EP0035602B1 - Process for the production of a copper, zinc and aluminium base memory alloy by powder metallurgy technique - Google Patents

Process for the production of a copper, zinc and aluminium base memory alloy by powder metallurgy technique Download PDF

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EP0035602B1
EP0035602B1 EP80200186A EP80200186A EP0035602B1 EP 0035602 B1 EP0035602 B1 EP 0035602B1 EP 80200186 A EP80200186 A EP 80200186A EP 80200186 A EP80200186 A EP 80200186A EP 0035602 B1 EP0035602 B1 EP 0035602B1
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powder
weight
copper
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stream
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French (fr)
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EP0035602A1 (en
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Keith Dr. Melton
Olivier Dr. Mercier
Helmut Dr. Riegger
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BBC Brown Boveri AG Switzerland
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BBC Brown Boveri AG Switzerland
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Priority to EP80200186A priority Critical patent/EP0035602B1/en
Priority to DE8080200186T priority patent/DE3068396D1/en
Priority to DE19813103882 priority patent/DE3103882A1/en
Priority to JP56500752A priority patent/JPS57500512A/ja
Priority to PCT/CH1981/000024 priority patent/WO1981002587A1/en
Priority to US06/320,966 priority patent/US4398969A/en
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    • 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
    • C22F1/006—Resulting in heat recoverable alloys with a memory effect
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
    • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
    • C22C32/0021—Matrix based on noble metals, Cu or alloys thereof

Definitions

  • the workpiece was then cut into 2 round hammer passes at a temperature of 920 ° C to 18 or 16 mm Reduced diameter and homogenized in a stream of argon at 940 ° C for 1 h. This was followed by two round hammer punches at 920 ° C, so that the rod finally had a diameter of 13 mm. After homogenization again for 1 h at 940 ° C., the rod was rolled down in several successive hot rolling operations, each with a 20-25% reduction in cross section, to form a strip 1.6 mm thick and 18 mm wide. After a final annealing at 960 ° C. for 12 minutes, the strip was quenched in water. The density of the matrix of the finished tape was 99.6%.
  • thermomechanical processing which can consist of hot pressing, hot extrusion, hot forging, hot rolling, hot drawing and / or hot round hammering, should be carried out at temperatures between 700 and 1 000 ° C, as well as the intermediate homogenization in the inert gas stream (intermediate annealing) at least 700 ° C for at least 30 min.
  • the final annealing in a stream of argon is carried out at temperatures between 700 and 1 050 ° C. ( ⁇ -mixed crystal region) for 10 to 15 minutes and the workpiece is then immediately quenched in water.

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  • Engineering & Computer Science (AREA)
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  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
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  • Physics & Mathematics (AREA)
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  • Crystallography & Structural Chemistry (AREA)
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Description

Die Erfindung geht aus von einem Verfahren zur pulvermetallurgischen Herstellung einer Gedächtnislegierung nach der Gattung des Anspruchs 1.The invention relates to a method for the powder metallurgical production of a memory alloy according to the preamble of claim 1.

Gedächtnislegierungen auf der Basis des Systems Cu/Zn/AI sind bekannt und in verschiedenen Veröffentlichungen beschrieben worden (z. B. US-PS 3 783 037). Derartige Gedächtnislegierungen, die dem allgemeinen Typ mit der β-Hochtemperaturphase angehören, werden allgemein schmelzmetallurgisch hergestellt.Memory alloys based on the Cu / Zn / AI system are known and have been described in various publications (e.g. US Pat. No. 3,783,037). Such memory alloys, which belong to the general type with the β high-temperature phase, are generally produced by melt metallurgy.

Beim Giessen dieser Legierungen wird in der Regel ein grobkörniges Gefüge erhalten, welches durch die anschliessende Glühung im Bereich der β-Mischkristalle durch Kornwachstum noch weiter vergröbert wird und durch thermomechanische Behandlung nicht mehr rückgängig gemacht werden kann. Dementsprechend sind die mechanischen Eigenschaften, vor allem die Dehnung und Kerbzähigkeit solcherweise hergestellter Gedächtnislegierungen verhältnismässig schlecht und ihr Anwendungsbereich begrenzt.When these alloys are cast, a coarse-grained structure is generally obtained, which is further coarsened by grain growth due to the subsequent annealing in the region of the β mixed crystals and cannot be reversed by thermomechanical treatment. Accordingly, the mechanical properties, especially the elongation and notch toughness of memory alloys produced in this way are relatively poor and their field of application is limited.

