KR100360530B1 - Ni based amorphous alloy compositions - Google Patents

Abstract

The present invention relates to a nickel-based amorphous alloy composition. The composition of these alloys is nickel-zirconium-titanium-silicon quaternary alloy, the composition range is 45-63 atomic% nickel, 32-48 atomic% zirconium + titanium, 1-11 atomic% silicon, and general formula Ni _a ( Zr _lx Ti _x ) _b Si _c , which may be represented by at least one element of V, Cr, Mn, Cu, Co, W, Sn, Mo, Y, C, B, P, Al (M). ) Is disclosed an alloy composition is added 2-15 atomic% to the total composition.

The nickel-based bulk amorphous alloy of the present invention has excellent amorphous forming ability and can be produced by a casting method with a thickness of 1 mm or more. In addition, it has a supercooled liquid zone of 50K or more to enable high temperature molding using viscous flow at the temperature of the subcooled liquid zone, and the nickel-based bulk amorphous alloy of the present invention has high strength, abrasion resistance, and corrosion resistance, and thus high strength wear resistant parts, Structural materials, welding and coating materials and the like can be made of amorphous alloy in the bulk form.

Description

Nickel-based amorphous alloy compositions

The present invention relates to a nickel-based amorphous alloy composition, more specifically, the supercooled liquid region (supercooled) of 20K or more when cooled to a temperature below the glass transition temperature (glass transition temperature) at a cooling rate of 10 ⁶ K / s or less from the liquid phase A nickel-based amorphous alloy composition in which an amorphous having a liquid region is formed.

Most metal alloys form crystal phases whose order of atoms is solidified from the liquid phase. However, if the cooling rate during solidification is sufficiently above the threshold value to limit the nucleation and growth of the crystal phase, the irregular atomic structure of the liquid phase can be maintained as it is. Such alloys are commonly referred to as amorphous alloys or metallic glass.

Since the first amorphous phase was reported in Au-Si based alloys in 1960, many kinds of amorphous alloys have been invented and utilized. However, since most amorphous alloys undergo rapid nucleation and growth of the crystal phase in the supercooled liquid phase, a very high cooling rate is required to prevent the formation of the crystal phase upon cooling from the liquid phase. Therefore, most amorphous alloys were manufactured using rapid quenching techniques with very high cooling rates of 10 ⁴ -10 ⁶ K / s, ribbons with a thickness of less than about 80 µm, diameters of less than about 150 µm It was possible to produce only in the form of fine lines or powders of several hundred μm or less in diameter. Such amorphous alloys produced by rapid solidification have limited form and size, so their practical applications have been very limited. Therefore, in order to utilize an amorphous alloy as a commercial metal material, it has been required to develop an alloy having an excellent amorphous forming ability with a low critical cooling rate that can avoid formation of a crystal phase upon cooling from a liquid phase.

If the alloy has excellent amorphous forming ability, it is possible to produce a bulk amorphous alloy by the casting method. For example, for the preparation of bulk amorphous alloys having a thickness of about 1 mm, crystallization should not occur even at low cooling rates of 10 ³ K / s or less. For the production of bulk amorphous alloys, not only low cooling rate but also having a large subcooled liquid region is very important from an industrial point of view, because of the viscous flow in the subcooled liquid region, the formation of the bulk amorphous alloy is possible. This is because it is possible to manufacture parts of a certain type.

According to US Pat. Nos. 5,288,344, 5,735,975 and the like, a zirconium-based bulk amorphous alloy having excellent amorphous forming ability has been developed with a critical cooling rate of several K / s for forming an amorphous alloy. In addition, since the zirconium-based bulk amorphous alloy has a very large supercooled liquid region, it may be molded into a certain shape and used as a structural material. Indeed, Zr-Ti-Cu-Ni-Be and Zr-Ti-Al-Ni-Cu alloys, etc., specified in the patent, are already utilized as bulk amorphous products.

However, due to problems such as high reactivity, resource limitation, impurity content, and price of the zirconium metal, there is still a need to develop an alloy containing a more thermodynamically stable metal such as nickel as a major element of industrial and economic utility. Has been required.

