Classifications

• • 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
  • C22C1/08—Alloys with open or closed pores
• • 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
  • C22C1/08—Alloys with open or closed pores
  • C22C1/083—Foaming process in molten metal other than by powder metallurgy

Definitions

• a process of manufacturing particle reinforced metal foam and product thereof A process of manufacturing particle reinforced metal foam and product thereof
• the present invention relates to a process of providing met foam and more particularly to a process resulting in provisi of thin wall close cell particle reinforced metal foam.
• foams There are several ways to produce foams. Different foaming tech niques are known such as incorporating hydrides in the molte metal or adding organic compounds which release gases on heat ing. Vapor deposition on polymeric substrates or casting o metal around granules which are then leached out leaving porous metal structure are other examples of providing metal with cellular structure.
• foams or ation using blowing agents are affecte by the surface tension and viscosity of the actual melt. Th viscosity counteracts bursting of the cell walls during a pro gressive increase in the volume of the formed bubbles, while low surface tension will favour formation of thin bubble walls.
• the properties of foams being gas-in-solid dispersions are largely determined by their density, but the cell size, struc ⁇ ture and their distribution are also important parameters in- fluencing the properties.
• foamed metals are produced by adding a gas evolving compound to the molten metal followed by heating of the resultant mixture to decompose the compound and to produce ex ⁇ panding cellulating gases.
• the foaming compound is usually metal hydride such as TiH 2 or ZrH 2 , and after the foaming step the mould is cooled to form a solid foam material. Cells of non- uniform structure and/or undesirably large size are experienced due to the difficulties with uniform distribution of the evolv ⁇ ing gas through the whole volume of the foamed metal.
• GB patent No. 1.287.994 discloses a process for preparation of metal foams applying a viscosity increasing agent comprising an inert gas or an oxygen containing material gaseous at the melt conditions and treating the thus produced viscous melt with a foaming agent.
• Air, nitrogen, carbon dioxide, argon and water are preferably used in the process as viscosity increasing agents in amounts from 1 to 6 grams per 100 grams of metal alloy.
• Metal hydrides are used as foaming agents (hafnium, titanium or zirconium hydrides) in amounts of from 0,5 to 1,0 grams per 100 grams of alloy.
• the increase in viscosity is enhanced by the presence of a promoter metal, e.g. from 4 to 7 weight% magnesium is used in aluminium alloys.
• a promoter metal e.g. from 4 to 7 weight% magnesium is used in aluminium alloys.
• a good mixing technique is required, the addition of foaming agents is usually carried out at a tempera ⁇ ture lower than addition of the viscosity increasing agent in a separate second vessel.
• the disclosed batchwise process, achiev ⁇ ing better foams with regard to uniform size and distribution of the cells, and claiming a certain reduction in the consumption of foaming agents, is a rather complicated time consuming and expensive process requiring several process steps and uni based on use of expensive heat decomposible gas evolving co pounds (hydrides) .
• European patent application No. 0 210 803 discloses a simil batchwise method of producing foamed metals based on use of fr 0,2 to 8,0 weight% metallic calcium as viscosity adjusting age and titanium hydride in amounts of from 1 to 3 weight% of t molten melt as foaming agent.
• Still another method of producing cellularized metal by decompo sition of a heat-decomposable gas evolving compound in molte metal is disclosed in US patent No. 3.297.431.
• the improvemen comprises addition of an intimately dispersed, finely divide powder to the metal prior to decomposition of the gas evolvin compound (carbonates or hydrides) , or dissolving of gas in th melt.
• the stabilizing powders may be metals or non-metals elements or compounds, and two wettable powders are preferen tially used where one of which forms a solid alloy with th metal.
• the gas is dissolved at one pressure and the evolved at a second lower pressure.
• a drawback in common for the hitherto known processes is tha all of them are batchwise operating processes using either ex pensive gas evolving compounds or dissolved gases as cellulatin means and viscosity increasing or stabilizing additives t achieve quality metal foams.
• Another object of the invention is to provide a method for up ⁇ grading of scrap metal material.
• Still another object of the invention is to provide a novel type of particle reinforced metal foam having improved mechanical properties.
• Fig. 1 shows schematically in the form of a flow-sheet the process of preparation of metal foam accord ⁇ ing to the invention.
• Fig. 2 displays a natural size contact print of the foamed metal sample prepared according to the invention
• Fig. 3 shows an optical metallograph picture of the closed cell Al-foam structure.
• Fig. 4 illustrates graphically results from a compres ⁇ sion test conducted on foam samples.
• a metal foam of the closed cell type structure having a uniform density and cell structure can be provided simply by feeding of finely dispersed cellulating gas into a molten particle reinforced metal matri composite material (PMMC) .
• PMMC metal matri composite material
• No special additives adjusting th viscosity of the melt or particular precautions with regard t the distribution of the cellulating gas bubbles through the mel were required.
• the gas bubbles rise to the top of the melt an form foam gradually increasing in volume.
• No tendency to burst ing of the foam cells when they reach the melt surface was ob served. This indicates a (highly) stabilized surface of the ga bubbles.
• the upper portion of the foam cake solidifies and ca be easily removed.
• Fig. 2 shows in natural size a photographic picture of th resultant foam sample removed as the solidified top part of th foam cake.
• the cross-section of the sample exhibits a unifor distribution of cells having a diameter in the range of from to 5 mm.
• the density of the sample was measured to 0,2 g/cm 3 .
• the achieved pores (cells) are essentially spherical and closed providing the foamed metal with isotropic properties in all directions, especially with regard to energy adsorption.
• Metallographic examination of the structure on the samples achieved from Example 1 reveals an extremely thin walled foam structure, as illustrated in Fig. 3.
• the wall thickness in this metallograph picture, magnification of 20, is in order of the reinforcing SiC particle size approximately 12 7 um.
• Fig. 4 The mechanical behaviour of the produced foam is represented in Fig. 4 illustrating the results from the testing of compressive stress conducted on the samples from Example 1.
• the achieved flat stress/strain curve from the samples having an initial height of 26 mm applying a crosshead velocity of 2 mm/min. is typical for this type of material as long as the cell structure did not collapse completely.
• the energy absorption of this foam was determined to be 2 kJ/1 foam, which is a very favourable value compared to the values reported in literature for commer ⁇ cially provided Al-foams.
• the achieved improved mechanical properties of the resultant foams are a result of a beneficial influence from the reinforcing particles incorporated in the cell walls.
• a a cellulating gas e.g. N 2 , Ar, C0 2 , He and even pressurized air which is normally easily available at low costs.
• the biggest potential of the presen invention is an up-grading of low grade composite scra material.
• This constantly increasing volume of composite scra today represents a considerable problem since it can not simpl be remelted or incorporated to the recycled secondary aluminium.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Powder Metallurgy (AREA)
• Laminated Bodies (AREA)
• Polyurethanes Or Polyureas (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (1)

