US3598663A - Aluminum alloy heat-treating - Google Patents

Aluminum alloy heat-treating Download PDF

Info

Publication number
US3598663A
US3598663A US715527A US3598663DA US3598663A US 3598663 A US3598663 A US 3598663A US 715527 A US715527 A US 715527A US 3598663D A US3598663D A US 3598663DA US 3598663 A US3598663 A US 3598663A
Authority
US
United States
Prior art keywords
alloy
heat
temperature
treating
hours
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US715527A
Inventor
Herbert Greenewald Jr
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Boeing North American Inc
Original Assignee
North American Rockwell Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by North American Rockwell Corp filed Critical North American Rockwell Corp
Application granted granted Critical
Publication of US3598663A publication Critical patent/US3598663A/en
Assigned to GREENWALD, JOAN K. (SURVIVING SPOUSE) reassignment GREENWALD, JOAN K. (SURVIVING SPOUSE) ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: GREENWALD, JOAN K., EXECUTOR OF HERBERT GREENWALD, JR.
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/053—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with zinc as the next major constituent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
    • B22D21/002—Castings of light metals
    • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
    • 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
    • C22C1/02—Making non-ferrous alloys by melting

Definitions

  • Aluminum alloys having a significant zinc, magnesium, or other strong hydride former content, and particularly if melted, poured, or solidified in an environment containing excessive hydrogen, hydrocarbon, or water vapor constituents, are solution and homogenization heat-treated in accordance with this invention in a vacuum environment at a temperature in the range extending from the alloy solidus temperature to the alloy solid solubility limit temperature a sufficient time.
  • heattreatment in a vacuum of 2 10 mm. Hg at a temperature of 860 F.:40 F. for 24 hours per 0.1 of solidified alloy thickness aids substantially in obtaining improved physical and metallurigical properties.
  • the solutioned and homogenized alloy is preferably immediately quenched and subjected to post-heat-treat aging such as on an accelerated basis by heating at from 250 F. to 450 F. for from 24 hours to 2 hours.
  • compositions are stated on a percentage part by weight basis and are characterized as having a significant 3,598,663 Patented Aug. 10, 1971 zinc, magnesium, or other strong hydride former content.
  • the instant invention does not involve melting, pouring, or completely solidifying alloy compositions and such may be accomplished conventionally or even in accordance with the pre-heat treatment method disclosed and claimed in the above-cross-reference application for United States patent, for instance, depending on application requirements.
  • significant advantages may be attained if the completely solidfied alloy is solution and homogenization heat-treated according to the following method, particuarly if allo melting, pouring, or solidification prior to heat-treatment has been accomplished in an environment having excess hydrogen, hydrocarbons, or water vapor.
  • the first step in the preferred solution and homogenization heat-treating method involves placing the solidified aluminum alloy having a significant zinc, magnesium, or other strong hydride former content in a furnace chamber that may be sealed and pumped down to a continuous vacuum condition. Solution and homogenization is then accomplished after the chamber pressure is reduced to a vacuum such as 2x10" mm. Hg. (absolute).
  • the preferred temperature for such heat-treating will vary in relation to the alloy composition. In the case of the modified 7075-type material, 860 F.i40 is generally preferred. Alloy 220 can be heat-treated at a temperature in the range of 800 F. -4O F.; 950 F. i40 F. is considered satisfactory for heat-treating the other alloy detailed as to composition in Table 1.
  • Such heat-treating temperatures, in each instance, are in the temperature range from the alloy solidus temperature to the alloy solid solubility limit temperature. For the alloys specified in Table I, 24 hours at temperature per 0.1" of metal thickness is generally satisfactory from the standpoint of time.
  • Post-heat-treat cooling follows the vacuum solution and homogenization heat-treating step and preferably occurs at cooling rates that are sufiiciently high to obtain a non-equilibrium metallurgical structure. It is therefore preferred that the alloys of Table I be immediately quenched from the solution and homogenization heattreating temperature to ambient temperature in ambient temperature water, equipment permitting. This differs from the normal practice of accomplishing post-heat-treat cooling in heated water such as 180 F., for instance and with an intermediate heating following cooling in air.
  • the quenched alloy may be aged naturally or by conventional accelerated aging steps.
  • accelerated aging temperature-time histories in the range of from 450 F. for 2 hours to 250 F. for 24 hours are adequate. No environmental controlled atmosphere or environmental controlled pressure is required. 1
  • a casting alloy having a composition of the type corresponding to the modified 7075-type aluminum alloy set forth in Table I was melted, poured, and directionally solidified in accordance with the pre-heat-treatment method set forth in the description and drawings of the cross-reference application for United States patent.
  • the mold cavity incorporated the external configuration of a missile fin and included a joining riser region positioned above the fin configuration region.
  • a portion .of the completed casting was solution and homogenization heattreated in a 2X 10- mm. Hg continuously pumped vacuum environment at a temperature of approximately 860 F. for 48 hours. Since the available heat-treating equipment did not permit quenching directly from temperature, the part was air-cooled after solution and homogenization heat-treating and afterwards heated to 860 F. in an air furnace for 2 hours and then water-quenched as specified. Round tensile test bars were machined from coupons cut from the casting and were found to have the properties set forth in the following Table II.
  • the solidified 7075-type alloy was solution and homogenization heat-treated conventionally in an argon atmosphere just above standard atmospheric pressure at a temperature of 860 F. for 72 hours.
  • the casting portion was air-cooled, reheated to 860 F. for 2 hours in air, water-quenched, and aged as specified (i.e., 24 hours at 250 F.).
  • a coupon from the casting portion so heat-treated, cooled, and aged was found to have a yield tensile strength of 55,300 p.s.i., an ultimate tensile strength of 56,100 p.s.i., and percent elongation of 1.2%.
  • Vacuum pressure levels are selected with reference to the apparent volatility of alloy constituents at the metal temperature involved and so as to preclude alloying constituent depletion due to processing requirements. More specifically, a vacuum environment of 1 10- mm. Hg has been determined to be unsatisfactory in at least one instance wherein the aluminum alloy zinc content was undesirably reduced from 5.5% to 0.2%.
  • a casting having an aircraft elevator fitting configuration was cast in an alloy whose melt composition (average) consisted of 1.47% copper, 5.62% zinc,-2.6l% magnesium, 0.2% titanium, 0.16% beryllium, O.l% manganese, O.l% chromium, 0.1% iron, 0.08% silicon, and the balance aluminum, using the pre-heat-treatment melting, pouring, and directional solidification steps disclosed in the cross-reference application for United States patent. After conventional heat-treating in an argon atmosphere at 860 F. for 72 hours followed by quenching and conventional accelerated aging. Coupons cut from the so-processed casting were found to have ultimate tensile strengths from 58,900 p.s.i.
  • a method of heat treating a precipitation hardenable aluminum alloy to develop improved physical and metallurgical properties comprising the steps of:

