JPH04147938A - High corrosion resistant magnesium alloy - Google Patents

Abstract

PURPOSE:To obtain an Mg alloy constituted of a uniform phase in which Mg with Ta and Nb of refractory metals enter into solid soln. with each other, excellent in corrosion resistance, wear resistance and toughness and light in weight, at the time of manufacturing the alloy of Mg with Ta and Nb, by adopting a sputtering method. CONSTITUTION:In a chamber 6 of a sputtering apparatus, a substrate 2 made of glass or the like is revolved around a center axis 1 while it is rotated on its own axis. the atmosphere in the chamber 6 is regulated to a gaseous one such as Ar, and a target 4 in which Tas and Nb are embedded in Mg and a target 5 by Ta or Nb are arranged. Then, sputtering is executed to obtain an Mg alloy with a uniform single phase structure having a compn. contg., by atom, 31 to 80% of either Ta or Nb or having a compsn. in which the content of either Ta or Nb is regulated to >=5% and the total content of Ta and Nb is regulated to 20 to 80% can be obtd. on the substrate 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has excellent characteristics such as high corrosion resistance and wear resistance, as well as toughness, and can be used in various industrial and consumer fields including chemical plants. It concerns a new magnesium alloy.

[Prior Art] Magnesium is the lightest practical metal, 1/2 the weight of aluminum and 17'4 the weight of iron, and is the most suitable material for weight reduction. From this point of view, the development of magnesium alloys has focused mainly on strength, and currently Mg-AI series, Mg-Zn series, and Mg-rare earth element series are in practical use. However, magnesium metal or magnesium alloys have poor corrosion resistance and have not been used in corrosive environments.

On the other hand, both Ta and Nb are high melting point metals and do not melt even at the boiling point of Mg. Therefore, it is difficult to obtain an alloy of Ta, Nb, and Mg using a normal method that involves melting.

[Problems to be Solved by the Invention] Ta and Nb are metals with high corrosion resistance, and an alloy obtained by adding Ta or Nb to Mg can be expected to have high corrosion resistance. However, Ta.

Since Nb is both a high melting point metal and does not melt even at the boiling point of Mg, it is difficult to produce an alloy in which these metals are added to Mg using a normal method that involves melting. Successfully producing such an alloy as a homogeneous single-phase alloy rather than a heterogeneous crystalline alloy is expected to result in a new alloy with improved corrosion resistance and unknown properties.

On the other hand, a passive film that can protect metal materials in a mild environment is easily destroyed in a solution containing hydrochloric acid or chlorine ions, which have poor oxidizing power. In particular, hydrochloric acid is highly corrosive, and there are no magnesium alloys that can be used safely, so the current practical magnesium alloys are naturally out of consideration. Therefore, the emergence of a new magnesium alloy that can withstand use in such a corrosive environment where it is extremely difficult to use ordinary magnesium alloys has been expected.

[Means for Solving the Problems] The object of the present invention is to produce alloys containing Ta and Nb, which are difficult to produce using normal melting methods, not as heterogeneous crystalline alloys consisting of multiple phases, but as highly corrosion resistant. The objective is to provide a homogeneous single-phase alloy with sufficient wear resistance and toughness to exhibit the following properties.

Normally, alloys are crystallized in the solid state, but if we apply a method that prevents the formation of long-period regularity in the atomic arrangement during the solid formation process, such as by limiting the alloy composition and solidifying it from the molten state by ultra-rapid cooling, it is possible to crystallize it. An amorphous structure similar to that of a liquid is obtained, and such an alloy is called an amorphous alloy. Also, by using a similar method,
Although it does not have an amorphous structure, it is possible to obtain a non-equilibrium alloy in which the additive elements are supersaturated in solid solution. These amorphous alloys and non-equilibrium alloys are mostly homogeneous single-phase alloys of supersaturated solid solutions, and have significantly higher strength than conventional practical metals, and depending on their composition, have various properties such as unusually high corrosion resistance. shows the characteristics of

As a result of extensive research on the properties of unknown amorphous alloys and non-equilibrium alloys, the present inventors found that A1 and Nb5TaSTi, which are difficult to produce using conventional methods,
It was discovered that an alloy with high-melting point metals such as Zr, Mo, and W could be produced as an amorphous alloy by utilizing a sputtering method that does not require mixing by melting to form the alloy, and the patent application was previously filed. No. 63-51568,
Patent Application No. 83-51567 and Patent Application No. 63-26002
A patent application was filed as No. 0.

