Zn is set to 0.25 to 3.0%, and rare earth elements are set to 0.5 to 4.0%.

Further, as disclosed in Japanese Patent Application Laid-Open No. 1-107185, the alloy contains 1-10% of Nd or Nd-based metal, the balance is substantially Mg, and the matrix is a β-type silicon nitride whisker. There is known a magnesium alloy for β-type silicon nitride whisker reinforced composite material reinforced with. This is a magnesium alloy for a composite material reinforced with silicon nitride whiskers, although it contains 1-10% neodymium (Nd) or neodymium-based metal, and further contains no cerium or lanthanum. , Which causes the price of magnesium alloy to rise.

As a Mg-rare earth element alloy, as disclosed in JP-A-5-287429,
Al is 1.0 to 4.0%, and Nd is {32 [Al%] ^-2 +
Alloys set at 2.4% or less are known. In the embodiment according to this publication, Al is 0.8 to 9.0%, N
d is set to 1.09 to 4.75%. In this case, since a large amount of Al is contained and only expensive Nd is used as a rare earth element, the price of the magnesium alloy is increased.

[0008]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 3-9
No. 0530, Magnesium alloy disclosed in JP-A-9-2
No. 91332, a magnesium alloy disclosed in
JP-A-278717, magnesium alloy
The magnesium alloy according to -11371 contains Al at a considerable amount of 1.0% or more. JP-A-5-28
No. 7429 also discloses that the magnesium alloy also has an Al content of 0.8.
% Or more. These magnesium alloys
Since Al is contained, the casting crack resistance can be improved, and furthermore, it contributes to the improvement of the strength characteristics at room temperature by solid solution strengthening and crystallization dispersion strengthening.

However, in a magnesium alloy containing a considerable proportion of Al, an Al-rich phase in which Al is dissolved in a supersaturated state tends to be formed. Since the Al-rich phase in which Al is dissolved in supersaturation is thermally unstable,
When used in a high-temperature region, the creep resistance tends to decrease due to the diffusion of Al, and there is a limitation on use in a thermal environment.

[0010] The present invention has been made in view of the above-mentioned circumstances, and it is possible to ensure casting crack resistance regardless of the reduction of aluminum, and to further reduce heat resistance represented by creep resistance in a high temperature region. It is an object to provide an improved magnesium alloy.

Further, the present invention is advantageous for producing a magnesium alloy which can secure casting cracking despite reducing aluminum and has improved heat resistance typified by creep resistance in a high temperature region. An object of the present invention is to provide a method for manufacturing a magnesium alloy.

[0012]

The present inventor has been developing a magnesium alloy having excellent heat resistance based on the above-mentioned problems. As a first feature, a measure is adopted to reduce the amount of aluminum which can contribute to the improvement of the casting crack resistance but tends to lower the creep resistance. As a second feature, a method is adopted in which a rare earth element containing cerium (Ce), lanthanum (La), and neodymium (Nd) as a main component is added while neodymium (Nd) in the above-mentioned rare earth element is additionally added. I have. According to this, despite the reduction of the amount of aluminum that can contribute to the improvement of the casting crack resistance, the casting crack resistance can be ensured, and the heat resistance represented by the creep resistance in a high temperature region is improved. It has been found that an improved magnesium alloy can be provided. The present inventor has developed a magnesium alloy and a method for manufacturing a magnesium alloy according to the present invention based on this finding.

The reasons for obtaining the above-mentioned effects are as follows.
By adding a rare earth element mainly composed of cerium, lanthanum and neodymium, solid solution strengthening of a magnesium alloy can be achieved. Second, a rare earth element mainly composed of cerium, lanthanum and neodymium is combined with magnesium. Thirdly, neodymium is easily dissolved in a magnesium matrix as compared with cerium and lanthanum, and the solid solution can be improved by forming a thermally stable compound (Mg-rare earth element compound). Therefore, it is presumed that increasing the amount of neodymium in the rare earth element effectively contributes to strengthening of magnesium alloy, improvement of heat resistance, and creep resistance.