Nickel-based amorphous alloys have a very good corrosion resistance and strength from the research on amorphous ribbons produced by the rapid solidification method, which shows that they have very advantageous advantages as structural materials if they can only be made from bulk materials. have. Papers Materials Transactions, JIM, Vol. 40, no. 10, pp. According to 1130-1136, a bulk amorphous alloy having a maximum diameter of 1 mm was obtained in a Ni-Nb-Cr-Mo-P-B system by copper mold casting, and has a relatively large supercooled liquid region.

However, in order to manufacture and industrially use the nickel-based bulk amorphous alloy by the casting method, it is necessary to develop an alloy having a larger supercooled liquid region and excellent amorphous forming ability. Furthermore, the conventional nickel-based alloy contains a large amount of phosphorus (P) and boron (B), which are disadvantageous in the manufacture of the alloy, thereby limiting its commercialization. For example, due to the high vapor pressure of phosphorus, there is a problem that a special method must be used to add a large amount of phosphorus to the alloy. Therefore, the casting method is superior to conventional nickel-based amorphous alloys, and the development of a new nickel-based bulk amorphous alloy containing no element such as phosphorus having a high vapor pressure is urgently required.

Accordingly, it is an object of the present invention to provide a new nickel-based bulk amorphous alloy composition which can be manufactured by a casting method, which is superior to conventional nickel-based amorphous alloys, and which does not contain elements such as phosphorous having a high vapor pressure.

1 is a quasi-ternary composition diagram showing a composition range of a nickel-zirconium-titanium-silicon alloy.

In order to achieve the above object, according to the present invention, the general formula Ni _a (Zr _lx Ti _x ) _b Si _c (where a, b, c are atomic% of nickel, zirconium + titanium, silicon, respectively) , 45 atomic% ≤ a ≤ 63 atomic%, 32 atomic% ≤ b ≤ 48 atomic%, 1 atomic% ≤ c ≤ 11 atomic%, and x has a value of 0.4 ≤ x ≤ 0.6). An amorphous alloy composition is provided.

Preferably, the nickel-based amorphous alloy composition of the present invention comprises 44 atomic% ≤ a ≤ 55 atomic%, 39 atomic% ≤ b ≤ 47 atomic%, 5 atomic% ≤ c ≤ 11 atomic%, or 56 atomic% ≤ a ≤ It is possible to form a bulk amorphous alloy having a thickness of 1 mm or more with a composition satisfying 61 atomic%, 35 atomic% ≤ b ≤ 40 atomic%, and 2 atomic% ≤ c ≤ 7 atomic%. In the design, 1) polyatomic alloy composition of three or more elements should be formed, 2) the difference in size of mutual atomic radius should be 10% or more, and 3) an amorphous alloy composed of elements with large mutual binding energy between atoms. Based on the empirical principle of forming ability, a ternary alloy of Ni (atomic radius: 1.24 kPa) -Ti (atomic radius: 1.47 kPa) -Zr (atomic radius: 1.60 kPa) was used as the base alloy system. The amorphous alloy composition according to the present invention was improved by adding Si, which is known as an amorphous forming ability improving element, to the base alloy system. The amorphous alloy composition according to the present invention was applied to the whole composition to improve the amorphous forming ability and to secure a large subcooled liquid region of 20 K or more. Ni is 45 to 63 atomic% and Zr + Ti is limited to 32 to 48 atomic%. On the other hand, the addition amount of Si according to the present invention is preferably 1 to 11 atomic% based on the total composition, and the amount is 1 atomic. If it is less than%, it is difficult to expect sufficient amorphous forming ability, and even when it exceeds 11 atomic%, it is confirmed that the amorphous forming ability tends to decrease, which is not preferable.

In addition, at least one element (M) of V, Cr, Mn, Cu, Co, W, Sn, Mo, Y, C, B, P, and Al in the alloy composition is contained in an amount of 2 to 15 atomic% based on the total composition. An added nickel-based amorphous alloy composition is provided.

Preferably, the M is Sn and 2 atomic% ≤ M ≤ 5 atomic%, characterized in that the formation of a bulk amorphous alloy having a thickness of 1 mm or more.