Es besteht daher ein Bedürfnis, diese Gedächtnislegierungen metallurgisch und verfahrenstechnisch derart zu verbessern, dass für sie weitere praktische Anwendungsgebiete erschlossen werden können.There is therefore a need to improve these memory alloys metallurgically and procedurally in such a way that further practical fields of application can be opened up for them.

Es ist bereits vorgeschlagen worden, Gedächtnislegierungen des Typs Cu/Zn/AI pulvermetallurgisch, ausgehend von fertigen, der Endzusammensetzung entsprechenden Ausgangslegierungen herzustellen (z. B. M. Follon, E. Aernoudt, Powdermetallurgically processed shape-memory alloys, 5th European Symposium on Powder Metallurgy, Stockholm 1978, S. 275-281. Dabei wird das fertige Pulver eingekapselt, kaltverdichtet, warmverdichtet und stranggepresst. Diese Methode wird jedoch nicht allen Forderungen der Praxis gerecht und die Fertigkörper lassen in ihren mechanischen Eigenschaften oft zu wünschen übrig.It has already been proposed to manufacture memory alloys of the Cu / Zn / AI type by powder metallurgy, starting from finished starting alloys corresponding to the final composition (e.g. BM Follon, E. Aernoudt, Powdermetallurgically processed shape-memory alloys, 5th European Symposium on Powder Metallurgy, Stockholm 1978, pp. 275-281, where the finished powder is encapsulated, cold-compressed, hot-compressed and extruded, but this method does not meet all practical requirements and the mechanical properties of the finished product often leave something to be desired.

Weiterhin ist auch dem Dokument DE-A1-2856082 das oben beschriebene Verfahren zur Herstellung von Gedächtnislegierungen des Typs Cu/Zn/AI zu entnehmen. Die dabei erzeugte Legierung hat ein feinkörniges Matrixgefüge mit Korngrössen zwischen 20 und 30 µm, wobei geringe Mengen von Al2O3 in der Matrix dispergiert erscheinen, welche vermutlich als Kornwachstumsinhibitoren wirken.Furthermore, document DE-A1-2856082 also shows the process described above for producing memory alloys of the Cu / Zn / AI type. The alloy produced in this way has a fine-grained matrix structure with grain sizes between 20 and 30 μm, small amounts of Al 2 O 3 appearing dispersed in the matrix, which presumably act as grain growth inhibitors.

Der Erfindung liegt die Aufgabe zugrunde, ein Herstellungsverfahren für Gedächtnislegierungen auf der Basis von Kupfer, Zink und Aluminium anzugeben, das zu dichten, kompakten Körpern mit guten mechanischen Eigenschaften und gleichzeitig zu genau reproduzierbaren Werten der Umwandlungstemperatur und anderen mit dem Gedächtniseffekt zusammenhängenden Grössen führt.The invention has for its object to provide a manufacturing method for memory alloys based on copper, zinc and aluminum, which leads to dense, compact bodies with good mechanical properties and at the same time to exactly reproducible values of the transition temperature and other variables related to the memory effect.

Diese Aufgabe wird erfindungsgemäss durch die Merkmale des Anspruchs 1 gelöst.According to the invention, this object is achieved by the features of claim 1.

Der Kern der Erfindung besteht darin, weder von Elementarpulvern noch von einem der Endlegierung entsprechenden Ausgangspulver auszugehen, sondern eine Mischung aus vorlegierten Pulvern und speziell zusammengesetzten Pulvermischungen zu benutzen und diese Pulver mit geeigneten Metalloxydpulvern mechanisch zu legieren. Damit kann die erforderliche Duktilität bei weitgehender Freiheit bezüglich Zusammensetzung dem Verarbeitungsprozess optimal angepasst werden. Die Korngrösse der Kristallite des fertigen Körpers kann weitgehend vorausbestimmt werden. Ein Kornwachstum wird durch die gezielt eingebrachten Dispersoide vermieden. Zusammenhängende, die Homogenisierung behindernde und die mechanischen Eigenschaften beeinträchtigende Oxydhäute sind infolgedessen nicht zu befürchten.The essence of the invention is not to start from elementary powders or from a starting powder corresponding to the final alloy, but to use a mixture of pre-alloyed powders and specially composed powder mixtures and to mechanically alloy these powders with suitable metal oxide powders. This allows the required ductility to be optimally adapted to the processing process with extensive freedom in terms of composition. The grain size of the crystallite of the finished body can largely be predetermined. Grain growth is avoided by the specifically introduced dispersoids. As a result, coherent oxide skins that hinder homogenization and impair mechanical properties are not to be feared.

