JPH0472043A - Highly corrosion resistant magnesium alloy - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance in a magnesium alloy by adding Ni and Cu as well as La, Ce, Nd or the like to an Al-contg. Mg allay and specifying its compsn. and the volumetric fraction of an amorphous phase in its metallic structure. CONSTITUTION:This Mg alloy is a one contg., by atom, 37 to 88% Mg, 5 to 35% of one or more kinds of Ni and Cu, 5 to 25% of one or more kinds among La, Ce, Nd, Y, Sm, Mm (misch metal) and Ca, 2 to 45% Al and Mg having the content more than that of Al and in which the volumetric fraction Vf of an amorphous phase in the metallic structure is regulated to >=50%. By the function of Ni and Cu as well as La, Ce, Ca or the like, the metallic structure is formed into an amorphous phase one having corrosion resistance or a mixed phase one of amorphous and crystalline phases. Moreover, in the surface of the alloy, Al itself or intermetallic compounds constituted of Al with La, Ce, Nd, Y, Sm and Mm form oxides functioning as a passive film.

Description

[Detailed description of the invention] A0 Purpose of invention (1) Industrial application fields The present invention relates to highly corrosion resistant magnesium alloys.

(2) Prior Art Conventionally, as this type of corrosion-resistant magnesium alloy, one containing Af and manufactured by applying a rapid solidification method is known (see Japanese Patent Laid-Open No. 83446/1983).

(3) Problems to be solved by the invention However,
In conventional magnesium alloys, some improvements in corrosion resistance have been observed due to the inclusion of Al and the refinement of the crystalline phase.11 Corrosion resistance is still insufficient in severe corrosive environments, and for example, high corrosion resistance is required. It is unsuitable as a constituent material for automobile engine cylinder blocks, various cases, parts that come into contact with cooling water, etc.

In view of the above, the present invention further improves corrosion resistance by making the metal structure an amorphous phase structure, a mixed phase structure of an amorphous phase and a crystalline phase, or a crystalline phase structure, and by containing a specific amount of Al. An object of the present invention is to provide the above-mentioned magnesium alloy.

B0 Structure of the Invention (1) Means for Solving the Problems The highly corrosion-resistant magnesium alloy according to the present invention has an Mg content a of 37 at%≦a≦88 at%, and contains at least one of Ni and Cu. The amount is 5 atomic%
≦b≦35 at%, and the content C of at least one selected from La, Ce, Nd, Y, Sm, Mm (Mitshu Metal) and Ca is 5 at%≦c≦25 at%, Af content d
is 2 atomic %≦d≦45 atomic %, the relationship between the Mg content a and the A2 content d is a≧d, and the volume fraction Vf of the amorphous phase in the metal structure is 50 atomic %.
% or more.

Furthermore, the highly corrosion-resistant magnesium alloy according to the present invention has an Mg content a of 37 at%≦a≦85 at%, and a content of at least one of Ni and Cu of 5 at%.
≦b≦25 atomic %, and the content C of at least one selected from La, Ce, Nd, Y, Sm, Mm (Mitshu Metal) and Ca
is 5 at%≦c≦25 at%, the Al content d is 2 at%≦d≦43 at%, the Si content e is 3 at%≦e≦10 at%, and Mg The relationship between the content a of AP and the content d of AP is a≧d, and the volume fraction Vf of the amorphous phase in the metal structure is 50
% or more is the second feature.

Furthermore, a third feature is that at least the surface layer portion of the alloy is composed of a crystalline phase produced by a phase change of an amorphous phase.

Furthermore, the above-mentioned No. 1. Although it has the same composition as the magnesium alloy mentioned in the second feature, the fourth feature is that the metal structure is changed to a crystalline phase resulting from a phase change from an amorphous phase. This is the fifth feature.

(2) Effect According to the first feature, Ni, Cu and La, Ce, N
Depending on the functions of d, Y, Sm, Mm, and Ca, the metal structure of the magnesium alloy becomes an amorphous phase structure or a mixed structure of an amorphous phase and a crystalline phase, and these structures have corrosion resistance. In particular, Ca has a high ability to refine the metal structure and is effective in improving the corrosion resistance of magnesium alloys.

Also, on the alloy surface, Al itself or Ai! .

An intermetallic compound consisting of La, Ce, Nd, Y, Sm, and Mm combines with oxygen to form an oxide, and the oxide functions as a passive film.

Due to these factors, magnesium alloy exhibits high corrosion resistance.

The contents of Ni and Cu, as well as La and Ce
, Nd, Y, Sm, Mm, and Ca content C outside the above range, the metal structure as described above cannot be obtained.

Further, when the Aj2 content d is d<2 atomic %, it becomes difficult to form the passive film, while when d>45 atomic %, the corrosion resistance of the magnesium alloy is impaired and the strength is reduced.

According to the second feature, in addition to the above, St improves the hardness of the metal structure, and St also exhibits an amorphous phase forming function and a passive film forming function, so that the corrosion resistance of the magnesium alloy is further improved. do.