As a result of further research, the present inventors found that by using a sputtering method, it was possible to create a uniform single-phase alloy of Mg together with Ta and Nb, and furthermore, that these alloys both contain hydrochloric acid and chloride ions. The present invention was achieved by discovering that the alloy has high corrosion resistance, forming a stable protective film and self-passivating even in harsh corrosive environments such as solutions.

The present invention provides (1) three types of Ta or Nb.
Highly corrosion resistant magnesium alloy containing 1 to 80 atomic % and the remainder substantially consisting of Mg, or (2) containing 5 atomic % or more of either Ta or Nb, with a total of 20 to 80 atomic % of Ta and Nb. It is a highly corrosion-resistant magnesium alloy with the remainder essentially consisting of Mg.

A sputtering method is used to produce the alloy of the present invention.

The sputtering method uses sintering or melting to create a target consisting of multiple crystal phases that have the same average composition as the alloy to be manufactured but is not a single phase, or a metal plate made of the main component of the alloy to be manufactured. It is carried out using a target on which the element to be alloyed is mounted or embedded.

It is difficult to target the Mg-TaXMg-Nb alloy in the present invention by melting, or
Since it is possible to place or embed either or both of a and Nb, the single-phase alloy of the present invention can be obtained by sputtering using such a target. In this case, in order to avoid unevenness in the produced alloy depending on the location, for example, the first
As shown in the figure, a plurality of substrates 2 (one is shown for convenience in the figure) is rotated in a sputtering device chamber 6 around a central axis 1 attached to the chamber 6, and the inner bodies of the substrates 2 also rotate. It is desirable to Then, target 3 is placed along the trajectory of substrate 2.

Furthermore, in order to vary the composition of the produced alloy over a wide range, for example, as shown in FIG. 2, one target 4 is an Mg plate with Ta and/or Nb embedded in it, and the other Target 5 is Ta
and Nb, these two targets 4.5 are tilted with respect to each other, and a substrate 2 that revolves around the central axis 1 and rotates on its own axis is installed near the intersection of the perpendicular lines of the two targets. 2
Two power supplies operate simultaneously while controlling each other's outputs. It is possible to freely change the concentration of alloying elements in the alloy produced by this method. By combining various targets and methods in this way, various highly corrosion-resistant magnesium alloys containing these metal elements can be obtained.

The alloy having the composition of the present invention produced by the sputtering method is a single-phase alloy in which each of the above-mentioned elements is uniformly dissolved in solid solution. The alloy of the present invention, which is a homogeneous solid solution, forms a protective film that is chemically extremely uniform and guarantees high corrosion resistance.

Magnesium is easily attacked by hydrochloric acid, which has poor oxidizing power and is an extremely corrosive environment, or solutions containing chlorine ions, so in order to use magnesium alloys in such environments, it is necessary to have the ability to form a stable protective film. It is necessary to impart this to the magnesium alloy. This is achieved by including the necessary amounts of effective elements. However, in the case of crystalline alloys made by conventional methods such as melting, adding a large amount of various alloying elements often results in a multiphase structure with different chemical properties, and it may not be possible to achieve the desired corrosion resistance. Also, chemical non-uniformity is rather detrimental to corrosion resistance. In contrast, the alloy of the present invention is a homogeneous solid solution and uniformly contains a predetermined amount of effective elements that can form a stable protective film, so it forms a strong and uniform protective film and exhibits sufficiently high corrosion resistance. .

In other words, a magnesium alloy that exhibits corrosion resistance in hydrochloric acid, which has poor oxidizing power and is highly corrosive, and in solutions containing corrosive ions such as chlorine ions, must have a high level of protection that allows a stable protective film to form uniformly on the material. It has the ability to form a film. This is achieved by the alloy composition of the present invention, and the fact that the alloy of the present invention has a single-phase structure in which effective elements are uniformly distributed makes it possible to fabricate alloys with complex compositions as single-phase solid solutions in a supersaturated state. This ensures a uniform protective film.

Next, the reason for limiting the composition of each component in the present invention will be described.