That is, the magnesium alloy excellent in heat resistance according to the present invention has neodymium (Nd) in a weight ratio of 0.6 to 0.6.
In addition to containing 4.6%, 1.0 to 7.0% of a rare earth element containing cerium (Ce), lanthanum (La), and neodymium (Nd) as main components, and 0.1% of aluminum (Al).
8% or less, with the balance being magnesium and inevitable impurities.

According to the method for producing a magnesium alloy having excellent heat resistance according to the present invention, a magnesium alloy is added in a weight ratio of 10%.
When it is set to 0%, at 100%, cerium (C
e), lanthanum (La), neodymium (Nd) as a main component and a misch metal containing a rare earth element in an amount of 1.0 to 7.
0% and neodymium (Nd) 0.8 to 3.
0% additional blending and 0.8% aluminum (Al)
% Of magnesium alloy containing neodymium (N
When the weight% of d) is W1 and the weight% of the rare earth element containing neodymium (Nd) is W2, the value of W1 / W2 is increased.

[0016]

DETAILED DESCRIPTION OF THE INVENTION Aluminum can contribute to improvement of casting crack resistance and corrosion resistance. However, if Al is excessive,
The thermal diffusion of Al in the supersaturated portion of Al induces a decrease in creep resistance. Considering the above circumstances,
In the magnesium alloy according to the present invention, the weight ratio of aluminum is set to 0.8% or less. Considering the above circumstances, the amount of aluminum is 0.6% or less by weight,
0.5% or less, 0.3% or less, 0.1% or less can be exemplified, and in some cases, 0.08% or less, 0.06% or less.
% Or less, or 0.04% or less.

According to the magnesium alloy having excellent heat resistance according to the present invention, the rare earth element containing cerium, lanthanum, and neodymium as a main component has a solid solution strengthening of magnesium in a matrix and a thermally stable property. Magnesium-
Dispersion strengthening by formation of a rare earth element compound can be achieved, whereby a balance between strength characteristics in a room temperature region and heat resistance in a high temperature region can be achieved.

It is preferable to use a low-cost misch metal as a supply source of the rare earth element. Misch metal is a cerium group and contains cerium, lanthanum, and neodymium as main components. The misch metal generally also contains praseodymium (Pr) as a main component.

If the rare earth element containing cerium, lanthanum, and neodymium as a main component is excessive, the amount of the compound to be crystallized becomes excessive, elongation at room temperature is reduced, and the toughness tends to be remarkably reduced. In view of these circumstances, in the magnesium alloy according to the present invention, the rare earth element containing cerium, lanthanum, and neodymium as main components has a weight ratio of 1.0 to 7.0.
%. Here, the upper limit of the rare earth element containing cerium, lanthanum, and neodymium as main components is 6.2%, 5.8%, and 5.6 depending on the circumstances described above.
%, 5.4%, 5.0%, 4.8%, 4.5%, 4.0
%, Etc., and the lower limit is 1.3%, 1.5%
%, 2.0%, 2.5%, 3.0%, and the like. Therefore, the content of the rare earth element containing cerium, lanthanum, and neodymium as main components is 1.3 to 6.
2% range, 2.0-5.6% range, 2.7-5.0
%, Etc. can be exemplified. Considering the effect of the rare earth element on grain boundary strengthening, the effect of improving casting crack resistance, and the tendency of toughness lowering when excessively added, the content of the above rare earth element is 1.6 to 5.9% by weight, especially 2.3 ~
5.3%, especially 2.8 to 4.8%.

Neodymium is easily dissolved in a magnesium matrix as compared with cerium, lanthanum, etc., and is advantageous in drawing out solid solution strengthening of magnesium, and is typified by strengthening of magnesium alloy, improvement of heat resistance, and creep resistance. It effectively contributes to the heat resistance. However, even if neodymium is excessively added, the improvement effect is saturated and the cost increases.
Therefore, the magnesium alloy according to the present invention contains 0.6 to 4.6% of neodymium. Depending on the use of the magnesium alloy, the upper limit of neodymium is 4.4%, 4.2%, 4.0%.
%, 3.8%, 3.6%, 3.4%, etc., and the lower limit of neodymium is 0.8%, 1.0%, 1.2%.
%, 1.4%, 1.6%, 1.8%, and the like. Taking into account the heat resistance improvement effect of neodymium, the saturation effect of the improvement effect at the time of excessive addition, the cost, etc., the content of neodymium (Nd) is 0.8 to 4.4% by weight,
In particular, it can be 1.0 to 4.0%, especially 1.2 to 3.6%.

