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WO1992019781A1 - Procede d'amelioration par degazage de la resilience de zirconium obtenu par la voie de la metallurgie des poudres et contenant des alliages aluminium-lithium - Google Patents

Procede d'amelioration par degazage de la resilience de zirconium obtenu par la voie de la metallurgie des poudres et contenant des alliages aluminium-lithium Download PDF

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Publication number
WO1992019781A1
WO1992019781A1 PCT/US1992/003171 US9203171W WO9219781A1 WO 1992019781 A1 WO1992019781 A1 WO 1992019781A1 US 9203171 W US9203171 W US 9203171W WO 9219781 A1 WO9219781 A1 WO 9219781A1
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WIPO (PCT)
Prior art keywords
ranges
powder
degassing
temperature
rapidly solidified
Prior art date
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Ceased
Application number
PCT/US1992/003171
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English (en)
Inventor
Jerry C. Lasalle
Derek Raybould
Santosh K. Das
Edward V. Limoncelli
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.)
Honeywell International Inc
Original Assignee
AlliedSignal Inc
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Filing date
Publication date
Application filed by AlliedSignal Inc filed Critical AlliedSignal Inc
Publication of WO1992019781A1 publication Critical patent/WO1992019781A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • 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

  • This invention relates to rapidly solidified powder metallurgy aluminum-lithium-zirconium-X alloys, and, in particular, to a process for developing enhanced toughness through temperature control during powder degassing.
  • Aluminum-lithium alloys are increasingly important materials for lightweight high stiffness applications such as aerospace components. Rapidly solidified aluminum-lithium alloys having reduced density and improved mechanical properties are disclosed in copending U.S. Pat. Appln. Ser. No. 478,306, filed February 12, 1990. Those are defined by the formula Al jj aiLi g Cu jj Mg p Zr- j wherein "a” ranges from about 2.1 to 3.4 wt%, "b” ranges from about 0.5 to 2.0 wt%, “c” ranges from about 0.2 to 2.0 wt% and “d” ranges from greater than about 0.6 to 1.8 wt%, the balance being aluminum.
  • Forgings produced from these rapidly solidified aluminum lithium alloys have significantly improved mechanical properties compared with forgings produced using conventional ingot aluminum lithium alloys.
  • the properties of forgings produced from a similar alloy but having somewhat lower zirconium have been reviewed by Kim, Raybould, Bye, and Das, Proc. Conf. Al-Li V, (1989), pg. 123 and by Quist, Bevers and Narayanan, Proc. Conf. Al-Li V, (1989), pg. 1695.
  • Quist et al. who represent the perspective of the aerospace industry, have stated that further improvements in the strength-toughness combination are needed before these alloys can find widespread use in aerospace components. Production of rapidly solidified aluminum lithium alloys can be divided into several steps.
  • the alloy is rapidly solidified by melt spinning into ribbon, which is thereafter pulverized into powder.
  • the second step comprises degassing the powder and consolidation thereof into a bulk piece.
  • the consolidated article is extruded and/or forged into a useful shape.
  • the fourth and final step comprises heat treating the alloy to optimizing the desired strength and ductility.
  • the present invention is directed to the degassing step of the process and provides a method whereby certain degassing parameters, especially the degassing temperature, is controlled to markedly improve the final toughness of the alloy.
  • certain degassing parameters especially the degassing temperature
  • the process of the present invention produces Al-Li containing material having a significant strength-toughness improvement.
  • the degassing treatment is believed to produce a more thorough removal of contaminants on the powder surface, leading to improved bonding of the powder particles.
  • the surface contaminants subject to removal by the process of the present invention are produced by a variety of gaseous species typically present in the ambient atmosphere, including oxygen, hydrogen, moisture, carbon monoxide and carbon dioxide.