Preferably M is in the range of Mo or Y and 3 atomic% ≤ M ≤ 5 atomic%, characterized in that the formation of a bulk amorphous alloy with a thickness of 1mm or more.

The amorphous alloy according to the present invention is characterized in that it can be produced by a rapid solidification method, a mold casting method, a high pressure casting method and the like, and preferably the present invention is characterized in that the amorphous alloy can be produced by an atomizing method. On the other hand, the present invention is characterized in that it is excellent in high temperature workability, and can produce an amorphous alloy through forging, rolling, drawing or other processing.

Preferably, it is possible to produce a composite material based on an amorphous phase and containing a second phase in nm or in μm.

Of the present invention, nickel-based amorphous alloy is 10 ⁶ K / s or rather far under low cooling rate and the liquid is completely solidified in an amorphous phase, 773K or more glass transition temperature (T _g), more than 20K supercooled liquid region (ΔT = crystallization temperature ( T _x ) -glass transition temperature (T _g )). Particularly, in the composition of the alloy described in the present invention, it is possible to manufacture a bulk amorphous alloy having a diameter of 1 mm or more by the copper mold casting method, and has a glass transition temperature of 823K or more and a supercooled liquid region of 50K or more. It contains a composition having a minimum content of elements such as phosphorus, boron, etc., which are technically and economically difficult in the production of the alloy.

The composition range of the nickel-zirconium-titanium-silicon alloy according to the present invention is shown in the quasi-ternary composition diagram of FIG. 1. In the ternary composition diagram of FIG. 1, nickel, (zirconium + titanium), and silicon are represented, and the ratio of zirconium and titanium is 0.6-0.4: 0.4-0.6 as shown in the above equation.

The composition region shown in FIG. 1 is a composition region in which amorphous is formed from the liquid phase at a cooling rate of 10 ⁶ K / s or less, and the supercooled liquid region is ²⁰ K or more. Among the above compositions, in particular 44 atomic% ≤ a ≤ 55 atomic%, 39 atomic% ≤ b ≤ 47 atomic%, 5 atomic% ≤ c ≤ 11 atomic%, or 56 atomic% ≤ a ≤ 61 atomic%, 35 atomic% ≤ b In the composition range of ≤ 40 atomic% and 2 atomic% ≤ c ≤ 7 atomic%, the formation of a bulk amorphous alloy with a diameter of 1 mm or more at a cooling rate of about 10 ³ K / s or less with a glass transition temperature of 823 K or more and a subcooled liquid region of 50 K or more This is possible. This composition area is shown as a hatched area in FIG.

On the other hand, in the alloy composition according to the present invention, at least one element (M) of V, Cr, Mn, Cu, Co, W, Sn, Mo, Y, C, B, P, Al is 2 to the total composition. An alloy composition with 15 atomic percent addition is provided, wherein the alloy composition in this composition range forms amorphous from the liquid phase at a cooling rate of about 10 ⁶ K / s or less and has a supercooled liquid region of ²⁰ K or more. Particularly when M is Sn and 2 atomic% ≤ M ≤ 5 atomic%, the supercooled liquid region is 50 K or more, and a bulk amorphous alloy having a diameter of 1 mm or more can be formed at a cooling rate of about 10 ³ K / s or less. . Also in this composition, especially when M is Mo or Y and 3 atomic% ≤ M ≤ 5 atomic%, the formation of a bulk amorphous alloy having a diameter of 1 mm or more at a cooling rate of about 10 ³ K / s or less with a supercooled liquid region of 60 K or more This is possible.

The nickel-based bulk amorphous alloy of the present invention has excellent amorphous forming ability and can be produced by various kinds of rapid solidification methods such as single roll melt spinning, twin roll melt spinning, and gas atomization. Alloys of some of the alloy compositions of the present invention may be made into bulk amorphous alloys at cooling rates of 10 ³ K / s or less. Examples of the method for producing the bulk amorphous alloy include a die casting method and a molten metal forging method.

In view of the above, according to the present invention, it is possible to obtain a very large supercooled liquid zone of 50 K or more and to ensure excellent workability, and thus to form a plate, rod, or other bulk amorphous alloy by a casting method, and then to form a viscous flow in the supercooled liquid zone. There is an advantage that can be easily molded into a specific type of part using. In addition, after preparing the amorphous powder of the nickel-based amorphous alloy of the present invention by the atomizing method, the preform of the powder can be molded into a bulk amorphous part while maintaining the amorphous structure by applying a high pressure at a high temperature in a supercooled liquid region. Do.