In consideration of the above-described improvement effect of neodymium, it is preferable to increase the proportion of neodymium in the rare earth element containing cerium, lanthanum, and neodymium as main components. Therefore, in the magnesium alloy excellent in heat resistance according to the present invention, when the weight% of neodymium itself is W1 and the weight% of rare earth elements including neodymium, cerium and lanthanum is W2, the value of W1 / W2 is 0. .16 or more. Depending on the use of the magnesium alloy, the value of W1 / W2 is, for example, 0.18 or more, 0.20 or more, 0.22 or more, 0.25 or more, 0.25 or more.
27 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, and the like. Taking into account solid solution strengthening by neodymium, grain boundary strengthening by other rare earth elements, and the effect of improving casting crack resistance, the value of W1 / W2 is in the range of 0.16 to 0.8, 0.2
Examples thereof include a range of 0 to 0.60, a range of 0.25 to 0.55, and the like.

According to the method for producing a magnesium alloy having excellent heat resistance according to the present invention, when the magnesium alloy is 100% by weight, cerium (Ce), lanthanum (La), neodymium (100%) are used at 100%. 0.8 to 0.1% of misch metal containing rare earth element whose main component is Nd)
In addition to mixing 7.0%, neodymium (Nd) is 1.0 to 1.0%.
A magnesium alloy containing 3.0% additional blending and containing 0.8% or less of aluminum (Al) is formed, and the weight% of neodymium (Nd) is W1, and the weight% of the rare earth element containing neodymium (Nd) is When W2 is set, the value of W1 / W2 is increased.

The misch metal is cerium, lanthanum,
Contains rare earth elements containing neodymium as a main component. However, since the misch metal is a cerium group, the content of neodymium is limited. Therefore, according to the method of the present invention, in order to increase the proportion of neodymium in the rare earth element, neodymium is supplemented separately by 1.0 to 3.0% in addition to the misch metal. This makes it possible to obtain a magnesium alloy having high heat resistance typified by creep resistance, which cannot be obtained by strengthening only misch metal or is difficult to obtain.

The additional amount of neodymium is selected depending on the use of the magnesium alloy, the target content of neodymium in the misch metal, etc., but is in the range of 1.1 to 2.9%.
1.3 to 2.8% range, 1.5 to 2.5% range,
A range of 1.8 to 2.2% can be exemplified. Neodymium strengthens solid solution, neodymium improves heat resistance,
Taking into account the effect of improving casting crack resistance, the saturation phenomenon of the effect of improvement when excessively added, the cost, and the like, the added amount of neodymium is 1.2 to 2.7% by weight, particularly 1.4 to 2.
3%, in particular, 1.9 to 2.1% can be adopted.

According to the method of the present invention, the value of W1 / W2 can be set to 0.16 or more. Depending on the use of the magnesium alloy, the neodymium content in the misch metal, and the like, the value of W1 / W2 is 0.18 or more, and the value of W1 / W2 is 0.1 to 0.8.
20 or more, 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, and the like. As the range of W1 / W2, the above range can be exemplified.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below together with test examples with reference to the drawings. By melting the starting materials prepared at the mixing ratios shown in Table 1, a molten magnesium alloy was formed, and the molten metal was injected into a cavity of a mold (die), solidified, and solidified. No.
1 to No. 18) was formed. Of these, in Table 1, *
No. marked with 1, No. 4, no. 7 is a comparative example. The others are invention alloys.

