High-strength and high-toughness aluminum-based alloy

Abstract: An alloy having a composition represented by the general formula, Al a Ni b X c M d , wherein X is at least one element selected from the group consisting of La, Ce, Mm, Ti and Zr; M is at least one element selected from the group consisting of Fe, Co, Y, Nb, Hf, Ta and W; and a, b, c and d are, in atomic percentages, 85 ≦ a ≦ 94.4, 5 ≦ b ≦ 10, 0.5 ≦ c ≦ 3 and 0.1 ≦ d ≦ 2. The aluminum-based alloy has a high strength and a high toughness and can maintain the excellent characteristics provided by quench solidification even when subjected to thermal influence at the time of working. In addition, the alloy material has a high specific strength due to minimized addition of elements having a high specific gravity.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum-based alloy having a high strength and an excellent toughness which is produced by a quench solidification process. 2. Description of the Prior Art An aluminum-based alloy having a high strength and a high heat resistance has heretofore been produced by a liquid quenching process as disclosed in Japanese Patent Laid-Open No. 275732/1989. The aluminum-based alloy obtained by the liquid quenching process is an amorphous or microcrystalline alloy and is an excellent alloy having a high strength, a high heat resistance and a high corrosion resistance. Further high strength, head resistant aluminum-based alloys are disclosed in EP-A-445684 and EP-A-339676, corresponding to JP-A-1275732. Although the above conventional aluminum-based alloy is an excellent alloy which exhibits a high strength, a high heat resistance and a high corrosion resistance and is also excellent in workability in spite of its being a high-strength material, it still admits of further improvement in toughness when used as a material required to have a high toughness. As a general rule, an alloy produced by a quench solidification process involves the problems that it is susceptible to thermal influence at the time of working and that it suddenly loses its excellent characteristics, such as a high strength, owing to the thermal influence. The above-mentioned aluminum-based alloy is not the exception to the aforestated general rule and still leaves some room for further improvement in this respect. Alloys of the types given in the disclaimer portion of the appended claim are disclosed in EP-A-475101 cited under Art 54(3) EPÜ only. SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a high-strength and high-toughness aluminum-based alloy capable of maintaining its excellent characteristics provided by a quench solidification process, as well as a high strength and a high toughness, even if it is subjected to the thermal influence when working. The present invention provides a high-strength and high-toughness aluminum-based alloy having a composition represented by the general formula Al a Ni b X c M d wherein X is at least one element selected from the group consisting of La, Ce, Mm (misch metal), Ti and Zr; M is at least one element selected from the group consisting of Y, Nb, Hf, Ta and W; and a, b, c and d are, in atomic percentages, 85 ≤ a ≤ 94.4, 5 ≤ b ≤ 10, 0.5 ≤ c ≤ 3 and 0.1 ≤ d ≤ 2, with the exception of the alloys disclosed in EP-A-475101. BRIEF DESCRIPTION OF THE DRAWING The single figure is a schematic illustration of one example of an apparatus well suited for the production of the alloy according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the alloy according to the present invention, the Ni element has a superior ability to form an amorphous phase or a supersaturated solid solution and serves for the refinement of the crystalline structure of the alloy, including the intermetallic compounds, and for the production of a high-strength alloy by a quench solidification process. The content of Ni in the above alloy is limited to 5 to 10 atomic % because a content thereof less than 5 atomic % leads to an insufficient strength of the alloy obtained by rapid quenching, whereas that exceeding 10 atomic % results in a sudden decrease in the toughness (ductility) of the alloy thus obtained. The element X is at least one element selected from the group consisting of La, Ce, Mm, Ti and Zr and serves to enhance the thermal stability of the amorphous structure, supersaturated solid solution or microcrystalline structure as well as the strength of the alloy. The content of the element X in the above alloy is limited to 0.5 to 3 atomic % because a content thereof less than 0.5 atomic % leads to insufficiency of the above-mentioned effect, whereas that exceeding 3 atomic % results in a sudden decrease in the toughness (ductility) of the alloy thus obtained. The element M is at least one element selected from the group consisting of Y, Nb, Hf, Ta and W and serves to enhance the thermal stability of the rapidly solidified structure, such as the amorphous structure, supersaturated solid solution or microcrystalline structure, and to maintain the above-described characteristics, even when the alloy is subjected to thermal influence. The addition of the element M in a slight amount to the alloy does not exert any adverse influence on the excellent toughness (ductility) of the Al-Ni-X-based alloy. The content of the element M in the above alloy is limited to 0.1 to 2 atomic % because a content thereof less than 0.1 atomic % leads to insufficiency of the above-mentioned effect, whereas that exceeding 2 atomic % results in the action of inhibiting the refinement of the aforestated rapidly solidified structure and exerts a bad influence on the toughness (ductility) of the alloy thus obtained. The aluminum-based alloy according to the present invention is obtained by rapidly solidifying the melt of the alloy having the aforestated composition thorough a liquid quenching process. The cooling rate of 10 4 to 10 6 K/sec in this case is particularly effective. Now, the present invention will be described in more detail with reference to the Example. Example A molten alloy 3 having a given composition was prepared with a high-frequency melting furnace, introduced into a quartz tube 1 having a small hole 5 of 0.5 mm in diameter at the end thereof as shown in the figure, and melted by heating. Thereafter, the quartz tube 1 was placed immediately above a copper roll 2. Then the molten alloy 3 in the quartz tube 1 was ejected onto the roll 2 from the small hole 5 of the quartz tube 1 at a high speed of the roll 2 of 3000 to 5000 rpm under a pressure of argon gas of 0.7 kg/cm 2 and brought into contact with the surface of the roll 2 to obtain a rapidly solidified thin ribbon alloy 4. There were obtained by the aforesaid production conditions, 16 kinds of thin ribbons of 1 mm in width and 20 µm in thickness, each having a composition by atomic % as given in Table 1. It was confirmed as the result of X-ray diffraction for each of the ribbons that both amorphous alloys and composite alloys composed of an amorphous phase and a microcrystalline phase were obtained as shown in the right end column in Table 1. The results of observation of the samples of the above composite alloys under a TEM (transmission electron microscope) gave the structure of a mixed phase in which a crystalline phase consisting of FCC (face-centered cubic) was homogeneously and finely dispersed in the amorphous phase. In Table 1, "amorph" and "microcryst" represent "amorphous" and "microcrystalline", respectively. Each of the samples of the above thin ribbons obtained under the aforementioned production conditions was tested for tensile strength, at room temperature and in a 473K (200°C) atmosphere, and toughness (ductility). The results are given on the right-hand column in Table 2. The tensile strength in the 473 K atmosphere was tested at 473 K after the thin ribbon sample was maintained at 473 K for 100 hours. As can be seen from Table 2, the aluminum-based alloy according to the present invention has a very high strength at both room temperature and an elevated temperature, that is, a tensile strength of 850 MPa or higher at room temperature and that of 500 MPa or higher in the 473 K atmosphere without a great decrease in the strength at an elevated temperature; besides, it has an elongation of 1% or greater at room temperature, rendering itself a material excellent in toughness. As has been described hereinbefore, the aluminum-based alloy according to the present invention possesses a high strength and a high toughness and can maintain the excellent characteristics provided by quench solidification, even when subjected to thermal influence at the time of working. In addition, it can provide an alloy material having a high specific strength by virtue of minimized amounts of elements having a high specific gravity to be added to the alloy.