Example 1

Alloys of each composition given in Table 1 were prepared by the arc melting method, melted in a quartz tube, and then sprayed onto a copper wheel rotating at 3200 rpm through a nozzle of approximately 1 mm diameter to a thickness of about 50 μm. Made of an alloy in the form of a ribbon. Thus, the sample manufactured by the single-roll melt spinning method confirmed that it was an amorphous phase by the appearance of the halo form diffraction peak as a result of X-ray diffraction analysis. The glass transition temperature, crystallization temperature and the amount of exothermic enthalpy during crystallization were measured by differential thermal analysis, and the results are shown in Table 1. In addition, the supercooled liquid crystal region was determined from the glass transition temperature and the crystallization temperature, and is shown in Table 1 together.

In general, the larger the subcooled liquid region, the lower the critical cooling rate for amorphous formation. In addition, the larger the supercooled liquid region, the easier it is to form a high temperature using the viscous flow of the amorphous alloy. Of the alloys of Table 1, alloys having a subcooled liquid region of 70 K or above deserve particular attention in this respect.

Sample Number Alloy composition Tg (℃) Tx (℃) △ T ΔH (J / g) One Ni ₅₁ Zr ₂₀ Ti ₂₆ Si ₃ 522.9 548.4 25.5 68.1 2 Ni ₅₃ Zr ₂₀ Ti ₂₄ Si ₃ 530.6 556.6 26 74 3 Ni ₅₅ Zr ₂₀ Ti ₂₂ Si ₃ 542.5 581.9 39.4 70.7 4 Ni ₅₉ Zr ₂₀ Ti ₁₈ Si ₃ 556.5 608.8 52.3 63.2 5 Ni ₆₁ Zr ₂₀ Ti ₁₆ Si ₃ 568.7 613.4 44.7 51 6 Ni ₆₃ Zr ₂₀ Ti ₁₄ Si ₃ 575.7 607.4 31.7 42.6 7 Ni ₅₁ Zr ₂₀ Ti ₂₄ Si ₅ 536.7 576.7 40 85.4 8 Ni ₅₃ Zr ₂₀ Ti ₂₂ Si ₅ 546.2 592.4 46.2 72.9 9 Ni ₅₅ Zr ₂₀ Ti ₂₀ Si ₅ 557.7 602.4 44.7 59.2 10 Ni ₅₉ Zr ₂₀ Ti ₁₆ Si ₅ 569.4 624.5 55.1 39.5 11 Ni ₆₁ Zr ₂₀ Ti ₁₄ Si ₅ 576.6 620.5 43.9 39.2 12 Ni ₅₁ Zr ₂₀ Ti ₂₂ Si ₇ 558.5 608.6 50.1 60.6 13 Ni ₅₃ Zr ₂₀ Ti ₂₀ Si ₇ 563.5 613 49.5 68.8 14 Ni ₅₅ Zr ₂₀ Ti ₁₈ Si ₇ 568.9 617.1 48.2 60.1 15 Ni ₅₁ Zr ₂₀ Ti ₂₀ Si ₉ 570.3 617.2 46.9 67.9

Example 2

The alloy of each composition given in Table 2 was prepared by the arc melting method, and then dissolved in a quartz tube, and then a copper mold having a cavity of 1-5 mm in diameter and 50 m in length through a nozzle of about 1 mm diameter. Was injected into the bulk amorphous alloy having a diameter of 1-5mm, length of 45-50mm. As a result of performing X-ray diffraction analysis, the sample prepared by the copper mold casting method was confirmed to be an amorphous phase by the appearance of a halo diffraction peak. The glass transition temperature, crystallization temperature and the amount of exothermic enthalpy during crystallization were measured by differential thermal analysis, and the results are shown in Table 2. In addition, the supercooled liquid crystal region was determined from the glass transition temperature and the crystallization temperature, and is shown in Table 2 together.

