Classifications

• • 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
• • 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
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent

Definitions

• This invention is concerned with aluminium alloys containing copper, manganese and titanium and articles made from such alloys.
• Wrought or hot worked alloys of aluminium containing copper, manganese and titanium have been used for aero-engine components operating at elevated temperatures and have found particular application for service in the temperature range 200-300 C. Although alloys of this type have satisfactory properties at temperatures in this range, an improvement in the room temperature and lower elevated temperature tensile properties, particularly the proof stress values and the creep resistance, is desirable.
• the alloys may contain the normal amounts of impurities, which may, for example, consist of or include one or more of the elements nickel, chromium and Zinc, in
• the invention provides an aluminium al loy containing the following elements in the following proportions by weight:
• the alloys are particularly suitable for aero-engine components and for aircraft skinning and structural members which are required to withstand complex stress systems at elevated temperatures for long service lives.
• the alloys should after working be solution heat-treated for up to 30 hours between 515 and 550 C., quenched and then artificially aged for 5 to 36 hours between 170 and 250 C.
• the solution heat-treated article may be quenched in oil or water or molten salt.
• the maximum properties will be developed in parts which have been quenched by the most rapid means but such rapid quenching may result in too high a level of residual internal stress in certain designs of component. Therefore, for these critical applications, quenching into hot or boiling water or molten salt at 250 C. may be employed. These latter two quenching treatments very significantly reduce the internal stress level, with concomitant reductions in room temperature and elevated temperature properties but the levels of strength are still significantly higher than those of comparable parts in the alloys Without magnesium.
• alloys made according to this invention when solution heat-treated and then quenched into molten salt and subsequently artificially aged, were the only aluminium base alloys of those tested which showed a satisfactory low degree of distortion during the machining.
• the artificial ageing time and temperature will depend on the required service life and operational temperature envisaged for the alloy article. For service at room or moderately elevated temperatures, ageing treatments at temperatures between about and 200 C. are employed but for service above about C., higher temperatures in the range to 250 C. produce the optimum elevated temperature performance. Ageing at temperatures above 210 C. is required to expand fully the crystal lattice so that no further significant dimensional changes will occur during prolonged service at elevated temperatures.
• the optimum solution treatment temperature is 525 to 535 C. and the optimum time of treatment will depend on the particular wrought form and section thickness but will be, for forgings and extrusions, in the range /2 to 20 hours, and, for sheet and strip, for up to 8 hours (nomally between 5 minutes and 2 hours).
• the best balance of room and elevated temperature mechanical properties is obtained after artificial ageing for 8 to 24 hours at 190 to 200 C. in the case of sheet and extrusions, and for the same time but at 210 to 220 C. for forgings.
• a reduced solution treatment temperature of the order of 515 to 525 C. is necessary in each case in order to avoid the phenomenon of overheating, due to the liquation of low melting point constituents consisting of complex eutectics containing aluminium, copper, and magnesium.
• the presence of overheating is undesirable because it causes blistering and can result in a reduction in one or more of the mechanical properties, in particular, fatigue and creep resisting properties.
• Overheating in the microstructure of wrought products is not acceptable for highly stressed components, for example, in aircraft skinning and structural members and aero-engine parts. Although the phenomenon of over-heating may as mentioned above be avoided by the use of lower solution heat-treatment temperatures than in the preferred range, this results in a reduction in mechanical properties.
• the alloys made according to the invention show particularly advantageous properties in the form of rolled sheet or strip.
• the alloys may be used unclad or clad on one or both major faces with a layer of commercially pure aluminium, or with an alloy compounded of commercially pure aluminium and 0.8 to 1.2 percent by weight of zinc, or with a corrosionresistant, heat-treatable aluminium base alloy containing 0.4 to 1.4 percent magnesium, 0.2 to 1.3 percent silicon, 0.0 to 1.0 percent manganese, 0.0 to 0.3 percent chromium, and 0.8 to 1.2 percent zinc, all percentages being by weight, the balance being aluminium and the normal amounts of impurities and grain refining elements found in such alloys.
• Alloys A to I were cast by the semi-continuous casting process, alloys A to E and F to I being cast in round billets and rectangular rolling slabs, respectively.
• the billets in alloys A to B were forged in the normal way into 1 inch diameter bar.
• the bars were solution heat-treated for 20 hours at 530 C., unless specified to the contrary in the various tables, quenched into boiling water and then artificially aged for 16 hours at 215 C.
• Suitable test-pieces were cut and machined from forged bars in each of the alloys and were tensile tested at room and elevated temperature, creep tested and fatigue endurance tested according to the various schedules in Tables 2, 3 and 4. The results of these tests are also given in the same tables.