Claims: A high-strength and high-toughness aluminum-based alloy obtained by rapid solidification and having a composition represented by the general formula Al a Ni b X c M d , wherein X is at least one element selected from the group consisting of La, Ce, Mm (misch metal), Ti and Zr; M is at least one element selected from the group consisting of Y, Nb, Hf, Ta and W; and a, b, c and d are, in atomic percentage, 85 ≤ a ≤ 94.4, 5 ≤ b ≤ 10, 0.5 ≤ c ≤ 3 and 0.1 ≤ d ≤ 2, with the exception of aluminum-based alloys having a composition consisting of the general formula Al a M b Ln c , wherein: M is Ni; Ln is at least one element selected from the group consisting of Y, rare earth elements and Mm (misch metal) which is a composite of rare earth elements; and a, b and c are, in atomic percentage, 75 ≤ a ≤ 97, 0.5 ≤ b ≤ 15 and 0.5 ≤ c ≤ 10, the alloy being composed of an aluminum matrix or an aluminum supersaturated solid solution matrix having an average crystal grain size of 0.1 to 80 µm and containing therein a uniform dispersion of metastable or stable phase particles composed of intermetallic compounds, which are formed between the host element (matrix element) and the above-mentioned alloying elements and/or between the alloying elements, the intermetallic compounds having an average particle size of 10 to 500 nm; and the aluminum-based alloys having a composition consisting of the general formula Al a M b X d Ln c , wherein: M is Ni; X is at least one metal element selected from the group consisting of Ti and Zr; Ln is at least one element selected from the group consisting of Y, rare earth elements and Mm (misch metal) which is a composite of rare earth elements; and a, b, c and d are, in atomic percentage, 75 ≤ a ≤ 97, 0.5 ≤ b ≤ 15, 0.5 ≤ c ≤ 10 and 0.5 ≤ d ≤ 3.5, the alloy being composed of an aluminum matrix or an aluminum supersaturated solid solution matrix having an average crystal grain size of 0.1 to 80 µm and containing therein a uniform dispersion of metastable or stable phase particles composed of intermetallic compounds, which are formed between the host elements (matrix element) and the above-mentioned alloying elements and/or between the alloying elements, the intermetallic compounds having an average particle size of 10 to 500 nm.

Inventors: KAWANISHI MAKOTO, KITA KAZUHIKO, NAGAHAMA HIDENOBU, TERABAYASHI TAKESHI, KAWANISHI, MAKOTO, KITA, KAZUHIKO, NAGAHAMA, HIDENOBU, TERABAYASHI, TAKESHI
Applicants: YKK CORP, YKK CORPORATION
Application year: 1992
Main classification: C22C45
IPC codes: C22C21, C22C45