Die Erfindung wird anhand der nachfolgenden Ausführungsbeispiele beschrieben :

  • Ausführungsbeispiel I
The invention is described using the following exemplary embodiments:
  • Embodiment I

Es wurde ein Rundstab aus einer Gedächtnislegierung folgender Endzusammensetzung der Matrix hergestellt:

Figure imgb0001
A round rod was made from a memory alloy of the following final composition of the matrix:
Figure imgb0001

Die Legierung soll ausserdem 2 Gew.-% Yttriumoxyd als Dispersoid enthalten.The alloy is also said to contain 2% by weight yttrium oxide as a dispersoid.

Als Ausgangsmaterialien wurden folgende Pulver verwendet :

  • Pulver A : Messing : 60 Gew.-% Cu ; 40 Gew.-% Zn, erschmolzen, atomisiert ; Korngrösse 10-200 µ. Hersteller Baudier.
  • Pulver B : Reinaluminium + Reinkupfer: 99,5 Gew.-% AI ; 0,5 Gew.-% Cu, Korngrösse 23-28 µ. Hersteller Alcoa.
  • Pulver C : Reinkupfer : 100 Gew.-% Cu Korngrösse 0-44 µ. Hersteller Baudier
  • Pulver D : Yttriumoxyd : 100 Gew.-% Y203 Korngrösse < 1 µ.
The following powders were used as starting materials:
  • Powder A: brass: 60% by weight of Cu; 40% by weight of Zn, melted, atomized; Grain size 10-200 µ. Manufacturer Baudier.
  • Powder B: pure aluminum + pure copper: 99.5% by weight Al; 0.5% by weight of Cu, grain size 23-28 µ. Manufacturer Alcoa.
  • Powder C: pure copper: 100% by weight Cu grain size 0-44 µ. Manufacturer Baudier
  • Powder D: yttrium oxide: 100% by weight Y 2 0 3 grain size <1 µ.

Folgende Einwaage wurde während 10 h unter Toluol im Attritor gemischt, gemahlen und mechanisch legiert :

Figure imgb0002
The following sample was mixed, ground and mechanically alloyed under toluene in the attritor for 10 h:
Figure imgb0002

Zur Verflüchtigung des Toluols wurde die Pulvermischung getrocknet und anschliessend davon 250 g in einen Gummischlauch von 20 mm Innendurchmesser abgefüllt und bei einem Druck von 3 000 bar isostatisch zu einem Zylinder von 18 mm Durchmesser und 240 mm Höhe verpresst. Der Grünling wurde im Wasserstoffstrom bei einer Temperatur von 930 °C während 1 1/2 h reduziert und vorgesintert und anschliessend im Argonstrom bei einer Temperatur von 960 °C während 18 h fertiggesintert. Der rohe Sinterkörper wurde auf einen Durchmesser von 17 mm abgedreht, in ein weichgeglühtes Kupferrohr von 20 mm Aussendurchmesser eingeführt und durch Abdecken der Enden mittels Stöpsel und Verlöten unter Argonatmosphäre vollständig eingekapselt. Das derart gebildete Werkstück wurde nun abwechslungsweise einer thermomechanischen Bearbeitung und einer Homogenisierungsglühung im Argonstrom während je 1 h bei 940 °C unterworfen. Im vorliegenden Fall bestand die thermomechanische Bearbeitung in einem Rundhämmern bei 940 °C, wobei im 1. Rundhämmerstich der Durchmesser des Stabes auf 18 mm und bei jedem weiteren Stich um je 2 mm reduziert wurde. Dabei wurde so vorgegangen, dass auf je 2 thermomechanische Operationen eine Homogenisierungsglühung folgte. Der auf 8 mm Durchmesser heruntergehämmerte Stab wurde schliesslich einer abschliessenden Glühung im Argonstrom während 15 min bei einer Temperatur von 920 °C unterworfen und unmittelbar daraufhin in Wasser abgeschreckt. Die Prüfung ergab für die Matrix eine Dichte von 99,3-99,7 % des theoretischen Wertes.In order to volatilize the toluene, the powder mixture was dried and then 250 g of it were filled into a rubber tube with an inner diameter of 20 mm and pressed isostatically at a pressure of 3,000 bar to a cylinder with a diameter of 18 mm and a height of 240 mm. The green body was reduced in a hydrogen stream at a temperature of 930 ° C. for 1 1/2 hours and presintered and then sintered in a stream of argon at a temperature of 960 ° C. for 18 hours. The raw sintered body was turned to a diameter of 17 mm, introduced into a soft-annealed copper tube with an outer diameter of 20 mm and completely encapsulated by covering the ends by means of plugs and soldering under an argon atmosphere. The workpiece formed in this way was then alternately subjected to thermomechanical processing and homogenization annealing in a stream of argon for 1 h at 940 ° C. In the present case, the thermomechanical processing consisted of round hammering at 940 ° C, the diameter of the rod being reduced to 18 mm in the first round hammering stitch and by 2 mm for each further stitch. The procedure was such that 2 thermomechanical operations were followed by homogenization annealing. The rod hammered down to 8 mm in diameter was finally subjected to a final annealing in a stream of argon for 15 minutes at a temperature of 920 ° C. and immediately quenched in water. The test showed a density of 99.3-99.7% of the theoretical value for the matrix.

