Classifications

• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B3/00—Unidirectional demixing of eutectoid materials

Definitions

• the starting materials must have a grain size of more than approximately 0.1 mm.
• the materials are directionally demixed while using a temperature gradient of at least C. per cm. which is passed through the body at a rate which is less than or equal to the maximum demixing rate.
• the invention relates to a method of manufacturing bodies of lamellar composites by directionally demixing solid single-phase materials which demix discontinuously in two or more phases upon cooling.
• These single-phase materials may have a eutectoid composition or may consist of solid solutions.
• Lamellar composites are understood to mean materials whose grains consist of at least two phases in which at least one of the phases in at least one direction has a dimension which is relatively much larger than the dimensions in the other directions. These materials thus comprise both composites whose grains are built up from thin sheets of alternatively the one and the other phase and composites one phase of which consists of needles which are embedded in a different phase.
• Discontinuous demixing sometimes also referred to as cellular demixing, is understood to mean that the new phases are produced by nucleation and growth from the grain boundaries at which the composition of the transformed matrix remains uniform except for the incoherent boundary of the growing cell.
• Methods of directionally coagulating melts of mixtures of materials are known (see, for example, US. Pat. 3,124,452). Generally methods are used which are also employed in the manufacture of monocrystalline materials in which the molten material is allowed to cool off in a previously determined direction such as, for example, in the method according to Bridgman.
• An object of the present invention is to provide a method of manufacturing bodies of lamellar composites by directionally demixing solid singlephase materials which demix discontinuously in two or more phases upon cooling in such a manner that the lamellae in all grains are substantially parallel to the trans- 3,694,193 Patented Sept. 26, 1972 formation direction. It was found that this condition can be satisfied by a method which is characterized in that a single-phase material is directionally demixed whose grains have a diameter of not less than approximately 0.1 mm. while using a temperature gradient of at least 10 C. per cm. passed through the body at a rate which is less than or equal to the maximum rate of demixing.
• the maximum rate of the transformation front is different for each system, but may be experimentally determined in a simple manner. It was found in practice that the maximum rate of the transformation front is greater as the eutectoid temperature or the saturation temperature is higher. Usually the maximum rate lies between 10 and l0 -T cm. per hour wherein T is the eutectoid temperature in K. or the saturation temperature in K. Failure of the experiments which have become known in literature up till now is probably to be ascribed to the fact that one or more of the three mentioned criteria are not satisfied. No directional effect was found when, for example, the method Was used on the systems: 28 at. percent Zn, remainder Fe (solid solution), grain size approximately 50 11111.; 25 at.
• the method according to the invention may be performed by means of a technique which is comparable with the Bridgman technique in which the body is passed through a temperature gradient or in which the temperature gradient is moved relative to the body.
• the temperature gradients to be used may be obtained with comparatively simple standard apparatus.
• the external temperature gradient to be used is less than 450 C./cm.
• the temperature gradient is chosen to be so much greater as the grain diameter is smaller.
• the method may be used for reinforcing articles, for example, tools.
• the articles it is then possible to subject the articles to mechanical operations, for example, forging at the temperature above the transformation temperature (eutectoid temperature or the temperature at which saturation occurs) or at room temperature after previous tempering from a temperature above the transformation temperature and by subsequently giving the articles a greater strength by means of directional demixing.
• the method may alternatively be used to give articles certain magnetical, electrical and/ or optical properties.