Sample Number Alloy composition Tg (K) Tx (K) ΔT (K) ΔH (J / g) One Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ V ₃ 605.63 572.113 33.517 -32.252 2 Ni ₅₇ Zr ₂₀ Ti ₁₂ Si ₅ V ₆ 603.888 559.736 44.152 -20.341 3 Ni ₅₇ Zr ₂₀ Ti ₉ Si ₅ V ₉ 4 Ni ₅₇ Zr ₂₀ Ti ₃ Si ₅ V ₁₅ 5 Ni ₅₇ Zr ₂₀ Ti ₁₈ Si ₃ V ₂ 601.817 566.482 35.335 -57.156 6 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ Cr ₃ 593.205 546.087 47.118 -21.462 7 Ni ₅₇ Zr ₂₀ Ti ₁₂ Si ₅ Cr ₆ 8 Ni ₅₇ Zr ₂₀ Ti ₉ Si ₅ Cr ₉ 9 Ni ₅₇ Zr ₂₀ Ti ₃ Si ₅ Cr ₁₅ 10 Ni ₅₇ Zr ₂₀ Ti ₁₈ Si ₃ Cr ₂ 11 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ Mn ₃ 601.558 564.608 36.95 -31.42 12 Ni ₅₇ Zr ₂₀ Ti ₁₂ Si ₅ Mn ₆ 587.519 553.793 33.726 -29.02 13 Ni ₅₇ Zr ₂₀ Ti ₉ Si ₅ Mn ₉ 14 Ni ₅₇ Zr ₂₀ Ti ₃ Si ₅ Mn ₁₅ 15 Ni ₅₇ Zr ₂₀ Ti ₁₈ Si ₃ Mn ₂ 599.738 553.859 45.879 -60.33 16 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ Cu ₃ 621.598 580.649 40.949 -36.027 17 Ni ₅₇ Zr ₂₀ Ti ₁₂ Si ₅ Cu ₆ 600.272 577.105 23.167 -59.115 18 Ni ₅₇ Zr ₂₀ Ti ₉ Si ₅ Cu ₉ 19 Ni ₅₇ Zr ₂₀ Ti ₃ Si ₅ Cu ₁₅ 20 Ni ₅₇ Zr ₂₀ Ti ₁₈ Si ₃ Cu ₂ 605.495 557.974 47.521 -58.824 21 Ni ₅₇ Zr ₂₀ Ti ₁₈ Si ₃ Co ₂ 610.684 569.363 41.321 -52.642 22 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ Co ₃ 619.456 578.863 40.593 -40.034 23 Ni ₅₇ Zr ₂₀ Ti ₁₂ Si ₅ Co ₆ 24 Ni ₅₇ Zr ₂₀ Ti ₉ Si ₅ Co ₉ 25 Ni ₅₇ Zr ₂₀ Ti ₁₈ Si ₃ W ₂ 607.958 566.878 41.08 -61.962 26 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ W ₃ 625.844 577.724 48.12 -39.033 27 Ni57Zr20Ti ₁₂ Si ₅ W ₆ 625.399 585.526 39.873 -36.004 28 Ni ₅₇ Zr ₂₀ Ti ₉ Si ₅ W ₉ 29 Ni ₅₇ Zr ₂₀ Ti ₁₈ Si ₃ Sn ₂ 623.552 569.459 54.093 -60.087 30 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ Sn ₃ 639.25 588.111 51.139 -49.758 31 Ni ₅₇ Zr ₂₀ Ti ₁₂ Si ₅ Sn ₆ 633.478 587.634 45.844 -44.176