Ta, Nb, and Mg form a single-phase structure over a wide range by using a sputtering method. However, when the number of additive elements is one, it is necessary to contain at least 31 atomic % or more of Ta or Nb in order to exhibit the high corrosion resistance that is the object of the present invention. Further, alloys containing more than 80 atomic % of Ta or Nb change their crystal structure and lose toughness even if they have a single phase structure, so although they have excellent corrosion resistance1, they are not practical.

Therefore, the atomic ratio of Ta or Nb contained in the alloy of the present invention needs to be 31 to 80 atomic %.

However, when adding Ta and Nb in combination, the corrosion resistance is improved compared to when adding either one of them, so in a ternary alloy containing both elements, either Ta or Nb is added to 5
It is sufficient if it contains at least atomic percent and the total amount is at least 20 at%.

[Example] Hereinafter, the present invention will be specifically explained in detail with reference to Examples.

Example 1 An arbitrary number of Ta particles with a diameter of 2011% im-, a diameter lO■■, and a thickness llI are placed on the circumference of a 29m-radius from the center of a Mg disk with a diameter of 1001s and a thickness of 61. Using the apparatus shown in Figure 1 as a target, 1x10-'
A vacuum of ~5 X 10-' Torr is maintained, and a rotating and revolving glass substrate is heated to a temperature of 220 to 280 Torr.
Sputter deposition was performed at an output of W. The compositions of these alloys were analyzed using an X-ray microanalyzer.

As a result of X-ray diffraction, it was confirmed that the resulting alloy was a single-phase alloy. The angle of the strongest line of those X-ray diffraction results (2θ
) and the compositional dependence of the lattice spacing (d) are shown in FIG.

As is clear from the figure, the lattice spacing changes depending on the Ta concentration, and it can be seen that Mg and Ta form a single-phase homogeneous solid solution. However, Ta concentration below 80% and 80%
A clear difference in the lattice spacing was observed between cases where the lattice spacing exceeded 80%, and it was found that alloys with a lattice spacing of more than 80% were brittle and lacked toughness.

Example 2 A T with a diameter of 2011% and a thickness of 11 is placed on the circumference with a radius of 29- from the center on a Mg disk with a diameter of 10011% and a thickness of 6iv.
Using the apparatus shown in Figure 1, we set a target on which four pieces of a were mounted, and kept it in a vacuum of e, ex to''' Torr while flowing Ar at a rate of 5 ml/sin, and it rotated and revolved. Spatter deposition was performed on a glass substrate at a power of 250 W. As a result of X-ray diffraction, the resulting alloy was composed of Mg and Ta, as shown in Example 1.
was confirmed to form a single-phase homogeneous solid solution, and analysis using an X-ray microanalyzer revealed that the composition was a Mg-39 atomic % Ta alloy. This alloy is self-passivated in INMCI solution at 30°C and has a potential I V (SC
The passive current density at E) is also I x 10' A 1vh
2, indicating excellent corrosion resistance.

Example 3 The center of an Mg disk with a diameter of 100s+a and a thickness of 6mm is placed on the circumference of a radius of 29a+ with a diameter of 20mm and a thickness of la+a+.
Using the apparatus shown in Figure 1, Ar was flowed at a rate of 5 ml/sin, and a vacuum of 4X 10' Torr was maintained, and a glass sub-assembly that was rotating and revolving was set as a target. I made a straight scatter deposition with an output of 235W.

As a result of X-ray diffraction, it was confirmed that Mg and Nb formed a single-phase homogeneous solid solution in the resulting alloy, and analysis using an X-ray microanalyzer revealed that the composition was Mg and Nb.
It became clear that it was a -46 atomic % Nb alloy. This alloy is self-passivated in IN MCI solution at 30°C, and has excellent corrosion resistance with a passive current density of 1.2 x 10" A/2 at potential IV (SCE) by potentiodynamic method. It was found that it shows.