In this embodiment, a commercially available misch metal was used as a source of the rare earth element. This misch metal is a cerium group and contains cerium (Ce), lanthanum (La), neodymium (Nd), and praseodymium (Pr) as main components. The proportion in the misch metal used in the present example was about 50% by weight of cerium (Ce),
About 20% lanthanum (La) and about 2 neodymium (Nd)
0% and about 10% praseodymium (Pr). Therefore, the proportion of neodymium (Nd) among the rare earth elements constituting the misch metal is relatively low, that is, 20%.
The rare earth elements constituting the misch metal are affected by the melting yield upon melting.

As shown in Table 1, the magnesium alloy was
When the test example No. was 100%, the test example No. 1
Then, the weight ratio of misch metal (MM in Table 1 and FIG. 5)
1%). Test Example No. In 2,
1% misch metal is blended in weight ratio,
Neodymium (Nd) is added by 1.0%. Test Example No. In No. 3, 1% of misch metal is compounded by weight, and 1.5% of neodymium (Nd) is further compounded. Test Example No. In No. 4, 2% of misch metal is blended by weight. Test Example No. In No. 5, 2% by weight of the misch metal is blended, and 1.0% of neodymium (Nd) is further blended. Test example N
o. In No. 6, the misch metal is blended by 2% by weight and neodymium (Nd) is further blended by 1.5%.

Test Example No. In No. 7, 3% of misch metal is compounded by weight. Test Example No. In No. 8, 3% by weight of misch metal is added, and 1.0% of neodymium (Nd) is added by weight. Test example N
o. In No. 9, 3% by weight of misch metal is added, and 1.5% of neodymium (Nd) is additionally added. Test Example No. In No. 10, the misch metal is compounded by 3% by weight and neodymium (Nd) is further added by 2.0%. Test Example No. In 11,
With 3% misch metal in weight ratio,
Neodymium (Nd) is added 2.5%. Test Example No. In No. 12, the misch metal is compounded by 3% by weight, and neodymium (Nd) is additionally mixed by 3.0%. Test Example No. No. 13 contains 3% by weight of misch metal and also contains neodymium (N
3.5% of d) is added.

Test Example No. In No. 14, 4% of misch metal is blended by weight. Test Example No. In 15,
4.0% by weight of misch metal and 1.0% of neodymium (Nd) are added.
Test Example No. For 16, the ratio of misch metal is 4% by weight
While being blended, 1.5% of neodymium (Nd) is further blended.

Test Example No. No. 17 contains 5.0% by weight of misch metal and also contains neodymium (N
d) is added 1.0%. Test Example No. 18
In this example, 5% of misch metal is blended in weight ratio, and 1.5% of neodymium (Nd) is further blended.

The compositions of the alloys of the test examples (No. 1 to No. 18) were analyzed. The results of the analysis, that is, the amounts of aluminum, cerium, lanthanum, neodymium, and praseodymium are shown in Table 1. Indicated. According to Table 1, the inventive alloys (Test Examples No. 2, No. 3, No. 5, No. 6, N
o. 8 to No. In 18), neodymium is 0.1% by weight.
The content of rare earth elements containing cerium, lanthanum, and neodymium as main components is specified within a range of 1.0 to 7.0%, and aluminum is specified within a range of 6 to 4.6%. It is specified to be 0.8% or less, especially 0.06% or less.

In other words, in the alloy of the present invention, the aluminum content was 0.06% or less, and the cerium, lanthanum, neodymium, and praseodymium increased as the mixing ratio of the misch metal increased.

[0034]

[Table 1]

[0035]

[Table 2]

An axial force holding characteristic evaluation test was performed for each test example. In this case, as shown in FIG. 2, a sleeve-shaped test piece 1 is prepared, and a first contact plate 11 and a second contact plate 12 are prepared.
And a bolt 14 (shaft length: M) having a head 13 and a nut 15, and the shaft portion 14 a of the bolt 14 is
And the nut 15 is fastened to the male screw portion of the shaft portion 14 a of the bolt 14 while being inserted through the insertion hole of the second contact plate 12. Then, the creep resistance was evaluated by obtaining the axial force retention (%) based on the following equation. In this case, the initial axial force was set to 64 MPa, and the axial force retention was measured after holding for 300 hours in a high temperature region (150 ° C.).