Sample Number Alloy composition Tg (K) Tx (K) ΔT (K) ΔH (J / g) 32 Ni ₅₇ Zr ₂₀ Ti ₉ Si ₅ Sn ₉ 33 Ni ₅₇ Zr ₂₀ Ti ₁₈ Si ₃ Mo ₂ 603.849 560.935 42.914 -47.374 34 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ Mo ₃ 614.086 549.524 64.562 -27.236 35 Ni ₅₇ Zr ₂₀ Ti ₁₂ Si ₅ Mo ₆ 36 Ni ₅₇ Zr ₂₀ Ti ₉ Si ₅ Mo ₉ 37 Ni ₅₇ Zr ₂₀ Ti ₁₈ Si ₃ Y ₂ 565.129 531.714 33.415 -68.547 38 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ Y ₃ 601.766 541.546 60.22 -62.216 39 Ni ₅₇ Zr ₂₀ Ti ₁₂ Si ₅ Y ₆ 40 Ni ₅₇ Zr ₂₀ Ti ₉ Si ₅ Y ₉ 537.92 492.645 45.275 -46.748 41 Ni ₅₇ Zr ₂₀ Ti _17.5 Si ₅ C _0.5 625.221 581.28 43.941 -56.447 42 Ni ₅₇ Zr ₂₀ Ti ₁₇ Si ₅ C ₁ 624.85 588.809 36.041 -38.445 43 Ni ₅₇ Zr ₂₀ Ti ₁₆ Si ₃ C ₂ 617.498 590.138 27.36 -31.775 44 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ C ₃ 45 Ni ₅₇ Zr ₂₀ Ti _17.5 Si ₅ B _0.5 621.154 578.478 42.676 -57.979 46 Ni ₅₇ Zr ₂₀ Ti ₁₇ Si ₅ B ₁ 620.616 575.491 45.125 -61.945 47 Ni ₅₇ Zr ₂₀ Ti ₁₆ Si ₅ B ₂ 617.019 577.481 39.538 -65.567 48 Ni ₅₇ Zr ₂₀ Ti ₁₅ Si ₅ B ₃ 618.959 580.417 38.542 -73.549 49 Ni ₅₇ Zr ₂₀ Ti ₁₃ Si ₅ P ₅ 50 Ni ₅₇ Zr ₂₀ Ti ₈ Si ₅ P ₁₀ 51 Ni ₅₇ Zr ₂₀ Ti ₃ Si ₅ P ₁₅ 52 Ni ₅₇ Zr ₂₀ Ti ₃ Si ₅ P ₁₅ 53 Ni ₅₇ Zr ₂₀ Ti ₁₃ Si ₅ Al ₅ 618.322 578.008 40.314 -48.453 54 Ni ₅₇ Zr ₂₀ Ti ₈ Si ₅ Al ₁₀ 55 Ni ₅₇ Zr ₂₀ Ti ₃ Si ₅ Al ₁₅ 56 Ni ₅₇ Zr ₂₀ Ti ₃ Si ₅ Al ₁₅

As described above, since the nickel-based amorphous alloy composition of the present invention has high strength, wear resistance, and corrosion resistance, the nickel-based amorphous alloy composition may be manufactured and used as a bulk amorphous alloy in high strength wear resistant parts, structural materials, welding and coating materials, and the like.

Claims (6)

General formula Ni _a (Zr _lx Ti _x ) _b Si _c (where a, b, c denote atomic% of nickel, zirconium + titanium and silicon, respectively, 45 atomic% ≤ a ≤ 63 atomic%, 32 atomic A nickel-based amorphous alloy composition which can be represented by% ≤b≤48 atomic%, 1 atomic% ≤c≤11 atomic%, and x has a value of 0.4≤x≤0.6. The nickel-based amorphous alloy composition of claim 1, wherein the alloy composition is 44 atomic% ≤ a ≤ 55 atomic%, 39 atomic% ≤ b ≤ 47 atomic%, and 5 atomic% ≤ c ≤ 11 atomic%. The nickel-based amorphous alloy composition of claim 1, wherein the alloy composition is 56 atomic% ≤ a ≤ 61 atomic%, 35 atomic% ≤ b ≤ 40 atomic%, and 2 atomic% ≤ c ≤ 7 atomic%. The alloy composition according to claim 1, 2 or 3, wherein at least one element (M) of V, Cr, Mn, Cu, Co, W, Sn, Mo, Y, C, B, P, Al is added to the alloy composition. Nickel-based amorphous alloy composition, characterized in that added to 15 atomic%. 5. The nickel-based amorphous alloy composition according to claim 4, wherein M is Sn and 2 atomic% < M < 5 atomic%. 5. The nickel-based amorphous alloy composition according to claim 4, wherein M is Mo or Y and 3 atomic%? M? 5 atomic%.