Selbstverständlich kann der Zyklus thermomechanische Bearbeitung/Homogenisierung beliebig lang, bis zum Erreichen der endgültigen Form des Werkstückes fortgesetzt werden. Dabei ist bei Erreichen der theoretischen Dichte eine weitere Homogenisierung in der Regel nicht mehr notwendig.Of course, the cycle of thermomechanical machining / homogenization can be continued for as long as required until the final shape of the workpiece is reached. When the theoretical density is reached, further homogenization is generally no longer necessary.

Ausführungsbeispiel IIEmbodiment II

Es wurde ein Band aus einer Gedächtnislegierung folgender Endzusammensetzung der Matrix hergestellt:

Figure imgb0003
A tape was made from a memory alloy of the following final composition of the matrix:
Figure imgb0003

Die Legierung soll ausserdem 1 Gew.-% Yttriumoxyd als Dispersoid enthalten.The alloy should also contain 1% by weight of yttrium oxide as a dispersoid.

Die unter dem Beispiel I angegebenen Pulver wurden wie folgt eingewogen und während 8 h unter Aethylalkohol in einer Kugelmühle gemischt, gemahlen und mechanisch legiert :

Figure imgb0004
The powders given in Example I were weighed in as follows and mixed, ground and mechanically alloyed in a ball mill for 8 hours under ethyl alcohol:
Figure imgb0004

Nach der Verflüchtigung des Aethylalkohols wurden 240 g dieser Pulvermischung in ein weichgeglühtes Tombakrohr von 20 mm Innendurchmesser und 1,6 mm Wandstärke abgefüllt und durch Abdecken der Enden und Verlöten unter Argonatmosphäre vollständig eingekapselt. Hierauf wurde das Rohr samt Pulver bei einem Druck von 10000 bar isostatisch gepresst und der Pressling im Wasserstoffstrom bei einer Temperatur von 880°C während 2 h reduziert und vorgesintert und anschliessend im Argonstrom bei einer Temperatur von 840 °C während 22 h fertiggesintert. Daraufhin wurde das Werkstück in 2 Rundhämmerstichen bei einer Temperatur von 920 °C auf 18 bzw. 16 mm Durchmesser reduziert und während 1 h im Argonstrom bei 940 °C homogenisiert. Es folgten nochmals 2 Rundhämmerstiche bei 920 °C, so dass der Stab schliesslich einen Durchmesser von 13 mm hatte. Nach abermaliger Homogenisierung während 1 h bei 940 °C wurde der Stab in mehreren aufeinanderfolgenden Warmwalzoperationen mit jeweils 20-25 % Querschnittsabnahme zu einem Band von 1,6 mm Dicke und 18 mm Breite heruntergewalzt. Nach einer abschliessenden Glühung bei 960 °C während 12 min wurde das Band in Wasser abgeschreckt. Die Dichte der Matrix des fertigen Bandes betrug 99,6 %.After the volatilization of the ethyl alcohol, 240 g of this powder mixture were poured into a soft-annealed tombac tube with an inner diameter of 20 mm and a wall thickness of 1.6 mm and completely encapsulated by covering the ends and soldering under an argon atmosphere. The tube and powder were then isostatically pressed at a pressure of 10,000 bar and the compact was reduced and presintered in a stream of hydrogen at a temperature of 880 ° C. for 2 h and then sintered in a stream of argon at a temperature of 840 ° C. for 22 h. The workpiece was then cut into 2 round hammer passes at a temperature of 920 ° C to 18 or 16 mm Reduced diameter and homogenized in a stream of argon at 940 ° C for 1 h. This was followed by two round hammer punches at 920 ° C, so that the rod finally had a diameter of 13 mm. After homogenization again for 1 h at 940 ° C., the rod was rolled down in several successive hot rolling operations, each with a 20-25% reduction in cross section, to form a strip 1.6 mm thick and 18 mm wide. After a final annealing at 960 ° C. for 12 minutes, the strip was quenched in water. The density of the matrix of the finished tape was 99.6%.