Axial force retention (%) = ｛(LF-LO) /
(L1−LO)｝ × 100 LO: length of bolt before fastening L1: length of bolt after fastening LF: length of bolt after fastening and after test FIG. 1 and Table 2. The horizontal axis in FIG. 1 shows the blending state in the test example, and the vertical axis shows the axial force retention (%). As can be understood from FIG. 1 and Table 2, Test Example N in which the content of misch metal was 1%.
o. 1 (Comparative Example) had an axial force retention of 62.15%. However, in addition to 1% misch metal, 1.0% neodymium
% Of test example No. 2 means that the axial force retention rate is 7
It was 4.99%. Further, in Test Example No. 1 containing 1.5% neodymium in addition to 1% misch metal. 3
Had an axial force retention of 72.58%.

Further, in Test Example No. 2 containing 2% of misch metal. 4 (comparative example) had an axial force retention of 63.16%.
Met. However, in Test Example No. 1 containing 1.0% neodymium in addition to 2% misch metal. Sample No. 5 had an axial force retention of 78.71%. In addition, 2% misch metal
Test Example N containing 1.5% additional neodymium in addition to
o. Sample No. 6 had an axial force retention of 74.42%.

Further, as can be seen from Table 2 and FIG. 1, Test Example No. 3 containing 3% of misch metal was used. In No. 7 (Comparative Example), the axial force retention was 64.39%. However, in Test Example No. 1 containing 1.0% neodymium in addition to 3% misch metal. In No. 8, the axial force retention was 75.6%. In addition, neodymium was added in addition to 3% of misch metal.
Test Example No. 5% additionally blended. In No. 9, the axial force retention was 83.47%. Test Example No. 2 containing 2.0% neodymium in addition to 3% misch metal. 10 is
The axial force retention was 87.3%. 3% misch metal
Test Example N containing 2.5% neodymium in addition to N
o. No. 11 had an axial force retention of 83.85%. Test Example No. No. 3 containing neodymium 3.0% in addition to misch metal 3%. No. 12 had an axial force retention of 84.12%. 3.5% neodymium in addition to 3% misch metal
In Test Example No. 13 has an axial force retention of 8
It was 4.92%.

Further, as can be understood from FIG. 1, Test Example No. 4 containing 4% of misch metal was used. No. 14 had an axial force retention of 71.33%. But Misch Metal 4
Test Example N containing 1.0% neodymium in addition to 0.1%
o. In No. 15, the axial force retention was 84.48%. Further, Test Example No. No. 1 containing 1.5% neodymium in addition to 4% misch metal. No. 16 has an axial force retention of 83.
47%. Test Example No. 1 containing neodymium 1.0% in addition to misch metal 5% In No. 17, the axial force retention was 79.2%. Test Example No. 5 containing 1.5% neodymium in addition to 5% misch metal. 18
Had an axial force retention of 82.93%.

As described above, the addition of the misch metal and the additional addition of neodymium are effective in improving the axial force retention. In other words, it is effective for improving the creep resistance.

That is, if a rare earth element such as cerium, lanthanum, neodymium, and praseodymium is contained in a magnesium alloy and the proportion of neodymium in the rare earth element is increased, the cost is reduced and the creep resistance is typified. Heat resistance can be improved, and thus the above-mentioned axial force retention can be increased. However, as the amount of additional neodymium increases, the effect of the additional neodymium tends to saturate, and also causes an increase in cost.

With respect to the representative alloys among the above-mentioned invention alloys, proof stress (MPa: stress value at which a permanent set of 0.2% is generated), tensile strength (MPa), elongation (%), and hardness were measured. Table 2 shows the test results. The hardness was Vickers hardness and the applied load was 5 kgf (about 50 N). Table 2
According to the report, as neodymium increases, the yield strength, tensile strength and hardness tend to increase, but the effect tends to be saturated.

Further, the weight% of neodymium itself is W1,
The weight% of the rare earth element including cerium, lanthanum, and neodymium is W2. Table 2 shows each test example (No. 1 to No. 2).
18) shows the value of W2 and the value of W1 / W2. As shown in Table 2, the alloys of the invention (No. 1 to No. 18)
No. 1, No. 4, no. 7), W2
Was in the range of 1.0 to 6.0%, and the value of W1 / W2 was 0.16 or more.

