HIGH STRENGTH, HEAT RESISTANT ALUMINUM-BASED ALLOYS

Abstract: The present invention provides high strength, heat resistant aluminum-based alloys having a composition represented by the general formula Al a M b Ce c , wherein M is at least one metal element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu and Nb; and a, b and c are atomic percentages falling within the following ranges: 50 ≦ a ≦ 93, 0.5 ≦ b ≦ 35 and 0.5 ≦ c ≦ 25, the aluminum alloy containing at least 50% by volume of amorphous phase. The aluminium-based alloys are especially useful as high strength, high heat resistant materials in various applications and since they exhibit superplasticity in the vicinity of their crystallization temperature, they can be easily processed into various bulk materials by extrusion, press woring or hot-forging at the temperatures within the range of the crystallization temperature ± 100°C.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to aluminum-based alloys having a desired combination of properties of high hardness, high strength, high wear-resistance and high heat-resistance. 2. Description of the Prior Art As conventional aluminum-based alloys, there have been known various types of aluminum-based alloys, such as Al-Cu, Al-Si, Al-Mg, Al-Cu-Si, Al-Cu-Mg, Al-Zn-Mg alloys, etc. These aluminum-based alloys have been extensively used in a wide variety of applications, such as structural materials for aircrafts, cars, ships or the like; outer building materials, sash, roof, etc; structural materials for marine apparatuses and nuclear reactors, etc., according to their properties. The conventional aluminum-based alloys generally have a low hardness and a low heat resistance. Recently, attempts have been made to impart a fine-structure to aluminum-based alloys by rapidly solidifying the alloys and thereby improve the mechanical properties, such as strength, and chemical properties, such as corrosion resistance. However, the rapidly solidified aluminum-based alloys known up to now are still unsatisfactory in strength, heat resistance, etc. Rapidly solidified Al-alloys of the claimed type are already known in the art. For instance document EP-A-0 136 508 (1) discloses a high strength aluminum alloy having a general formula Al bal Fe a X b , wherein X is at least one selected from the group consisting of Zn, Co, Ni, Cr, Mo, V, Zr, Ti, Y, Si and Ce; a is from 7 to 15 wt%, b is 1.5 to 10 wt%, the alloy being prepared by rapidly solidifying a molten alloy at a cooling rate of 10⁶ °C/s or higher. The object of this reference (1) is to improve the strength and ductility by forming a microeutectic microstructure in the alloy by rapid-cooling solidification from the molten state. WO-A- 8 606 748 (2) discloses a method of treating alloys containing metastable featureless regions by heating the alloys for transforming the regions at least sufficiently out of their metastable state to improve toughness. The featureless regions are crystalline (refer to page 2, line 15 to page 5, line 13) and, as specific examples, the method is applied to rapidly solidified alloys represented by the general formula Al bal Fe a X b , wherein X is a rare earth metal (preferably Ce), a is from 4 to 12 wt.% and b is from 1 to 8 wt%. DE-A-3 524 276 (3) discloses Ce-containing alloys of, in weight percentage, Al-9Fe-2.5Cu-1.5Mg-1Ni-4Ce, Al-8Ni-4Ce and Al-2/7Cu-0.1/2.OMg-2/12Me-1/6Ce (wherein Me = Fe, Mo, Co and/or Ni). These alloys are prepared by rapidly cooling at a cooling rate of the order of 10⁶°C/s and solidifying melts thereof. The prior art rapidly-solidified alloys have a crystalline microstructure having phases of intermetallic compounds and are improved in their mechanical properties. "J. Mat. Sci", Vol. 22, No. 1, pp. 202-206 (1987) (4) discloses, in weight percentage, Al-8Fe and Al-8Fe-4RE (wherein RE is Ce, Er, Nd or Gd) and these alloys are improved in their strength and stability due to their fine crystalline microstructure formed by rapid-cooling solidification. SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide novel aluminum-based alloys having an advantageous combination of high strength and superior heat-resistance at relatively low cost. Another object of the present invention is to provide aluminum-based alloys which have high hardness and high wear-resistance properties and which can be subjected to extrusion, press working, a large degree of bending, etc. According to the present invention, there are provided aluminum-based alloys having high strength and heat resistance, the aluminum-based alloys having a composition represented by the general formula: Al a M b Ce c wherein: M is at least one metal element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu and Nb; and a, b and c are atomic percentages falling within the following ranges: 50 ≦ a ≦ 93, 0.5 ≦ b ≦ 35 and 