Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0408—Light metal alloys
  • C22C1/0416—Aluminium-based alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent

Definitions

• the present invention relates to an aluminum alloy which provides a product having a highly improved strength at elevated temperatures and remarkable resistance to creep when used in powder metallurgy process.
• P/M process Products of aluminum alloy prepared by powder metallurgy process (hereinafter referred to as "P/M process”) exhibit highly improved heat resistance, wear resistance, and like properties in comparison with the products prepared by ingot metallurgy process (hereinafter referred to as "IM process”) because the products by P/M process can contain additional elements in larger amounts with no segregation and much more uniformly dispersed in aluminum matrix than the products prepared by IM process.
• IM process ingot metallurgy process
• P/M aluminum alloy products are usually produced by hot extrusion of a powdery, flaky or ribbon-like quickly solidified material to obtain a billet and processing the billet to the desired shapes or forms.
• the oxide films on the surfaces of powder particles, flakes or ribbons are fractured and the exposed inner aluminum portions are pressed each other to form strong bonding.
• powder-­rolling process and powder-forging process which also belong to a general category of P/M process, aluminum oxide films are fractured; however, since shearing force is relatively small and deformation of each particle is not so large and uniform as in the case of extrusion, the bond between particles is not so strong as in the extruded product.
• the extrusion ratio in conducting the above extrusion by P/M process is usually 10 or more, preferably 20 or more to obtain a strong bonding of each particle.
• the extrusion by P/M process usually requires much higher forces than the extrusion by IM process because the aluminum alloy used in the former process contain larger amounts of alloying elements. For these limitations, aluminum alloy materials obtained by P/M process are difficult to employ for producing large-sized products.
• An object of the invention is to provide a P/M aluminum alloy which can be extruded under a low extrusion ratio of 10 or lower.
• Another object of the invention is to provide a P/M aluminum alloy which can be extruded even under an extremely low extrusion ratio of 2 to 5.
• Still another object of the invention is to provide a P/M aluminum alloy capable of producing an extruded product excellent in strengths at high temperatures and resistance to creep.
• the present invention provides a P/M aluminum alloy consisting essentially of (a) 5 to 30% by weight of Si, (b) 0.5 to 10% by weight of at least one species selected from the group consisting of Fe, Ni, Cr and Mn with the proviso that the total amount of these species cannot exceed 20% by weight, (c) 0.3 to 3% by weight of at least one species selected from the group consisting of Mo, Zr, V and Ti with the proviso that the total amount of these species cannot exeed 5% by weight, and (d) aluminum in a remaining amount.
• the aluminum alloys used in the invention contain as alloying elements (a) 5 to 30% by weight or Si, (b) 0.5 to 10% by weight of at least one species selected from the group consisting of Fe, Ni, Cr and Mn with the proviso that the total amount of these species cannot exceed 20% by weight and (c) 0.3 to 3% by weight of at least one species selected from the group consisting of Mo, Zr, V and Ti with the proviso that the total amount of these species cannot exceed 5% by weight.
• the aluminum alloys of the invention with the above specific components are extruded, the powder particles are strongly bonded each other even at a low extrusion ratio and the extruded material exhibits substantially uniform strength and elongation irrespective of the extrusion ratio. If an aluminum alloy powder with the composition outside the above specified range is used, an extruded material with strong bonding cannot be obtained at a low extrusion ratio of 10 or 5 to 2 at a temperature of 400 to 500°C.
• the amount of Si is less than 5% by weight of the alloy, the bonding strength of the particles is low; whereas the use of Si of more than 30% by weight results in the excess volume of primary Si particles in the matrix which leads to a reduction in the toughness of the alloy.
• Fe, Ni, Cr and Mn mainly contribute to the improvement of heat resistance and strength.
• the amount of at least one of Fe, Ni, Cr and Mn in less than 0.5% by weight results in inferior heat resistance and strength of the extruded material whereas the amount thereof in more than 10% by weight results in lower toughness with the formation of coarse intermetallic compounds.
• the total amount of these alloying elements in excess of 20% by weight also leads to a reduction of toughness of the alloy.
• Mo, Zr, V and Ti mainly contribute to the improvement of heat resistance and creep resistance.
• the amount of at least one of Mo, Zr, V and Ti in less than 0.3% by weight does not significantly improve the resistance to heat and creep.
• the amount thereof exceeds 3% by weight coarse intermetallic compounds are formed to lower the toughness of the alloy.
• the total amount is up to 5% by weight of the alloy to prevent the formation of coarse intermetallic compounds which lead to reduced toughness.
• the aluminum alloy of the invention contains 5 to 30% by weight of Si, 2 to 5% by weight of Fe, 2 to 5% by weight of Hi and 1 to 3% by weight of Mo.
• the aluminum alloy of the invention containing alloying elements in the preferable ranges exhibits balanced properties of the high strengths at elevated temperatures, resistance to creep and toughness.
• the aluminum alloy of the invention contains 5 to 30% by weight of Si, 2 to 5% by of Fe, 2 to 5% by weight of Ni, 0.5 to 3% by weight of Mo and 0.5 to 3% by weight of Zr provided that the total amount of Mo and Zr is more than 2% by weight and less than 5% by weight.
• the aluminum alloy of the invention containing alloying elements in the more preferable ranges shows much more balanced properties of the improved strengths, toughness and resistance to creep at elevated temperatures.
• the aluminum alloys with alloying elements in a more preferable range are most useful as the materials for machine components, etc.
• the extruded product formed from the aluminum alloy of the invention exhibits high resistance to heat and creep.
• Table 1 Aluminum alloys containing alloying elements as indicated Table 1 below were air-atomized into particles and sieved to prepare powders of minus 100 mesh.
• Each of the aluminum alloy powders thus prepared was cold pressed to a preform 30 mm in diameter and 80 mm in height and then extruded at 450°C at an extrusion ratio of 3. Test pieces were prepared from the extruded materials, and tensile tests and creep tests were conducted at 300°C.
• rupture time indicates a period of time required for a test piece to rupture when it is exposed to a stress of 8 kg/mm2 at 300°C.
• Table 2 indicates that the extruded materials obtained from the aluminum alloys of the invention (Nos.1 to 16) have high tensile strength and elongation and exhibit good resistance to creep. Particularly, the extruded products produced from alloy Nos.13 to 16 are balanced in resistance to creep, tensile strength at elevated temperatures and toughness.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Powder Metallurgy (AREA)

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• 1989
  • 1989-10-26 EP EP89119912A patent/EP0366134B1/de not_active Expired - Lifetime

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