Ausführungsbeispiel IIIEmbodiment III

Es wurde ein Vierkantstab aus einer Gedächtnislegierung folgender Endzusammensetzung der Matrix hergestellt :

Figure imgb0005
A square bar was produced from a memory alloy with the following final composition of the matrix:
Figure imgb0005

Die Legierung soll ausserdem 0,5 Gew.-% Titandioxyd als Dispersoid enthalten.The alloy should also contain 0.5% by weight of titanium dioxide as a dispersoid.

Die Pulver A, B, C und D* (100 % Titandioxyd) wurden wie folgt eingewogen und während 10 h unter Toluol in einem Attritor gemischt, gemahlen und mechanisch legiert :

Figure imgb0006
The powders A, B, C and D * (100% titanium dioxide) were weighed out as follows and mixed, ground and mechanically alloyed for 10 hours under toluene in an attritor:
Figure imgb0006

Nach dem Trocknen wurden 600 g dieser Pulvermischung in einen Gummischlauch von 50 mm Innendurchmesser abgefüllt und bei einem Druck von 10000 bar isostatisch zu einem Zylinder von 46 mm Durchmesser und 90 mm Höhe verpresst. Der Grünling wurde im Wasserstoff/Stickstoff-Strom bei einer Temperatur von 900 °C während 2 h reduziert und vorgesintert und anschliessend im Argonstrom bei einer Temperatur von 980 °C während 20 h fertiggesintert. Der rohe Sinterkörper wurde auf einen Durchmesser von 45 mm abgedreht, in den Rezipienten einer Strangpresse eingesetzt und bei einer Temperatur von 900 °C zu einem Vierkantstab quadratischen Querschnitts von 10 mm Kantenlänge verpresst. Das Reduktionsverhältnis (Querschnittsabnahme) betrug dabei 16: 1. Daraufhin wurde der Stab bei einer Temperatur von 980 °C während 30 min homogenisiert und anschliessend in 3 Stichen auf einer Warmziehbank bei einer Temperatur von 800 °C auf eine Kantenlänge von 7 mm heruntergezogen. Nach der abschliessenden Glühung bei 920 °C während 15 min im Argonstrom wurde der Stab in Wasser abgeschreckt. Die Dichte der Matrix des fertigen Stabes betrug 99,7 % des theoretischen Wertes.After drying, 600 g of this powder mixture were filled into a rubber tube with an inner diameter of 50 mm and pressed isostatically at a pressure of 10,000 bar to a cylinder with a diameter of 46 mm and a height of 90 mm. The green compact was reduced in a hydrogen / nitrogen stream at a temperature of 900 ° C. for 2 h and presintered and then sintered in a stream of argon at a temperature of 980 ° C. for 20 h. The raw sintered body was turned to a diameter of 45 mm, inserted in the recipient of an extrusion press and pressed at a temperature of 900 ° C. to a square bar with a square cross section and an edge length of 10 mm. The reduction ratio (reduction in cross-section) was 16: 1. The rod was then homogenized at a temperature of 980 ° C. for 30 minutes and then pulled down in 3 passes on a warming bench at a temperature of 800 ° C. to an edge length of 7 mm. After the final annealing at 920 ° C. for 15 minutes in a stream of argon, the rod was quenched in water. The density of the matrix of the finished rod was 99.7% of the theoretical value.