0.5 ≦ c ≦ 25, the aluminum-based alloys containing at least 50% by volume of amorphous phase. In the general formula, Ce element may be replaced by a misch metal and the same effects can be obtained. The aluminum-based alloys of the present invention are useful as high hardness materials, high strength materials, high electric-resistance materials, good wear-resistant materials and brazing materials. Further, since the aluminum-based alloys exhibit superplasticity in the vicinity of their crystallization temperature, they can be successfully processed by extrusion, press working or the like. The processed articles are useful as high strength, high heat resistant materials in many practical applications because of their high hardness and high tensile strength properties. BRIEF DESCRIPTION OF THE DRAWING The single figure is a schematic illustration of a single roller-melting apparatus employed to prepare thin ribbons from the alloys of the present invention by a rapid solidification process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The aluminum-based alloys of the present invention can be obtained by rapidly solidifying melt of the alloy having the composition as specified above by means of liquid quenching techniques. The liquid quenching techniques involve rapidly cooling molten alloy and, particularly, single-roller melt-spinning technique, twin roller melt-spinning technique and in-rotating-water melt-spinning technique are mentioned as especially effective examples of such techniques. In these techniques, the cooling rate of about 10⁴ to 10⁶ °K/sec can be obtained. In order to produce thin ribbon materials by the single-roller melt-spinning technique or twin roller melt-spinning technique, molten alloy is ejected from the opening of a nozzle to a roll of, for example, copper or steel, with a diameter of about 30 - 300 mm, which is rotating at a constant rate of about 300 - 10000 rpm. In these techniques, various thin ribbon materials with a width of about 1 - 300 mm and a thickness of about 5 - 500µ m can be readily obtained. Alternatively, in order to produce wire materials by the in-rotating-water melt-spinning technique, a jet of the molten alloy is directed, under application of the back pressure of argon gas, through a nozzle into a liquid refrigerant layer with a depth of about 1 to 10 cm which is formed by centrifugal force in a drum rotating at a rate of about 50 to 500 rpm. In such a manner, fine wire materials can be readily obtained. In this technique, the angle between the molten alloy ejecting from the nozzle and the liquid refrigerant surface is preferably in the range of about 60° to 90° and the ratio of the relative velocity of the ejecting molten alloy to the relative velocity of the liquid refrigerant surface is preferably in the range of about 0.7 to 0.9. Besides the above techniques, the alloy of the present invention can be also obtained in the form of thin film by a sputtering process. Further, rapidly solidified powder of the alloy composition of the present invention can be obtained by various atomizing processes, for example, high pressure gas atomizing process or spray process. Whether the rapidly solidified aluminum-based alloys thus obtained are amorphous or not can be known by checking the presence of halo patterns characteristic of an amorphous structure using an ordinary X-ray diffraction method. The amorphous structure is converted into a crystalline structure by heating to a certain temperature (called "crystallization temperature") or higher temperatures. In the aluminum alloys of the present invention represented by the above general formula, a, b and c are limited to the ranges of 50 to 93 atomic %, 0.5 to 35 atomic % and 0.5 to 25 atomic %, respectively. The reason for such limitations is that when a, b and c stray from the respective ranges, it is difficult to produce an amorphous structure in the resulting alloys and the intended alloys having at least 50 volume % of amorphous phase can not be obtained by industrial rapid cooling techniques using the above-mentioned liquid quenching, etc. The element M which is at least one metal element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu and Nb has an effect in improving the ability to produce an amorphous structure and greatly improves the corrosion-resistance. Further, the element M not only provides improvements in hardness and strength, but also increases the crystallization temperature, thereby enhancing the heat resistance. Further, since the aluminum-based alloys of the present invention exhibit superplasticity in the vicinity of their crystallization temperatures (crystallization temperature ± 100 °C), they can be readily subjected to extrusion, press working, hot-forging, etc. Therefore, the aluminum-based alloys of the present invention obtained in the form of