Example 4 Radius 2 from the center of a disk with a diameter of 100m5 and a thickness of 6mm
Using the apparatus shown in Fig. 1, a total of 6 pieces of Ta and Nb with a diameter of 20 mm and a thickness of 1 inch were placed alternately on the circumference of a 9si+, and Ar was added at 5 ml/cm using the apparatus shown in Fig. 1.
While flowing at a speed of sin, a vacuum of 4×10'Torr was maintained, and sputter deposition was performed at an output of 270 W on a rotating and revolving glass substrate. As a result of X-ray diffraction, the resulting alloy was composed of Mg, Ta, and N.
It was confirmed that b formed a single-phase homogeneous solid solution,
Also, by analysis using an X-ray microanalyzer,
The composition was revealed to be an alloy of Mg-15 at.% Ta-20 at.% Nb. This alloy has an IN temperature of 30°C.
It is self-passivated in HCI solution, and the passive current density at potential IV (SCE) by potentiodynamic method is also 9.
51X 1O-2A 7m2 It was found that it was small and exhibited excellent corrosion resistance.

Example 5 A Mg disk having the same shape as the Mg target with a diameter of 1100a and a thickness of 6mm was used, with 6 pieces of Ta each having a diameter of 20a+m and a thickness of 1mm embedded on the circumference with a radius of 29a+a from the center. Using the apparatus shown in Figure 2, Ar
5.5X 10' while flowing at a speed of 5il/win
A vacuum of Torr was maintained, and sputter deposition was performed on a rotating and revolving glass substrate with an output of 150 W for the Mg target and an output of 250 W for the embedded target. As a result of X-ray diffraction, it was confirmed that Mg and Ta formed a single-phase homogeneous solid solution in the resulting alloy, and analysis using an X-ray microanalyzer revealed that the composition was Mg - 31 at% Ta. It turned out to be an alloy. This alloy has an I of 30°C
It is self-passivated in N HCI solution, and the passive current density at potential IV (SCE) by potentiodynamic method is also
It was found that the corrosion resistance was as small as 1.4X 1O-IA/1tr2 and exhibited excellent corrosion resistance.

Example 6 Mg alloys shown in Table 1 were produced by combining various targets and using the same methods as those shown in Examples 2 to 5.

Table 1 also shows the results of Examples 2 to 5.

As a result of X-ray diffraction, it was confirmed that these alloys formed a single-phase homogeneous solid solution.

These alloys are self-passivated in IN MCI solution at 30°C, and as shown in Table 1, the passivation current density at the potential I V (SCE) measured by the potentiodynamic method is also small and excellent. It was found that the material exhibited excellent corrosion resistance.

Table 1 Alloy (atomic %) Passive current density (^/i2) Mg-31
Ta 1.4X 10-'Mg-39Ta
1. OX 10-1Mg-44Ta Mg-80Ta Mg-73Ta Mg-10-1 Mg-44Ta %g-46Nb Mg-57Nb Mg-72Nb Mg-8ONb Mg-5Ta-15Nb Mg-10Ta-1ONb Mg-15Ta-2ONb Mg- 27Ta-2ONb Mg-13Ta-32Nb Mg-34Ta-5Nb Mg-44Ta-27Nb Mg-55Ta-25Nb [Effect of the invention] The sium single-phase alloy detailed above is: 9, OX 10-2 5.2X 10- 2 3, lX 10-2 2.8X 10-2 1.7X10'1.2X10" 9, OX 10-2 5.5X 10-2 5, OX 10-2 1, IXLQol 1.0Xlo" 9.5X to -2 8, OX 10-2 9, OX 10-2 7.2X 10-2 5.8X 10-2 2, lX 10-2 An alloy containing Mg as an essential element, which has poor oxidizing power and forms a stable protective film even in highly corrosive hydrochloric acid solutions or corrosive environments containing chlorine ions, has a low corrosion rate, and has a low passive current density. It is a highly corrosion resistant alloy.

[Brief explanation of the drawing]

1 and 2 are schematic views showing an example of a sputtering apparatus for producing the alloy of the present invention, and FIG. 3 is a graph showing the X-ray diffraction results of Example 1. 1... Substrate revolution axis, 2... Autorotating substrate, 3.4.5... Target, 6... Sputter chamber

Claims (2)

[Claims] (1) A highly corrosion-resistant magnesium alloy containing 31 to 80 atomic % of either Ta or Nb, with the remainder substantially consisting of Mg. (2) A highly corrosion-resistant magnesium alloy containing 5 atomic % or more of either Ta or Nb, with a total of 20 to 80 atomic % of Ta and Nb, and the balance substantially consisting of Mg.