Die Erfindung ist nicht auf die in den Beispielen beschriebenen Grössen und Werte beschränkt. Ganz allgemein können die Pulverzusammensetzungen und die Partikelgrössen in folgenden Grenzen variiert und substituiert werden :

  • Pulver A: Vorlegierung Kupfer : 60-80 Gew.-% Aluminium : 0-1 Gew.-% Zink: Rest Partikelgrösse :10-200 µ
  • Pulver B : Vormischung und/oder Vorlegierung (Schmelzmetallurgisch oder mechanisch legiert) Aluminium : 95-99,5 Gew.-% Kupfer : 0,5-5 Gew.-% Partikelgrösse : 5-100 µ
  • Pulver C : Reines Metall Kupfer : 100 Gew.-% Partikelgrösse : 10-100 µ
  • Pulver D : Metalloxyde (Dispersoide) Yttriumoxyd : 0-100 Gew.-% Titandioxyd : 0-100 Gew.-%
The invention is not restricted to the sizes and values described in the examples. In general, the powder compositions and the particle sizes can be varied and substituted within the following limits:
  • Powder A: master alloy copper: 60-80% by weight aluminum: 0-1% by weight zinc: remainder particle size: 10-200 µ
  • Powder B: premix and / or pre-alloy (melt metallurgically or mechanically alloyed) aluminum: 95-99.5% by weight copper: 0.5-5% by weight particle size: 5-100 µ
  • Powder C: Pure metal copper: 100% by weight particle size: 10-100 µ
  • Powder D: metal oxides (dispersoids) yttrium oxide: 0-100% by weight titanium dioxide: 0-100% by weight

Selbstverständlich könnte das Pulver A auch anders zusammengesetzt sein, indem man z. B. elementares Zink beimischt. In Anbetracht des Abbrandes und der Verdampfung dieser Elemente ist dies jedoch in den meisten Fällen nicht zu empfehlen.Of course, the powder A could also be composed differently by z. B. elemental zinc admixed. In view of the burn-up and the evaporation of these elements, this is not recommended in most cases.

Die Pulvermischungen können sich in folgenden Grenzen bewegen :

Figure imgb0007
The powder mixtures can be within the following limits:
Figure imgb0007

Für das isostatische Pressen ist ein Druck von mindestens 3 000 bar erforderlich.A pressure of at least 3,000 bar is required for isostatic pressing.

Das Reduzieren und Vorsintern des Presslings kann zweckmässigerweise im Temperaturbereich von 700 bis 1 000 °C während mindestens 30 min im Wasserstoff- oder Wasserstoff/Stickstoff-Strom erfolgen. Das Sintern des Presslings muss oberhalb der Temperatur der eutektoiden Umwandlung, d. h. bei mindestens 700 °C während 10 h im Argonstrom durchgeführt werden, um ein möglichst homogenes Gefüge zu erzielen. Die thermomechanische Bearbeitung, welche in einem Warmpressen, Warmstrangpressen, Warmschmieden, Warmwalzen, Warmziehen und/oder Warm-Rundhämmern bestehen kann, soll bei Temperaturen zwischen 700 und 1 000 °C bewerkstelligt werden, des gleichen das dazwischengeschaltete Homogenisieren im Inertgasstrom (Zwischenglühen) bei mindestens 700 °C während mindestens 30 min. Das abschliessende Glühen im Argonstrom wird bei Temperaturen zwischen 700 und 1 050 °C (ß-Mischkristallgebiet) während 10 bis 15 min durchgeführt und das Werkstück sofort danach in Wasser abgeschreckt.The reduction and presintering of the compact can expediently take place in the temperature range from 700 to 1000 ° C. for at least 30 minutes in a stream of hydrogen or hydrogen / nitrogen. The sintering of the compact must be above the temperature of the eutectoid transformation, i.e. H. at least 700 ° C for 10 h in a stream of argon to achieve the most homogeneous structure possible. The thermomechanical processing, which can consist of hot pressing, hot extrusion, hot forging, hot rolling, hot drawing and / or hot round hammering, should be carried out at temperatures between 700 and 1 000 ° C, as well as the intermediate homogenization in the inert gas stream (intermediate annealing) at least 700 ° C for at least 30 min. The final annealing in a stream of argon is carried out at temperatures between 700 and 1 050 ° C. (β-mixed crystal region) for 10 to 15 minutes and the workpiece is then immediately quenched in water.