Further, Table 2 shows the ratio of (neodymium content / cerium content) contained in the magnesium alloy, that is, Nd /
The value of Ce is also shown. As shown in Table 2, in the alloy of the invention, Nd
The value of / Ce was 0.3 or more, especially 1.0 or more, 2.0 or more, and 2.6 or more.

The horizontal axis in FIG. 3 shows the test time (hr) maintained in a high temperature region (150 ° C.), and the vertical axis in FIG. 3 shows the axial force retention (%). In this case, the magnesium alloy used was Test Example No. 9 (Mg-3% MM-
1.5% Nd). As a comparative example, AZ91D (9
% Al-1% Zn) magnesium alloy, AS21
(2% Al-1% Si), and a magnesium alloy (Mg-Al-Zn-rare earth element) according to JP-A-7-11371 described in the prior art,
An axial force holding characteristic evaluation test was performed in the same manner. The test results of the comparative example are also shown in FIG. As can be understood from FIG. In No. 9, no significant change was observed in the axial force retention even when the test time was prolonged. On the other hand, in the magnesium alloy disclosed in Japanese Patent Application Laid-Open No. Hei 7-11371, the creep resistance was not sufficient. Therefore, when the test time was prolonged, the axial force retention gradually decreased. Magnesium alloy according to AS21 containing Si, AZ9 containing Zn
Since the magnesium alloy according to 1D also has insufficient creep resistance, when the test time is prolonged, the axial force retention rate further decreased.

A casting crack test was also performed. In this case, the magnesium alloy used is an inventive alloy.
o. 9 (Mg-3% MM-1.5% Nd). In the casting crack test, as shown in FIG. 4, a mold 22 having a cavity 21 having a predetermined constraint length M is used, and a molten magnesium alloy 26 charged in a pressurizing chamber 25 communicating with the cavity 21 is plunged. The mold was loaded into the cavity 21 of the mold 22 and solidified by the forward operation 24. In a central region of the cavity 21, a heat insulating material 29 for delaying solidification is arranged. The conditions of the casting crack test are as follows.

Casting machine: Hard mold casting machine Mold: I-beam mold Plunger speed: 0.65 m / sec Injection pressure: 64 MPa Injection temperature: Melting point of magnesium alloy + 20 ° C. Relationship between casting crack test result and axial force retention Is shown in FIG. The horizontal axis in FIG. 5 shows the length of restraint of the occurrence of casting cracks (mm), and the vertical axis in FIG. 5 shows the axial force retention (%). The constraint length of casting crack occurrence means the constraint length M when casting cracks occur, in other words, means that casting cracks did not occur up to this length. Therefore, the longer the value of the constraint length of casting crack occurrence, the better the casting crack resistance.

As a comparative example, AE42 (4% Al-2%
AM60B, a magnesium alloy related to misch metal)
(6% Al-0.5% Mn) magnesium alloy,
The magnesium alloy (Mg-Al-Mn-Ca-rare earth element) according to JP-A-9-291332 described in the prior art, and the magnesium alloy (Mg-Al-) according to JP-A-7-11371 described in the prior art. Using Zn-rare earth elements), a casting crack test was performed in the same manner.

As shown in FIG. 5, the invention alloy (Test Example N)
o. In 9), AE42, AM60B, and JP-A-9-29
The axial force retention was much higher than the magnesium alloys disclosed in JP-A-1332 and JP-A-7-1137. In addition, in the invention alloy (Test Example No. 9), although the casting crack occurrence restraint length is superior to the magnesium alloy according to JP-A-9-291332, AE4
2. AM60B, slightly smaller than the magnesium alloy according to JP-A-7-1137. As described above, in the invention alloy (Test Example No. 9), although the aluminum effective for improving the casting cracking resistance is considerably reduced to 0.06% or less, the practically effective casting cracking resistance is reduced. Secured. It is presumed that the reason for this is that in the invention alloy (Test Example No. 9), the strength in the high-temperature region is secured, so that the casting crack resistance is secured.