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)

Abstract

A METHOD FOR HEAT-TREATING ALUMINUM ALLOYS WHEREIN THE COMPLETELY SOLIDIFIED MATERIAL IS SOLUTION AND HOMOGENIZATION HEAT-TREATED IN A VACUUM ENVIRONMENT AT A TEMPERATURE IN THE RANGE EXTENDING FROM THE ALLOY SOLIDUS TEMPERATURE TO THE ALLOY SOLID SOLUBILITY LIMIT TEMPERATURE A SUFFICIENT TIME TO DEVELOP IMPROVED PHYSICAL AND METALLURGICAL PROPERTIES UPON SUBSEQUENT COOLING AND AGING.

Description

United States Patent 3,598,663 ALUMINUM ALLOY HEAT-TREATING Herbert Greenewald, Jr., Columbus, Ohio, assignor to North American Rockwell Corporation No Drawing. Original application Mar. 13, 1968, Ser. No. 712,674, now Patent No. 3,515,546, dated June 2, 1970. Divided and this application Mar. 25, 1968, Ser. No.
Int. Cl. C21d 1/74 US. Cl. 148-159 4 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCE This application is a division of application for US. Pat. Ser. No. 712,674, filed Mar. 13, 1968 for Aluminum Alloy solidification, issued June 2, 1970 as US. Pat. No. 3,515,546, and assigned to the assignee of this application.
SUMMARY OF THE INVENTION Aluminum alloys having a significant zinc, magnesium, or other strong hydride former content, and particularly if melted, poured, or solidified in an environment containing excessive hydrogen, hydrocarbon, or water vapor constituents, are solution and homogenization heat-treated in accordance with this invention in a vacuum environment at a temperature in the range extending from the alloy solidus temperature to the alloy solid solubility limit temperature a sufficient time. For 7075-type aluminum alloys modified for casting applications, for instance, heattreatment in a vacuum of 2 10 mm. Hg at a temperature of 860 F.:40 F. for 24 hours per 0.1 of solidified alloy thickness aids substantially in obtaining improved physical and metallurigical properties. Afterwards, the solutioned and homogenized alloy is preferably immediately quenched and subjected to post-heat-treat aging such as on an accelerated basis by heating at from 250 F. to 450 F. for from 24 hours to 2 hours.
DETAILED DESCRIPTION The heat-treating method of this invention has application to the type of aluminum alloy detailed as to composition in the following Table I:
Such compositions are stated on a percentage part by weight basis and are characterized as having a significant 3,598,663 Patented Aug. 10, 1971 zinc, magnesium, or other strong hydride former content.
The instant invention does not involve melting, pouring, or completely solidifying alloy compositions and such may be accomplished conventionally or even in accordance with the pre-heat treatment method disclosed and claimed in the above-cross-reference application for United States patent, for instance, depending on application requirements. However, significant advantages may be attained if the completely solidfied alloy is solution and homogenization heat-treated according to the following method, particuarly if allo melting, pouring, or solidification prior to heat-treatment has been accomplished in an environment having excess hydrogen, hydrocarbons, or water vapor.
The first step in the preferred solution and homogenization heat-treating method involves placing the solidified aluminum alloy having a significant zinc, magnesium, or other strong hydride former content in a furnace chamber that may be sealed and pumped down to a continuous vacuum condition. Solution and homogenization is then accomplished after the chamber pressure is reduced to a vacuum such as 2x10" mm. Hg. (absolute). The preferred temperature for such heat-treating will vary in relation to the alloy composition. In the case of the modified 7075-type material, 860 F.i40 is generally preferred. Alloy 220 can be heat-treated at a temperature in the range of 800 F. -4O F.; 950 F. i40 F. is considered satisfactory for heat-treating the other alloy detailed as to composition in Table 1. Such heat-treating temperatures, in each instance, are in the temperature range from the alloy solidus temperature to the alloy solid solubility limit temperature. For the alloys specified in Table I, 24 hours at temperature per 0.1" of metal thickness is generally satisfactory from the standpoint of time.
Post-heat-treat cooling follows the vacuum solution and homogenization heat-treating step and preferably occurs at cooling rates that are sufiiciently high to obtain a non-equilibrium metallurgical structure. It is therefore preferred that the alloys of Table I be immediately quenched from the solution and homogenization heattreating temperature to ambient temperature in ambient temperature water, equipment permitting. This differs from the normal practice of accomplishing post-heat-treat cooling in heated water such as 180 F., for instance and with an intermediate heating following cooling in air.
Afterwards, the quenched alloy may be aged naturally or by conventional accelerated aging steps. In terms of the aluminum alloys of Table I, accelerated aging temperature-time histories in the range of from 450 F. for 2 hours to 250 F. for 24 hours are adequate. No environmental controlled atmosphere or environmental controlled pressure is required. 1