  • These gaseous species are adsorbed on the surface of the metal and may react with the aluminum, lithium, and/or magnesium present in the alloy to form surface compounds which prevent complete bonding of the 10 powder during consolidation.
  • these surface contaminants reduce toughness and ductility by preventing thorough metal-metal contact between the particles. The film thus prevents adequate bonding between the powder 5 particles.
  • Surface contaminants may also be present as discrete inclusions, which reduce mechanical properties by providing sites for void/crack nucleation during deformation. In accordance with the present invention, surface contamination is 20 minimized by degassing the alloy powder under vacuum at a temperature in excess of 450°C.
  • Aluminum lithium alloys are unique as compared with 25 other aluminum alloys and other metallic systems.
  • Aluminum lithium alloys differ with other metallic systems because of the strong chemical affinity of lithium for chemical species such as oxygen, hydrogen, water and carbonates.
  • Q temperatures ranging between about 200°C and 440°C
  • aluminum lithium alloys form a reactive compound known as the ⁇ phase.
  • the ⁇ phase compound described by the stoichiometric formula Al-Li, has a strong tendency to adsorb the aforementioned chemical ,-. species.
  • zirconium containing Al-Li alloys Subjecting the zirconium containing Al-Li alloys to temperatures at or beyond 450°C will dissolve the ⁇ phase into the aluminum solid solution thereby liberating these adsorbed contaminants.
  • the presence of Al 3 Zr reduces planar slip during deformation and results in an overall improvement in the strength-toughness combination.
  • the strength-toughness improvement is particularly enhanced for alloys in which the zirconium content is greater than .6 wt%, and most preferably ranges from about 0.8 wt% to about 1.0 wt%.
  • Such preferred ranges of zirconium are particularly well suited to achieve the strength-toughness enhancement since they produce, upon rapid solidification, a sufficient amount of Ll 2 Al 3 Zr to prevent planar slip.
  • Zirconium levels beyond 1.0% further homogenize slip, however, it becomes more difficult to suppress the formation of the equilibrium tetragonal Al 3 Zr phase at greater zirconium levels. This tetragonal phase is detrimental to toughness.
  • Articles consolidated from the Al-Li alloy powder of the invention have ultimate tensile strength ranging from about 75 to 80 ksi, tensile elongation ranging from about 5 to 8% and T-L notched impact toughness ranging from about 100 to 150 in -lb/in 2 .
  • Figure 1 is a mass spectrograph showing the evolution of gaseous species vs. temperature of
  • Figure 2 is a mass spectrograph showing the evolution of gaseous species vs. temperature Al-2.6Li-l.0Cu-0.5Mg-0.6Zr powder heated in a vacuum after first being held in vacuum at 300°C for several hours.
  • the present invention provides a process for removal of contaminants adsorbed on the surface of a rapidly solidified zirconium containing aluminum lithium alloy powder consisting essentially of the formula
  • A1 bal Li a Cu b Mg c Zr d wnere i n " a " ranges from about 2.1 to 3.4 wt%
  • b M ranges from about 0.5 to 2.0 wt%
  • c ranges from about 0.2 to 2.0 wt%
  • d ranges from greater than about 0.6 to 1.8 wt%, the balance being aluminum.
  • Production of rapidly solidified aluminum lithium alloys described by the above formula can be divided into several steps.
  • the first step the alloy is rapidly solidified by melt spinning into ribbon, which is then pulverized into powder.
  • the second step comprises degassing the powder and consolidating it into a bulk piece.
  • the consolidated article is extruded or forged into a useful shape.
  • the fourth and final step comprises subjecting the shaped article to a heat treatment to optimize the desired combination of strength and ductility.
  • the present invention specifically addresses the degassing step which occurs prior to consolidation of the powder into a bulk component. Surface contaminants are removed via a process known as degassing in which the powder is heated in vacuum to drive volatile chemical species adsorbed on the surface of the powder. Subsequently, material is consolidated while still under vacuum by being subjected to a combination of high temperature and pressure. Degassing of the powder has been employed in connection with a variety of powder metallurgical alloys.
