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

Definitions

• the invention relates to a highly heat-resistant aluminum alloy consisting essentially of an aluminum matrix which contains a dispersion mixture of solidifying Al-Fe particles, part of the Fe content being at least one of the most refractory elements titanium, zirconium, niobium, molybdenum, tungsten, chromium and vanadium including nickel and cobalt can be replaced.
• the invention was therefore based on the object of developing new wrought aluminum alloys which can be produced from powder particles of a relatively large average particle size and can be easily processed, and which not only have good heat resistance with high RT strength at the same time but also show improved corrosion behavior and higher fatigue strength.
• this object is achieved by the alloys and methods for producing objects from certain alloy elements specified in the patent claims. It was not to be expected that copper and manganese additions in a content of more than 1% lead to good strength behavior over temperature, since the person skilled in the art knew from various references that precipitation hardening occurs with AlCuMn alloys. This would be disadvantageous in the case of reheating, since the Al2Cu (Mn) phases become coarser by dissolving the sub-excretions (Ostwald ripening) and the strength-increasing effect is lost.
• the test evaluation shows that the heat resistance of the developed alloys is determined by the formation of fine, stable intermetallic phases of the AlCuMn, Al3Fe, Al3Ni and Al9Co2 type and their mixed phases. At the same time, a high room temperature strength with RT strengths of up to 6OO N / mm2 could be achieved.
• Very stable intermetallic phases which separate out due to the rapid solidification process of the melt (average particle size less than 1 ⁇ m), are formed from the alloying elements iron, nickel and cobalt. These fine, stable, intermetallic phases of aluminum are distributed in the aluminum alloy at levels between 2O-4O% and have a positive influence on the corrosion behavior.
• the wrought aluminum alloys according to the invention are produced in comparison to continuous casting at average quenching speeds of 1O2-1O4 K / s.
• the average quenching speed of the alloy from the melt is achieved by gas atomization, melt spinning, production of particles using the centrifugal mold process, among others. These rapidly solidified particles can then by known Powder metallurgical processes for semi-finished products, such as extruded products, parts produced by explosion compression, etc. are processed.
• the atomization of the alloy according to the invention leads to fine dendrite gaps (cell sizes), while an AlCuMn alloy produced by continuous casting has a cell size of approximately 50 ⁇ m, the average cell size according to the present invention is approximately 0.5 ⁇ m.
• the solubility of the alloy elements according to the invention in aluminum and thus the alloy content of the usual wrought aluminum alloys is significantly increased.
• the addition of O, 4-2, O% titanium, zirconium and chromium to the aluminum alloy enables the formation of very fine phases ⁇ O, 2 ⁇ m in a proportion of 80%.
• the heat resistance is significantly increased due to the low diffusion coefficient and the fine, stable intermetallic phases of aluminum with these elements.
• the spherical particles only form when the ratio of copper: manganese is in the range from 2: 1 to 1: 1.
• the strength or the machinability decrease.
• the powdery particles have an average particle size larger than 8O ⁇ m, preferably 1OO-2OO ⁇ m, if the compression before the forming leads to a minimum density of the block of 7O-85%.
• high extrusion speeds of 5-1O m / sec can be achieved.
• powder particles of 16O microns in the alloy according to the invention still have a very fine casting structure (cell size).
• very fine, rounded particles are formed from the casting structure by heterogeneous nucleation and shaping by the forming process. These fine, rounded particles allow a high extrusion speed of the alloys according to the invention.
• the high press speeds mean that economical production is endangered, although the forming forces for the P / M alloys naturally increase due to the high alloy contents.
• the special alloy contents according to the invention also ensure higher extrusion temperatures up to 5OO ° C. without greater impairment of the mechanical properties than is described for comparable metastably supersaturated P / M alloys in US Pat. No. 4,464,199.
• the very fine, homogeneous structure of rounded particles in the alloy according to the invention ensures that there are no pik-ups (chatter marks due to local melting).
• the extruded profiles show particularly good smooth surfaces, which are almost without any defects and perfectly anodizable.
• the fatigue strength of the heat-resistant alloys according to the invention is better than 250 N / mm 2 and thus not only better than conventional aluminum alloys with particularly good fatigue strengths, but also better than comparable heat-resistant aluminum P / M alloys. This high fatigue strength applies both at RT and at 150 ° C.
• the particularly high elastic modulus is also particularly characteristic of the heat-resistant Al-P / M alloys according to the invention.
• the modulus of elasticity is 85-1OO G Pa compared to 72 G Pa for the conventional heat-resistant Al alloy AA 2618.
• a conventional heat-resistant wrought aluminum alloy which was produced by continuous casting, contains 2.7% copper, O, 2% manganese and 1.2% magnesium.
• the mechanical properties that can be achieved after precipitation hardening are summarized in Table 1.
• the good corrosion behavior of the alloy according to the invention was assessed on the basis of the following test experiments:
• the alloys according to the invention not only show good behavior with respect to general corrosion but are also particularly well resistant to corrosion under stress or stress corrosion cracking. Stress corrosion cracking was tested in the critical transverse direction (LT) in 2% NaCl + O, 5% Na2CrO4 / pH 3 under constant stress.
• LT critical transverse direction
• the AA 2618 I / M is not SRK-resistant, while the Al2Cu1.5Mn4Fe4Ni-P / M alloy is SRK-resistant.
• the alloy according to the invention contains 0.5-1.5% magnesium.
• the addition of magnesium does not lead to an improvement due to precipitation hardening, because aging treatment between 12 ° C and 22 ° C does not lead to an increase in the F-values or there is no dependence of the F-values on the aging conditions.
• the magnesium additive leads through the formation of fine magnesium oxide in the P / M semifinished product - which can increase strength like intermetallic phases - through a reduction in the defects of the quenched alloys - as defects - "sink" etc. - to an improvement in the mechanical Properties of the Al-P / M alloy.

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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)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Casings For Electric Apparatus (AREA)
• Coating With Molten Metal (AREA)
• Compositions Of Oxide Ceramics (AREA)

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• 1985
  • 1985-09-18 DE DE19853533233 patent/DE3533233A1/de not_active Withdrawn
• 1986
  • 1986-08-02 EP EP86110727A patent/EP0219629B1/fr not_active Expired
  • 1986-08-02 AT AT86110727T patent/ATE47890T1/de not_active IP Right Cessation
  • 1986-08-27 NO NO863441A patent/NO168257C/no unknown
  • 1986-09-16 ES ES8601919A patent/ES2000977A6/es not_active Expired
  • 1986-09-18 US US06/908,554 patent/US4832737A/en not_active Expired - Fee Related
  • 1986-09-18 JP JP61218270A patent/JPS6274042A/ja active Pending

Patent Citations (5)

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