A casting alloy having a composition of the type corresponding to the modified 7075-type aluminum alloy set forth in Table I was melted, poured, and directionally solidified in accordance with the pre-heat-treatment method set forth in the description and drawings of the cross-reference application for United States patent. The mold cavity incorporated the external configuration of a missile fin and included a joining riser region positioned above the fin configuration region. A portion .of the completed casting was solution and homogenization heattreated in a 2X 10- mm. Hg continuously pumped vacuum environment at a temperature of approximately 860 F. for 48 hours. Since the available heat-treating equipment did not permit quenching directly from temperature, the part was air-cooled after solution and homogenization heat-treating and afterwards heated to 860 F. in an air furnace for 2 hours and then water-quenched as specified. Round tensile test bars were machined from coupons cut from the casting and were found to have the properties set forth in the following Table II.
Another portion of the same casting was subjected to a different heat-treatment and then subjected to testing. specifically, the solidified 7075-type alloy was solution and homogenization heat-treated conventionally in an argon atmosphere just above standard atmospheric pressure at a temperature of 860 F. for 72 hours. The casting portion was air-cooled, reheated to 860 F. for 2 hours in air, water-quenched, and aged as specified (i.e., 24 hours at 250 F.). A coupon from the casting portion so heat-treated, cooled, and aged was found to have a yield tensile strength of 55,300 p.s.i., an ultimate tensile strength of 56,100 p.s.i., and percent elongation of 1.2%.
The completed and heat-treated casting portions were examined radiographically and found to be free of observable defects, particularly as to pin-hole porosity. The improved physical and metallurgical properties first given above are attributed to the invention claimed herein. Vacuum pressure levels are selected with reference to the apparent volatility of alloy constituents at the metal temperature involved and so as to preclude alloying constituent depletion due to processing requirements. More specifically, a vacuum environment of 1 10- mm. Hg has been determined to be unsatisfactory in at least one instance wherein the aluminum alloy zinc content was undesirably reduced from 5.5% to 0.2%.
Alsoby way of example, a casting having an aircraft elevator fitting configuration was cast in an alloy whose melt composition (average) consisted of 1.47% copper, 5.62% zinc,-2.6l% magnesium, 0.2% titanium, 0.16% beryllium, O.l% manganese, O.l% chromium, 0.1% iron, 0.08% silicon, and the balance aluminum, using the pre-heat-treatment melting, pouring, and directional solidification steps disclosed in the cross-reference application for United States patent. After conventional heat-treating in an argon atmosphere at 860 F. for 72 hours followed by quenching and conventional accelerated aging. Coupons cut from the so-processed casting were found to have ultimate tensile strengths from 58,900 p.s.i. to 70,600 p.s.i., elongations from 1.4% to 4.1%, and hardnesses (average) from R 78 to R 89. One other coupon from the casting was subjected to solution and homogenization heat-treating as specified above in the description of this invention for an additional 23 hours at 860 F. using a vacuum of 2 10- mm. Hg. After water-quenching and aging at 250 F. for 24 hours, the coupon was found to have an ultimate tensile strength of 92,200 p.s.i., a 3% elongation, and an average hardness of R 82.5.
What is claimed is:
1. A method of heat treating a precipitation hardenable aluminum alloy to develop improved physical and metallurgical properties, comprising the steps of:
(a) heating said alloy in a non-heat-treated solidified condition at a temperature in the temperature range from the alloy solidus temperature to the alloy solid solubility limit temperature and in a vacuum environment at a pressure above the pressure of alloying element depletion by vaporization at temperature a sufiicient time to dissolve second phase precipitates contained in said alloy and to compositionally homogenize said alloy.
(b) cooling said heated alloy at a rate sufficient to obtain a non-equilibrium metallurgical structure, and
(c) precipitation hardening said heated and cooled alloy by aging to develop improved physical and metallurgical properties therein.
2. The invention defined by claim 1, wherein said heating is continued for approximately 24 hours per 0.1" of alloy thickness.
3. The invention defined by claim 1, wherein said vacuum environment is at a pressure of approximately 2 10- mm. Hg absolute.
4. The invention defined by claim 3, wherein said heating is continued for approximately 24 hours per 0.1 of alloy thickness.
References Cited UNITED STATES PATENTS 1,996,379 4/1935 Keller 14816 2,221,526 11/1940 Sampson 148l59 2,995,479 8/1961 Cochran et al. 148l3.1 3,084,080 4/1963 Hunter et al. 148-13.1X
OTHER REFERENCES Chemical Abstracts, vol. 67, 1967, Abstract No. 46505(e).
CHARLES N. LOVELL, Primary Examiner
US715527A 1968-03-13 1968-03-25 Aluminum alloy heat-treating Expired - Lifetime US3598663A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US71267468A 1968-03-13 1968-03-13
US71552768A 1968-03-25 1968-03-25