In this case, the content of Ni and Cu is La.

The reasons for limiting the content C of Ce, Nd, Y, Sm, Mm, and Ca and the content d of AP are the same as described above.

Further, if the Si content e is e<3 atomic %, the hardness-improving effect, amorphous phase forming effect, and passive film forming effect cannot be obtained, while if e>10 atomic %, the corrosion resistance is impaired.

In the third feature, the crystalline phase generated by the phase change of the amorphous phase becomes an extremely fine metal structure, and the anticorrosion effect of the passive film is also obtained, so that the corrosion resistance of the magnesium alloy is improved.

Along with such crystallization, Ni and C are added to the Mg matrix.
It is known that the corrosion resistance of Mg alloys is extremely reduced when transition elements such as u are included, but in the present invention, a passive film is formed on the alloy surface due to the Al content. , the above-mentioned problem will not occur.

4th. According to the fifth feature, the same effect as described in the third feature can be obtained.

When hot plastic working such as forging or extrusion is performed using an amorphous Mg alloy as a material, the metal structure in the product tends to become a crystalline structure due to the relatively low crystallization temperature Tx of the alloy. However, even in such a case, the fourth. According to the fifth feature, the corrosion resistance of the product can be improved.

(3) Example Mg6SN i HCe as a magnesium alloy with Mg as the main chemical component, at least one selected from Ni and Cu, at least one selected from La, Ce, Nd, Y, Sm, Mm and Ca, and Al roA
An example amorphous Mg alloy having a composition of l + e (values are in atomic %) was produced. The amorphous Mg alloy of this example has an amorphous phase volume fraction Vf of approximately 100% and a hardness Hv of 282.

The amorphous Mg alloy of the example was manufactured by applying a single roll rapid solidification method. That is, in manufacturing, 20
A method was adopted in which the molten alloy was spouted by argon gas pressure from a spout with a diameter of 1 mm in a quartz crucible onto a copper cooling roll with a diameter of 25 mm rotating at a rotational speed of 0 Orp-.

The same method was also applied to MgysNi+5Cel.

A comparative amorphous Mg alloy having a composition (values are atomic %) was produced. The volume fraction Vf of the amorphous phase of this comparative example amorphous Mg alloy is approximately 100%, and its hardness Hv is 268
It is.

Figure 1 shows an example amorphous Mg alloy and a comparative example amorphous Mg alloy.
In Figure 0 showing the corrosion test results of the alloy, the line x1 corresponds to the example amorphous Mg alloy, and the line x2 corresponds to the comparative example amorphous Mg alloy.

The corrosion test method is as follows.

Corrosion of magnesium alloys is likely to occur in aqueous solutions containing chloride ions, sulfate ions, etc. Therefore, magnesium alloys are usually subjected to salt spray tests and the like.

However, considering the application of magnesium alloys to engine cylinder blocks, etc., the salt spray test requires relatively low test conditions because it measures the amount of corrosion in a low-temperature range where there is insufficient contact between the metal and the electrolyte. There are problems such as it being too lenient and the test time being short.

Therefore, in this example, each test piece was
% salt aqueous solution, 90±2℃, air blowing (0.5℃)
~1 j! Corrosion resistance was quantitatively measured by conducting a test in which the progress of corrosion was accelerated in a short period of time under severe conditions (2000/5h) and determining the corrosion loss per unit area with respect to the immersion time.

As is clear from the line X, the example amorphous Mg alloy is A
1. Due to the inclusion of , it hardly corroded in the above test and therefore has excellent corrosion resistance. On the other hand, the comparative amorphous Mg alloy shown by line X showed a tendency to increase in weight as the immersion time progressed, and this was due to the formation of brittle oxides on the alloy surface.

FIG. 2 shows the results of a corrosion test of an example crystalline Mg alloy, etc., in which the example amorphous Mg alloy was crystallized and the volume fraction Vf of the crystalline phase was approximately 100%. Same as above.

In the figure, the line y corresponds to the example crystalline Mg alloy, and the line y corresponds to the comparative example crystalline Mg alloy obtained by crystallizing the comparative example amorphous Mg alloy. Also line y.

corresponds to the crystalline/1 alloy represented by JIS AC2B. Furthermore, the point Zl is Mg□N i,,Ce,.

Af,. Point 22 is Mg
In a crystalline Mg alloy having a composition of ysN j +sCe +o (values are atomic %) and crystallized during the manufacturing stage, point Z is crystal 1 expressed by ASTM AZ91.
Each corresponds to tMg alloy.

As is clear from the line yI, the example crystalline Mg alloy is A
Due to the inclusion of l1, the immersion time in the test was approximately 10
It hardly corrodes until it reaches 00 hours, so it has excellent corrosion resistance, and this is the crystalline Al shown by the line y3.
Better than alloy.

Other various Mg alloys have inferior corrosion resistance compared to the crystalline A1 alloy shown by line y.

Table 1-XI shows the composition, metal structure, hardness, and corrosion resistance of various magnesium alloys. The method of manufacturing these magnesium alloys and the corrosion tests for them are the same as described above.