thin ribbon, wire, sheet or powder can be successfully processed into bulk materials by way of extrusion, pressing, hot forging, etc., at the temperature within the range of their crystallization temperature ± 100 °C. Further, since the aluminum-based alloys of the present invention have a high degree of toughness, some of them can be bent by 180° without fracture. Now, the advantageous features of the aluminum-based alloys of the present invention will be described with reference to the following examples. Examples Molten alloy 3 having a predetermined composition was prepared using a high-frequency melting furnace and was charged into a quartz tube 1 having a small opening 5 with a diameter of 0.5 mm at the tip thereof, as shown in the figure. After heating and melting the alloy 3, the quartz tube 1 was disposed right above a copper roll 2. Then, the molten alloy 3 contained in the quartz tube 1 was ejected from the small opening 5 of the quartz tube 1 under the application of an argon gas pressure of 0.7 kg/cm² and brought into contact with the surface of the roll 2 rapidly rotating at a rate of 5,000 rpm. The molten alloy 3 was rapidly solidified and an alloy thin ribbon 4 was obtained. According to the processing conditions as described above, there were obtained 22 kinds of aluminum-based alloy thin ribbons (width: 1 mm, thickness: 20 µ m) having the compositions (by at.%) as shown in the Table. The thin ribbons thus obtained were subjected to X-ray diffraction analysis and, as a result, halo patterns characteristic of amorphous structure were confirmed in all of the thin ribbons. Crystallization temperature Tx (°K) and hardness Hv (DPN) were measured for each test specimen of the thin ribbons and the results are shown in a right column of the Table. The hardness (Hv) is indicated by values (DPN) measured using a micro Vickers hardness tester under load of 25 g. The crystallization temperature (Tx) is the starting temperature (°K) of the first exothermic peak on the differential scanning calorimetric curve which was obtained at a heating rate of 40°K/min. In the Table, "Amo" represents "amorphous" and "Bri" and "Duc" represent "brittle" and "ductile" respectively. No. Composition Structure Tx (°K) Hv(DPN) Property 1. Al₈₈V₂Ce₁₀ Amo 511 157 Bri 2. Al₈₅Cr₅Ce₁₀ Amo 505 301 Bri 3. Al₈₇Cr₃Ce₁₀ Amo 514 262 Bri 4. Al₈₅Mn₅Ce₁₀ Amo 607 359 Bri 5. Al₈₀Fe₁₀Ce₁₀ Amo 628 1038 Bri 6. Al₈₅Fe₅Ce₁₀ Amo 605 315 Duc 7. Al₈₈Fe₁₀Ce₂ Amo 565 716 Duc 8. Al₈₀Co₁₀Ce₁₀ Amo 626 434 Bri 9. Al₈₈Co₁₀Ce₂ Amo 527 281 Duc 10. Al₈₅Co₅Ce₁₀ Amo 607 305 Duc 11. Al₈₀Ni₁₀Ce₁₀ Amo 625 408 Duc 12. Al₇₀Ni₂₀Ce₁₀ Amo 718 558 Bri 13. Al₆₀Ni₃₀Ce₁₀ Amo 734 652 Bri 14. Al₈₈Ni₁₀Ce₂ Amo 409 330 Duc 15. Al₈₅Ni₅Ce₁₀ Amo 580 265 Duc 16. Al₈₀Cu₁₀Ce₁₀ Amo 499 334 Bri 17. Al₈₅Cu₅Ce₁₀ Amo 512 281 Duc 18. Al₈₀Nb₁₀Ce₁₀ Amo 498 203 Duc 19. Al₈₅Nb₅Ce₁₀ Amo 504 157 Duc 20. Al₈₀Nb₅Ni₅Ce₁₀ Amo 608 338 Bri 21. Al₈₀Fe₅Ni₅Ce₁₀ Amo 667 945 Bri 22. Al₈₀Cr₃Cu₇Ce₁₀ Amo 562 328 Bri As shown in the Table, the aluminum-based alloys of the present invention have an extremely high hardness of the order of about 200 to 1000 DPN, in comparison with the hardness Hv of the order of 50 to 100 DPN of ordinary aluminum-based alloys. It is particularly noted that the aluminum-based alloys of the present invention have very high crystallization temperatures Tx of at least about 440°K and exhibit a high heat resistance. The alloy No. 7 given in the Table was examined for the strength using an Instron-type tensile testing machine. The tensile strength was about 102 kg/mm² and the yield strength was about 95 kg/mm². These values are 2.2 times of the maximum tensile strength (about 45 kg/mm²) and maximum yield strength (about 40 kg/mm²) of conventional age-hardened Al-Si-Fe aluminum-based alloys.

Claims: A high strength, heat resistant aluminum-based alloy having a composition represented by the general formula: Al a M b Ce c wherein: M is at least one metal element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu and Nb; and a, b and c are atomic percentages falling within the following ranges: 50 ≦ a ≦ 93, 0.5 ≦ b ≦ 35 and 0.5 ≦ c ≦ 25, said aluminum-based alloy containing at least 50% by volume of amorphous phase. A high-strength, heat-resistant aluminum-based alloy having a composition represented by the general formula: Al a M b Mm c , wherein: M is at least one metal element selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu and Nb; Mm is a misch metal; and a, b and c are atomic percentages falling within the following ranges: 50 ≦ a ≦ 93, 0.5 ≦ b ≦ 35 and 0.5 ≦ c ≦ 25, said aluminum-based alloy containing at least 50 % by volume of amorphous phase.

Inventors: INOUE, AKIHISA, MASUMOTO, TSUYOSHI, ODERA, KATSUMASA
Applicants: MASUMOTO, TSUYOSHI, YOSHIDA KOGYO K.K.
Application year: 1989
Main classification: C22C21
IPC codes: C22C45, C22C21