Für die meisten thermomechanischen Bearbeitungsarten ist es zweckmässig, das Material zuvor in eine duktile, mit ihm chemisch nicht reagierende metallische Hülle einzukapseln, die am Schluss der Formgebung als Oberflächenschicht in den meisten Anwendungsfällen mechanisch oder chemisch entfernt wird. Als Werkstoffe für die Hülle bieten sich vor allem weichgeglühte Metalle und Legierungen wie Kupfer, Kupferlegierungen und Weicheisen an. Das Einkapseln kann unmittelbar vor der thermomechanischen Bearbeitung erfolgen, indem der Sinterkörper zuvor eine mechanische Oberflächenbehandlung durch Abdrehen, Fräsen, Hobeln etc. erfährt, oder es kann das Pulver direkt statt in einen Gummi- oder Kunststoffschlauch in ein entsprechendes Rohr, eine Dose etc. eingefüllt werden.For most types of thermomechanical processing, it is advisable to encapsulate the material beforehand in a ductile metallic shell that does not chemically react with it, which is removed mechanically or chemically at the end of the shaping as a surface layer in most applications. Soft-annealed metals and alloys such as copper, copper alloys and soft iron are particularly suitable as materials for the casing. Encapsulation can take place immediately before the thermomechanical processing, in that the sintered body undergoes a mechanical surface treatment beforehand by turning, milling, planing, etc., or the powder can be filled directly into a suitable tube, a can, etc., instead of into a rubber or plastic tube will.

Durch das erfindungsgemässe pulvermetallurgische Verfahren sowie die danach erzeugten Dispersionslegierungen wird die Herstellung von Werkstücken aus einer Gedächtnislegierung des Cu/Zn/AI-Typs ermöglicht, welche gegenüber herkömmlich, d. h. schmelzmetallurgisch erzeugten Körpern ein feinkörniges Gefüge und eine hohe Reproduzierbarkeit ihrer physikalischen Kennwerte aufweisen. Die mechanischen Eigenschaften, insbesondere die Dehnung, Kerbzähigkeit und das Arbeitsvermögen derartiger Werkstücke sind bedeutend besser als diejenigen gegossener und/oder weiterhin warmgekneteter Körper. Damit wird diesem Legierungstyp ein weiteres Anwendungsgebiet erschlossen.The powder metallurgical process according to the invention and the dispersion alloys produced thereafter enable the production of workpieces from a memory alloy of the Cu / Zn / Al type, which is compared to conventional, i.e. H. bodies produced by melting metallurgy have a fine-grained structure and a high reproducibility of their physical characteristics. The mechanical properties, in particular the elongation, notch toughness and the working capacity of such workpieces are significantly better than those of cast and / or hot-kneaded bodies. This opens up a further area of application for this type of alloy.

Claims (3)