• tons/s tons/sq. Elong. P.S. tons/sq. Elong. P.S., tons/sq. Elong. in. percent tons/sq. in. percent tons/sq, in. percent in. in.
• Cladding plates in an alloy compounded of commercially pure aluminum and about 1% zinc were strapped by means of steel bands to each of the major sides of cast rolling slabs in each of the Alloys F to J, the thickness of each cladding plate being about 5% of the total thickness of the composite.
• the clad slabs were preheated and hot rolled in the normal manner to about 0.25-inch thickness and then cold rolled into sheet, 0.064-inch thick, with several inter-stage annealing treatments, in accordance with the practices normally used in the art.
• Sample sheets in alloys F, G and H were solution heat-treated in a salt bath for 30 minutes at 530 C., quenched in cold water and stretched to straighten in the usual manner.
• sheets in alloys I and I were solution heat-treated at 525 and 520 C., respectively.
• the sheets in the silver-free alloys, Alloys F, G and H, were artificially aged for 16 hours at 195 C.
• the silvercontaining sheets, Alloys I and I were aged for 16 hours at 180 C.
• Additional sheets in Alloy H were solutiontreated at 530 C., quenched and aged for 16 hours at 180 C. for comparison purposes.
• Suitable test blanks were taken in the transverse direction from random locations in the sheet in each alloy and machined into appropriate test-pieces. The specimens were then tensile tested at room and elevated temperature and The improvement in room and elevated temperature tensile properties and in creep resistance, resulting from the addition of 0.20 and 0.31% magnesium to sheet, made according to this invention, and the superiority of sheet with a magnesium content within the preferred range specified hereinbefore, namely 0.25 to 0.4% magnesium, is obvious on comparing the results presented in Table 5 for clad sheet in Alloys F, G and H.
• Alloys K, L and M were semi-continuously cast into round billets and hot extruded in the normal manner into 1 in. diameter bar. Sample lengths of bar in each alloy were solution treated for 5 hours at 530 C., quenched in cold water and artificially aged for 16 hours at 195 C. and another length in Alloy L was artificially aged for 16 hours at C. after solution treatment and quenching. A further length in Alloy M was solution treated for 5 hours at 520 C., followed by quenching in cold water and ageing for 16 hours at C. Suitable longitudinal test-pieces were machined from the bars in the various conditions of heat-treatment and tensile and creep tested at room temperature and 175 C., respectively, according to the schedules in Table 7, which also contain the test results.
• a method of making a wrought article from an aluminum alloy according to claim 1, comprising working said alloy into a predetermined form of article, solution heat-treating said article for up to hours between 515 and 550 C., quenching the heat-treated article and then artificially aging the thus-treated article for 5 to 36 hours between and 250 C.
• a method of making a wrought article from an aluminum alloy according to claim 2 comprising forging said alloy, solution heat-treating the resulting article for /2 to 20 hours between 525 and 535 C., quenching the heat-treated forged article and then artificially aging the quenched article.
• a method of making a wrought article from an aluminum alloy according to claim 2 comprising extruding said alloy, solution heat-treating the resulting article for /2 to 20 hours between 525 and 535 C., quenching the heat-treated extruded article and then artificially aging the quenched article.
• a method of making a wrought article from an aluminum alloy according to claim 2, comprising rolling said alloy, solution heat-treating the resulting article for up to 8 hours between 525 and 535 C., quenching the heattreated article and then artificially aging the quenched article.
• a method of making a wrought article from an aluminum alloy according to claim 3, comprising forging said alloy into a predetermined form of article, solution heat-treating said article for /2 to 20 hours between 515 and 535 C., quenching the heat-treated article and then artificially aging the thus-treated article.
• a method of making a wrought article from an alloy according to claim 3, comprising extruding said alloy, solution heat-treating the resulting article for up to 8 hours between 525 and 535 C., quenching the heattreated article, and then artificially aging the quenched article.
• a method of making a wrought article from an aluminum alloy according to claim 3, comprising rolling said alloy, solution heat-treating the resulting article for up to 8 hours between 520 and 530 C., quenching said heattreated article and then artificially aging the quenched article.
• a method of making a wrought article according to claim 9 wherein said artificial ageing is for 8 to 24 hours between 190 and 200 C.
• a method of making a wrought article according to claim 21 wherein said artificial ageing is for 8 to 24 hours between and C.

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

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Cited By (11)

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Citations (4)

• 0
  • BE BE668895D patent/BE668895A/xx unknown
• 1964
  • 1964-08-28 GB GB35443/64A patent/GB1089454A/en not_active Expired
• 1965
  • 1965-08-25 US US482598A patent/US3414406A/en not_active Expired - Lifetime
  • 1965-08-25 DE DE19651483228 patent/DE1483228B2/de active Pending
  • 1965-08-27 SE SE11231/65A patent/SE334748B/xx unknown
  • 1965-08-27 NL NL6511260A patent/NL6511260A/xx unknown
  • 1965-08-28 CH CH1209865A patent/CH476107A/de not_active IP Right Cessation

Patent Citations (4)

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