It should be noted that the inventive alloy has improved creep resistance and is therefore suitable for manufacturing components used in thermal environments. Examples of such parts include engine parts of a vehicle and parts around the engine.

(Others) The present invention is not limited to the embodiment described above and shown in the drawings, but can be implemented with appropriate modifications without departing from the scope of the invention. Weight ratios can be replaced by weight ratios, and weight percents can be replaced by weight percents. The description of the names appearing in the entire text of the specification is merely an example, and even a part thereof can be described in the claims. In the present specification, the column of the embodiment of the invention, the column of the example, the numbers described in each table are described in each claim as an upper limit or a lower limit of each element, and as an upper limit or a lower limit of each physical property value. You can do it.

(Supplementary Note) The following technical idea can be understood from the above description. When α (weight% of neodymium / weight% of cerium) in the magnesium alloy is α, α is 0.7 or more, 1.0 or more, 1.2 or more, 1.4 or more, 1.6 or more, 1.8 or more. , 2.0 or more, 2.2 or more, the magnesium alloy excellent in heat resistance according to each of the claims, and a method for producing the same. The heat-resistant magnesium according to any one of claims 1 to 3, wherein α is set to 1.0 to 3.0, where (wt% of neodymium / wt% of cerium) in the magnesium alloy is α. Alloys and manufacturing method thereof. -The magnesium alloy excellent in heat resistance according to each of the claims, wherein the rare earth element is cerium, lanthanum, neodymium, or praseodymium, and a method for producing the same. -The magnesium alloy excellent in heat resistance described in each claim used for casting, and a manufacturing method thereof. -The magnesium alloy excellent in heat resistance according to any one of claims to be used for die casting, and a method for producing the same. A rare earth element does not contain yttrium, a magnesium alloy excellent in heat resistance according to each claim,
And its manufacturing method. 2. The magnesium alloy having excellent heat resistance according to claim 1, wherein the source of the rare earth element is misch metal. 3. -0.6 to 4.6% by weight of neodymium (Nd) itself
And cerium (Ce), lanthanum (L
a), a rare earth element containing 1.0 to 7.0% of a rare earth element containing neodymium (Nd) as a main component, 0.8% or less of aluminum (Al), and a balance of magnesium and inevitable impurities. The source of the alloy is misch metal, a magnesium alloy with excellent heat resistance. -When the magnesium alloy is 100% by weight,
At 100%, cerium (Ce), lanthanum (L
a), 1.0 to 7.0% of a misch metal containing a rare earth element containing neodymium (Nd) as a main component, and 0.8 to 3.0% of neodymium (Nd) is further added;
Further, a magnesium alloy containing 0.8% or less of aluminum (Al) is formed, and the weight% of neodymium (Nd) is changed to W1.
And the weight% of the rare earth element containing neodymium (Nd) is W
A magnesium alloy excellent in heat resistance, wherein the value of W1 / W2 is increased when the ratio is 2. -When the magnesium alloy is 100% by weight,
At 100%, cerium (Ce), lanthanum (L
a), 1.0 to 7.0% of a misch metal containing a rare earth element containing neodymium (Nd) as a main component, and 0.8 to 3.0% of neodymium (Nd) is further added;
A magnesium alloy containing 0.8% or less of aluminum (Al) and having excellent heat resistance. In addition to containing 0.6 to 4.6% of neodymium (Nd) by weight, cerium (Ce), lanthanum (La),
A rare earth element containing neodymium (Nd) as a main component is 1.0
A magnesium alloy excellent in creep resistance, characterized by having a composition of not more than 7.0% and 0.8% or less of aluminum (Al), with the balance being magnesium and inevitable impurities. -When the magnesium alloy is 100% by weight,
At 100%, cerium (Ce), lanthanum (L
a), 1.0 to 7.0% of a misch metal containing a rare earth element containing neodymium (Nd) as a main component, and 0.8 to 3.0% of neodymium (Nd) is further added;
Further, a magnesium alloy containing 0.8% or less of aluminum (Al) is formed, and the weight% of neodymium (Nd) is changed to W1.
And the weight% of the rare earth element containing neodymium (Nd) is W
2. A method for producing a magnesium alloy having excellent creep resistance, wherein the value of W1 / W2 is increased when 2. When held at 150 ° C. for 300 hours in the atmosphere,
A magnesium alloy excellent in heat resistance, wherein the reduction in the axial force retention is 10% or less or 5% or less. -A magnesium alloy excellent in casting crack resistance and heat resistance described in each claim or a method for producing the same. The method for producing a magnesium alloy excellent in heat resistance according to claim 5, wherein the magnesium alloy according to claim 1 is produced. -Thermal environment parts formed of the magnesium alloy according to each claim. -A thermal environment die-cast component made of the magnesium alloy according to each claim. -Engine parts and engine parts formed of the magnesium alloy according to the claims.