1. Process for the manufacture of a memory alloy by a powder-metallurgical route, this alloy being based on copper, zinc and aluminium, existing in the form of the ß phase, and possessing a fine-grained microstructure which is stable up to 950 °C, exhibits a crystallite diameter not exceeding 100 µ and contains at least one oxide dispersoid, finely distributed in the metal matrix in an amount equivalent to 0.5 to 2 per cent, by weight, of the total mass, the diameter of the dispersoid-particles being in the range from 0.001 to 1 µ, this process comprising the following steps :
a) Manufacture of a powder A, from a copper-rich prealloy containing 60 to 80 % by weight of Cu and 0 to 1 % by weight of Al, the balance being Zn, the particle size of this powder being in the range from 10 to 200 µ ; manufacture of a powder B, possessing a particle size in the range from 5 to 100 µ, by mixing and/or alloying 95 to 99.5 % by weight of aluminium powder with 0.5 to 5 % by weight of copper powder ; manufacture of a pure copper powder C, possessing a particle size in the range from 10 to 100 R ; manufacture of a Y203 or Ti02 powder, or a powder consisting of any desired mixture of these oxides, powder D, with a particle size in the range from 0.1 to 10 µ ;
b) Mixing of 0.5 to 15 % by weight of powder B, 0 to 80 % by weight of powder C, and 0.5 to 2 % by weight of powder D, the balance being powder A, in a ball mill or an attrition mill, under toluene, ethyl alcohol, or another organic solvent, for not less than 5 hours, at room temperature, followed by evaporation of the solvent ;
c) Isostatic pressing of the dried powder mixture, in a flexible tube, made of plastic or rubber, at a pressure of not less than 3 000 bar ;
d) Reduction and presintering of the compact produced in step c), in a stream of hydrogen or of a hydrogen/nitrogen mixture, at between 700 and 1 000 °C, for not less than 30 minutes ;
e) Sintering of the reduced and presintered compact, in a stream of argon, at not less than 700 °C, for not less than 10 hours ;
f) Thermomechanical working and homogenisation, performed in alternation, the working being carried out at between 700 and 1 000 °C and the homogenisation being performed in a stream of inert gas, at not less than 700 °C, for not less than 30 minutes ;
g) Final annealing, in a stream of argon, at between 700 and 1 050 °C, for 10 to 15 minutes, followed immediately by quenching in water.
2. Process according to Claim 1, characterised in that, before process-step f), the sintered workpiece is subjected to a surface treatment, of a mechanical nature, after which it is encased in a jacket composed of soft-annealed copper, iron, or a soft copper alloy.
3. Process according to Claim 2, characterised in that the mechanical surface treatment takes the form of a surface-machining operation, and the workpiece, thus machined, is inserted into a soft-annealed copper tube which is completely sealed by blanking-off the ends with plugs and solder-sealing under an argon atmosphere.
EP80200186A 1980-03-03 1980-03-03 Process for the production of a copper, zinc and aluminium base memory alloy by powder metallurgy technique Expired EP0035602B1 (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
EP80200186A EP0035602B1 (en) 1980-03-03 1980-03-03 Process for the production of a copper, zinc and aluminium base memory alloy by powder metallurgy technique
DE8080200186T DE3068396D1 (en) 1980-03-03 1980-03-03 Process for the production of a copper, zinc and aluminium base memory alloy by powder metallurgy technique
DE19813103882 DE3103882A1 (en) 1980-03-03 1981-02-05 "MEMORY ALLOY BASED ON COPPER, ZINC AND ALUMINUM AND METHOD FOR THE PRODUCTION THEREOF"
JP56500752A JPS57500512A (en) 1980-03-03 1981-03-02
PCT/CH1981/000024 WO1981002587A1 (en) 1980-03-03 1981-03-02 Memory allows with a copper,zinc and aluminum base and method for preparing them
US06/320,966 US4398969A (en) 1980-03-03 1981-03-02 Shape-memory alloy based on copper, zinc and aluminum and process for preparing it

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EP80200186A EP0035602B1 (en) 1980-03-03 1980-03-03 Process for the production of a copper, zinc and aluminium base memory alloy by powder metallurgy technique

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EP0035602A1 EP0035602A1 (en) 1981-09-16
EP0035602B1 true EP0035602B1 (en) 1984-07-04

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US6977017B2 (en) 2001-10-25 2005-12-20 Council Of Scientific & Industrial Research Cu-ZN-A1(6%) shape memory alloy with low martensitic temperature and a process for its manufacture
ES2276605B1 (en) * 2005-08-31 2008-05-16 Universidad Del Pais Vasco - Euskal Herriko Unibertsitatea A COMPOSITE METAL MATRIX MATERIAL BASED ON ALLOY POWDER WITH FORM MEMORY, ITS PROCESSING AND USE PROCEDURE.
US20130280120A1 (en) * 2010-04-23 2013-10-24 United States Department Of Energy Hard and Super-hard Metal Alloys and Methods for Making the Same
CN114107716B (en) * 2021-12-02 2022-05-03 合肥工业大学 Preparation method of copper-based composite material for electrical contact
CN115044794B (en) * 2022-06-08 2022-12-20 合肥工业大学 Cu- (Y) with excellent performance 2 O 3 -HfO 2 ) Alloy and preparation method thereof

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JPS57500512A (en) 1982-03-25
WO1981002587A1 (en) 1981-09-17
EP0035602A1 (en) 1981-09-16
US4398969A (en) 1983-08-16
DE3103882A1 (en) 1982-04-01
DE3068396D1 (en) 1984-08-09

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