• EXAMPLE I A quartz tube having a length of 10 cms. and an internal diameter of 0.4 cm. and an external diameter of 0.54 cm. was filled with a molten alloy of nickel and indium (55.5 at. percent In, remainder Ni),melting point approximately 950" C., eutectoid temperature 770 C. The alloy was heated for two hours at 1050 C. and it was subsequently coagulated by decreasing the temperature to approximately 850 C. After this treatment the grains had a diameter of between 0.5 and 3 mms. The alloyfilled tube was subsequently passed through a temperature gradient of 65 C. per cm. at a constant rate of 0.1 cm. per hour (Bridgman technique). The lamella distance in the directionally demixed body was 0.7 ,um.
• the lamellae in the grains were parallel to the temperature gradient.
• the lamellae consisted alternately of NiIn and Ni In EXAMPLE II
• the method described in Example I was used on an alloy of copper and indium (20.2 at. percent In, remainder copper, melting point approximately 700 C., eutectoid temperature 574 C.).
• the alloy was heated for two hours at 850 C. and subsequently coagulated by decreasing the temperature to 650 C.
• the grains of the alloy had a diameter of between 1 and 10 mms. after 2 hours of heating at 650 C. in the quartz tube.
• the external temperature gradient was 65 C.
• a lamella distance of .038 pm. was obtained at a passing rate of 0.16 cm. per hour and a lamella distance of 0.21 m. was obtained at a passing rate of 1.15 cm. per hour.
• the lamellae in the grains were parallel to the temperature gradient.
• the lamellae consisted alternatively of 29 at. percent In, remainder Cu and 11 at. percent In, remainder On.
• smaller grains approximately 50 am. it was found that the lamellae in the smaller grains were not directed parallel to the temperature gradient in contrast with the grains of more than 0.1 mm. in which this was the case (temperature gradient approximately 30 C. per cm., passing rate 0.5 cm. per hour).
• Example III The method described in Example I was used on an alloy of copper and aluminium (24 at. percent Al, remainder Cu, melting point 1100 C., eutectoid temperature 565 C.) which alloy was present in a tube of A1 The alloy was passed through a temperature gradient immediately after coagulation. The grain diameter was between 0.5 and 1 mm. The temperature gradient was 100150 C. per cm. At a passing rate of 0.2 cm. per hour a lamella distance of 0.25 ,um. was obtained, and
• Example IV The method described in Example I was used on an alloy of cobalt and silicon (25 at. percent Si, remainder Co, peritectic decomposition temperature 1219 C., eutectoid temperature 1170 C.). The temperature gradient was 300 C. per cm. At a rate of 0.05 cm. per hour the lamella distance was 1.4 ,um., at a rate of 6 cm. per hour the lamella distance was 0.4 ,urn. The lamellae were parallel to the temperature gradient. The grain diameter was between 0.5 and 3 mms.
• EMMPLE V The method according to Example I was used on a solid solution of tin in lead (16.6 at. percent Sn, remainder Pb). This solid solution is oversaturated at temperatures below 148 C.
• the grain diameter was between 0.5 and 1 mm., the temperature gradient was 100 C. per cm.
• a lamellar struc ture was obtained having a lamella distance of 0.9 pm, the lamellae were parallel to the temperature gradient.
• a method of producing a composite'of parallel oriented lamella shaped grains of two different metal phases comprising, heating an alloy capable of separating discontinuously into at least two phases upon cooling, to a temperature above the melting point of the alloy, cooling said melted alloy to a temperature between the melting point of the alloy and the eutectoid temperature of the alloy to thereby coagulate the molten alloy and form grains having minimum diameters of 0.1 mm. and then further cooling the resultant metal grains to room temperature by unidirectionally decreasing the temperature of said grains at a rate of at least 10 C. per cm. and not greater than the maximum rate at which the separation of said alloy into two or more phases occurs.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)

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• 1970
  • 1970-08-15 NL NL7012088A patent/NL7012088A/xx unknown
  • 1970-10-05 CA CA094758A patent/CA933450A/en not_active Expired
  • 1970-10-05 SE SE7013466A patent/SE375554B/xx unknown
  • 1970-10-06 GB GB4747970A patent/GB1333402A/en not_active Expired
  • 1970-10-06 CH CH1480470A patent/CH555411A/xx not_active IP Right Cessation
  • 1970-10-06 US US78575A patent/US3694193A/en not_active Expired - Lifetime
  • 1970-11-05 FR FR7039865A patent/FR2101317A5/fr not_active Expired

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