  • Aluminum lithium powders differ from conventional powders composed of aluminum and other metals in that the presence of lithium makes the powder significantly more reactive to contaminants which are present in the ambient atmosphere such as oxygen, moisture, CO, and CC «2.
  • aluminum lithium alloys form a reactive compound known as the ⁇ phase.
  • Such a compound, consisting of the stoichiometric formula Al-Li, has a strong tendency to adsorb the aforementioned gaseous species.
  • Powder made from a rapidly solidified alloy having a composition of Al-2.6Li-l.0Cu-0.5Mg-0.6Zr was placed in vacuum in a mass spectrometer and heated at a constant rate to about 600°C while the gas evolution was monitored as a function of temperature. Two peaks in the gas evolution are observed, one near approximately 200°C and one near approximately 450°C. Beyond 450°C, the gas concentration drops to a constant background level. The analysis indicates that a temperature of approximately 450°C is required for good removal of powder surface contaminants.
  • Powder made from a rapidly solidified alloy having a composition of Al-2.6Li-l.0Cu-0.5Mg-0.6Zr was placed in vacuum and held at a temperature of 300°C for several hours, cooled to room temperature, and heated at a constant rate to about 600°C while the gas evolution was monitored as a function of temperature.
  • the disappearance of the first peak observed in Example 1 indicates that a thorough removal of contaminants volatile at 300°C was obtained.
  • the continued presence of the peak near 450°C indicates that this temperature must be obtained for thorough removal of the surface contaminants and that extended periods of time spent at lower temperatures are not adequate to degas these components.
  • the gas concentration drops to a constant background level. The analysis indicates that a temperature of approximately 450°C is required for good removal of powder surface contaminants.
  • EXRMgLg 3 Consolidated pieces made from rapidly solidified Al-2.6Li-l.0Cu-0.5Mg-0.6Zr (wt%) powder degassed at either 200°C or 480°C were analyzed for impurities, listed in Table I.
  • Rectangular extrusions were made from rapidly solidified Al-2.6Li-l.0Cu-0.5Mg-0.6Zr (wt%) powder and Al-2.6Li-l.0Cu-0.5Mg-l.0Zr which was placed in a 10" diameter can and degassed at either 200 ⁇ C or 480 ⁇ C prior to being vacuum sealed within the can. Subsequently the cans were compacted, the can skin machined away, and the remaining billet extruded into l"x4" rectangular slabs. The extrusions were next solutionized at 540°C for 2 hrs., ice water quenched, and aged at 135°C for 16 hrs.
  • the Al-2.6Li-l.0Cu-0.5Mg-0.6Zr degassed at 480°C has an ultimate tensile strength 5 ksi greater than the degassed at 200°C. Both tensile elongation and notched impact toughness double, increasing from 3.3 to 5.3% and 55 to 100 in-lb/in 2 , respectively. This clearly illustrates the improvement in mechanical properties obtainable through employment of degassing temperatures beyond about 450 ⁇ C in material produced from degassed cans.
  • the Al-2.6Li-l.0Cu-0.5Mg-0.6Zr degassed at 480°C has elongation and toughness substantially equivalent to the 0.6Zr alloy while having a 6 ksi improvement in yield strength.
  • the overall strength-toughness combination is significantly greater for higher Zr containing alloys degassed at temperatures of about 480 ⁇ C.
  • Rectangular extrusions were made from rapidly solidified Al-2.6Li-l.0Cu-0.5Mg-0.6Zr (wt%) powder which was degassed in-situ while vacuum hot pressing into 4.5" diameter billets which were subsequently extruded into 3/8"x21/4" rectangular slabs. Thermal treatment and mechanical property characterization were identical to that of Example 4. The resulting data is listed in Table III.
  • Rectangular extrusions were made from rapidly solidified Al-2.4Li-l.0Cu-0.5Mg-l.0Zr (wt%) powder which was degassed in situ and vacuum hot pressed into 4.5" diameter billets, which were subsequently extruded into 3/8"x21/4" rectangular slabs. Thermal treatment and mechanical property characterization were identical to that of Example 4. The resulting data is listed in Table IV.
  • the tensile strengths are substantially the same for Al-2.6Li-l.0Cu-0.5Mg-0.6Zr and Al-2.4Li-l.0Cu-0.5Mg-l.0Zr, while the tensile elongation and notched impact toughness are slightly greater for the Al-2.4Li-l.0Cu-0.5Mg-l.0Zr alloy.
  • the additional Zr has resulted in an overall higher strength toughness combination, despite the fact that - li ⁇ the lower Li level of 2.4Li would be expected to have reduced the strength.