In the metallographic structure, a means an amorphous phase structure, and C means a crystalline phase structure, so a+C means a mixed structure. In terms of corrosion resistance, it has better corrosion resistance than the crystalline A1 alloy specified by JIS AC2B.
Bad ones are marked with an "○" mark, and bad ones are marked with an "x" mark.

Examples of Mg-N1-R,E, (Ce)-AI2 alloys are shown in Table I. Here, RoE means a rare earth element, and the same applies hereinafter.

Table ■ Table ■ In Table H, alloy 02) corresponds to the example of the present invention, and alloy 03) corresponds to the comparative example.

Mg-N1-R, E, (La, Nd, Mm, Y or S
m) Examples of the present invention regarding -Af alloys are shown in Table (2).

In Table I, alloys (1) to (8) correspond to examples of the present invention, and alloys (9) to OD correspond to comparative examples.

Mg-Cu-R,E, (Ce)-Aj! Examples of the present invention related to alloys are shown in Table (2).

table ■ Mg 1-Cu Rl E.

(La+Ce) Examples of the present invention regarding Al-based alloys are shown in Table 2.

table ■ Mg-Ni-R.

E.

(Ce+Nd) -Al system Examples of alloys are shown in Table ■.

table ■ In table ■, Alloy (28) corresponds to the embodiment of the present invention g Ca-AI! Zero-fire related to alloys Examples are shown in Table 3.

table ■ Mg-N1-Cu R6 E.

(Ce) f Examples of alloys are shown in Table V.

table ■ In table ■, Alloy (25) corresponds to the embodiment of the present invention I won, Alloy (26) also corresponds to a comparative example.

death, Alloy (29) also corresponds to a comparative example.

Mg-Ni R, E, (Ce+Mm)-Aj2 system combination Examples of the present invention relating to gold are shown in Table 2.

table ■ Mg R1 E.

(Ce) Ca Aj2 series Examples of the present invention regarding alloys are shown in Table 2.

table ■ Mg Ni-R.

E.

(Ce) f Si-based Examples of alloys are shown in Table X.

Table X In Table X, alloys (32) to (35) correspond to examples of the present invention, and alloy (36) corresponds to a comparative example. The composition of Alloy (35) is the same as Alloy (33), but its metal structure is a crystalline phase resulting from a phase change of an amorphous phase.

Examples of the present invention regarding Mg-Ni-R,E, (Mm)-Af-3i series alloys are shown in Table XIO.

1st. FIG. 2 is a graph showing the results of corrosion tests on magnesium alloys.

Claims (5)

[Claims] (1) Mg content a is 37 at%≦a≦88 at%, and content b of at least one of Ni and Cu is 5 at%
≦b≦35 atomic%, La, Ce, Nd, Y, Sm, Mm (misch metal)
and the content c of at least one selected from Ca is 5 at%≦c≦25 at%, and the content d of Al is 2
atomic %≦d≦45 atomic %, the relationship between the Mg content a and the Al content d is a≧d, and the volume fraction Vf of the amorphous phase in the metal structure is 50
% or more. (2) Mg content a is 37 at%≦a≦85 at%, and content b of at least one of Ni and Cu is 5 at%
≦b≦25 atomic%, La, Ce, Nd, Y, Sm, Mm (misch metal)
and the content c of at least one selected from Ca is 5 at%≦c≦25 at%, and the content d of Al is 2
atomic%≦d≦43 atomic%, the Si content e is 3 atomic%≦e≦10 atomic%, and the relationship between the Mg content a and the Al content d is a≧d. , the volume fraction Vf of the amorphous phase in the metal structure is 50
% or more. (3) The highly corrosion-resistant magnesium alloy according to item (1) or item (2), wherein at least the surface layer portion is composed of a crystalline phase generated by a phase change of an amorphous phase. (4) Mg content a is 37 at%≦a≦88 at%, and content b of at least one of Ni and Cu is 5 at%
≦b≦35 atomic%, La, Ce, Nd, Y, Sm, Mm (misch metal)
and the content c of at least one selected from Ca is 5 at%≦c≦25 at%, and the content d of Al is 2
atomic%≦d≦45 atomic%, the relationship between the Mg content a and the Al content d is a≧d, and the metal structure is a crystalline phase resulting from a phase change of an amorphous phase. A highly corrosion resistant magnesium alloy. (5) Mg content a is 37 at%≦a≦85 at%, and content b of at least one of Ni and Cu is 5 at%
≦b≦25 atomic%, La, Ce, Nd, Y, Sm, Mm (misch metal)
and the content c of at least one selected from Ca is 5 at%≦c≦25 at%, and the content d of Al is 2
atomic%≦d≦43 atomic%, the Si content e is 3 atomic%≦e≦10 atomic%, and the relationship between the Mg content a and the Al content d is a≧d. , a highly corrosion-resistant magnesium alloy whose metal structure is a crystalline phase produced by a phase change of an amorphous phase.