Publications (1)

Publication Number Publication Date
US3598663A true US3598663A (en) 1971-08-10

Family

ID=27108868

Family Applications (1)

Application Number Title Priority Date Filing Date
US715527A Expired - Lifetime US3598663A (en) 1968-03-13 1968-03-25 Aluminum alloy heat-treating

Country Status (1)

Country Link
US (1) US3598663A (en)

Similar Documents

Publication Publication Date Title
US8409374B2 (en) Heat treatment of aluminium alloy high pressure die castings
US3219491A (en) Thermal treatment of aluminum base alloy product
JP6656013B2 (en) Low thermal expansion cast steel product and method of manufacturing the same
US3346370A (en) Aluminum base alloy
IL46384A (en) Heat treatment of aluminium alloys
KR101965418B1 (en) Heat treatment method of aluminum alloy
US6074501A (en) Heat treatment for aluminum casting alloys to produce high strength at elevated temperatures
US3698965A (en) High conductivity,high strength copper alloys
Girgis et al. On the elevated temperature, Tensile properties of Al-Cu cast alloys: Role of heat treatment
US3346371A (en) Aluminum base alloy
Lee et al. Grain-refined AZ92 alloy with superior strength and ductility
US3598663A (en) Aluminum alloy heat-treating
US3923555A (en) Processing copper base alloys
US3366476A (en) Aluminum base alloy
US2798827A (en) Method of casting and heat treating nickel base alloys
JPS5893860A (en) Manufacture of high strength copper alloy with high electric conductivity
US2829973A (en) Magnesium base alloys
US3346372A (en) Aluminum base alloy
US2185452A (en) Method of heat treating magnesium base alloys
US3574001A (en) High conductivity copper alloys
US3556872A (en) Process for preparing aluminum base alloys
US3573110A (en) Process for obtaining high conductivity copper alloys
US2022686A (en) Aluminum alloy casting and method of making the same
US3346377A (en) Aluminum base alloy
US2263823A (en) Method of producing and treating aluminum alloy castings

Legal Events

Date Code Title Description
AS Assignment

Owner name: GREENWALD, JOAN K. (SURVIVING SPOUSE)

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:GREENWALD, JOAN K., EXECUTOR OF HERBERT GREENWALD, JR.;REEL/FRAME:004558/0478

Effective date: 19860524