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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)

Abstract

Zirconium rapidement solidifié contenant une poudre d'alliage aluminium-lithium répondant principalement à la formule AlbalLiaCubMgcZrd dans laquelle 'a' varie de 2,1 à 3,4 pourcent en poids, 'b' varie d'environ 0,5 à 2,0 pourcent en poids, 'c' varie de 0,2 à 2,0 pourcent en poids et 'd' varie de plus de 0,6 environ à 1,8 pourcent en poids, le solde étant de l'aluminium. La poudre est dégazée sous vide à une température d'au moins 450 °C environ. Les composants solidifiés obtenus à partir de la poudre présentent une haute résistance à la traction, un fort allongement, ainsi qu'une excellente résilience.
PCT/US1992/003171 1991-04-29 1992-04-15 Procede d'amelioration par degazage de la resilience de zirconium obtenu par la voie de la metallurgie des poudres et contenant des alliages aluminium-lithium Ceased WO1992019781A1 (fr)

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US69283891A 1991-04-29 1991-04-29
US692,838 1991-04-29

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993017138A1 (fr) * 1992-02-20 1993-09-02 Allied-Signal Inc. Alliages d'aluminium-lithium contenant du zirconium solidifies rapidement pour roues de trains d'atterrissage d'avions

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3954458A (en) * 1973-11-12 1976-05-04 Kaiser Aluminum & Chemical Corporation Degassing powder metallurgical products
EP0158769A1 (fr) * 1984-02-29 1985-10-23 Allied Corporation Alliage d'aluminium à faible densité
EP0180144A1 (fr) * 1984-10-23 1986-05-07 Inco Alloys International, Inc. Alliages d'aluminium renforcés par dispersion
JPS6217144A (ja) * 1985-07-15 1987-01-26 Alum Funmatsu Yakin Gijutsu Kenkyu Kumiai Ａｌ−Ｌｉ合金の製造法
EP0279941A2 (fr) * 1987-02-25 1988-08-31 Vereinigte Aluminium-Werke Aktiengesellschaft Procédé et installation pour la préparation par métallurgie des poudres d'ébauches en aluminium sans soufflures et à faible teneur en hydrogène et oxyde

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3954458A (en) * 1973-11-12 1976-05-04 Kaiser Aluminum & Chemical Corporation Degassing powder metallurgical products
EP0158769A1 (fr) * 1984-02-29 1985-10-23 Allied Corporation Alliage d'aluminium à faible densité
EP0180144A1 (fr) * 1984-10-23 1986-05-07 Inco Alloys International, Inc. Alliages d'aluminium renforcés par dispersion
JPS6217144A (ja) * 1985-07-15 1987-01-26 Alum Funmatsu Yakin Gijutsu Kenkyu Kumiai Ａｌ−Ｌｉ合金の製造法
EP0279941A2 (fr) * 1987-02-25 1988-08-31 Vereinigte Aluminium-Werke Aktiengesellschaft Procédé et installation pour la préparation par métallurgie des poudres d'ébauches en aluminium sans soufflures et à faible teneur en hydrogène et oxyde

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 11, no. 193 (C-430)20 June 1987 & JP,A,62 017 144 ( ALUM FUNMATSU YAKIN GIJUTSU KENKYU KUMIAI ) 26 January 1987 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993017138A1 (fr) * 1992-02-20 1993-09-02 Allied-Signal Inc. Alliages d'aluminium-lithium contenant du zirconium solidifies rapidement pour roues de trains d'atterrissage d'avions

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