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Cited By (19)

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Citations (4)

• 1989
  • 1989-07-17 NO NO892925A patent/NO172697C/no unknown
• 1990
  • 1990-07-11 HU HU9200169A patent/HU210524B/hu not_active IP Right Cessation
  • 1990-07-11 RU SU905011037A patent/RU2046151C1/ru not_active IP Right Cessation
  • 1990-07-11 DE DE90910522T patent/DE69006359T2/de not_active Ceased
  • 1990-07-11 CA CA002064099A patent/CA2064099A1/en not_active Abandoned
  • 1990-07-11 DK DK90910522.3T patent/DK0483184T3/da active
  • 1990-07-11 WO PCT/NO1990/000115 patent/WO1991001387A1/en active IP Right Grant
  • 1990-07-11 DE DE199090910522T patent/DE483184T1/de active Pending
  • 1990-07-11 BR BR909007549A patent/BR9007549A/pt not_active IP Right Cessation
  • 1990-07-11 ES ES90910522T patent/ES2049037T3/es not_active Expired - Lifetime
  • 1990-07-11 JP JP2510702A patent/JP2635817B2/ja not_active Expired - Fee Related
  • 1990-07-11 EP EP90910522A patent/EP0483184B1/de not_active Expired - Lifetime
  • 1990-07-11 AT AT90910522T patent/ATE100867T1/de not_active IP Right Cessation
  • 1990-07-11 KR KR1019920700095A patent/KR100186782B1/ko not_active IP Right Cessation

Patent Citations (4)

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