[0054]

According to the magnesium alloy according to the present invention, casting crack resistance can be ensured despite reduction of aluminum, and heat resistance represented by creep resistance in a high temperature region is improved. be able to.

According to the manufacturing method of the present invention, the casting crack resistance can be ensured despite the reduced amount of aluminum, and neodymium is additionally compounded while using misch metal which is advantageous in cost. W1 /
The value of W2 can be increased, thereby improving heat resistance represented by creep resistance in a high temperature region. That is, the method for producing a magnesium alloy according to the present invention is suitable for producing the magnesium alloy according to the present invention.

[Brief description of the drawings]

FIG. 1 is a graph showing a test result of an axial force retention.

FIG. 2 is a conceptual diagram of a test jig used in an axial force holding characteristic test.

FIG. 3 is a graph showing a relationship between a holding time and an axial force holding ratio in a high temperature region (150 ° C.).

FIG. 4 is a conceptual diagram of a test device used in a casting crack test.

FIG. 5 is a graph showing a relationship between casting crack resistance and axial force retention.

[Explanation of symbols]

In the figure, 14 is a bolt, 15 is a nut, and 22 is a mold.

Continued on the front page (72) Inventor Toshio Horie 41 Toyota Chuo Research Institute Co., Ltd.

Claims (7)

[Claims] 1. Neodymium (Nd) is added in a weight ratio of 0.6 to
In addition to containing 4.6%, 1.0 to 7.0% of a rare earth element containing cerium (Ce), lanthanum (La), and neodymium (Nd) as main components, and 0.1% of aluminum (Al).
A magnesium alloy having excellent heat resistance, characterized by having a composition containing 8% or less, with the balance being magnesium and inevitable impurities. 2. A magnesium alloy excellent in heat resistance according to claim 1, wherein aluminum (Al) is 0.5% or less by weight. 3. The method according to claim 1, wherein the weight percent of neodymium (Nd) is W1, cerium (Ce),
When the weight% of the rare earth element containing lanthanum (La) and neodymium (Nd) is W2, the value of W1 / W2 is 0.16.
A magnesium alloy excellent in heat resistance characterized by being set as described above. 4. The method according to claim 1, wherein W1 / W2
Is set to 0.30 or more, the magnesium alloy having excellent heat resistance. 5. Assuming that a magnesium alloy is 100% by weight, a misch metal containing a rare earth element containing cerium (Ce), lanthanum (La), and neodymium (Nd) as main components in 100% is used. 0-7.0%, neodymium (Nd) is added 0.8-3.0%, and a magnesium alloy containing 0.8% or less of aluminum (Al) is formed. Neodymium (Nd) Of the cerium (C
e) A method for producing a magnesium alloy having excellent heat resistance, wherein the value of W1 / W2 is increased when the weight percentage of rare earth elements including lanthanum (La) and neodymium (Nd) is W2. 6. The method according to claim 5, wherein the value of W1 / W2 is set to 0.
A method for producing a magnesium alloy having excellent heat resistance, wherein the number is set to 16 or more. 7. The method according to claim 6, wherein the value of W1 / W2 is set to 0.
A method for producing a magnesium alloy having excellent heat resistance, wherein the magnesium alloy is set to 30 or more.