Splat quenching

Last updated

Splat quenching is a metallurgical, metal morphing technique used for forming metals with a particular crystal structure by means of extremely rapid quenching, or cooling.

Contents

A typical technique for splat quenching involves casting molten metal by pouring it between two massive, cooled copper rollers that are constantly chilled by the circulation of water. These provide a near-instant quench because of the large surface area in close contact with the melt. The thin sheet formed has a low ratio of volume relative to the area used for cooling.

Products that are formed through this process have a crystal structure that is near-amorphous, or non-crystalline. They are commonly used for their valuable magnetic properties, specifically high magnetic permeability. This makes them useful for magnetic shielding and for low-loss transformer cores in electrical grids.

Procedure

The process of splat quenching involves rapid quenching or cooling of molten metal. A typical procedure for splat quenching involves pouring the molten metal between two cooled copper rollers that are circulated with water to transfer the heat away from the metal, causing it to almost instantaneously solidify. [1]

A more efficient splat quenching technique is Duwez's and Willen's gun technique. Their technique produces higher rates of cooling of the droplet of metal because the sample is propelled at high velocities and hits a quencher plate causing its surface area to increase which immediately solidifies the metal. This allows for a wider range of metals that can be quenched and be given amorphous-like features instead of the general iron alloy. [2]

Another technique involves the consecutive spraying of the molten metal onto a chemical vapor deposition surface. However, the layers do not fuse together as desired and this causes oxides to be contained in the structure and pores to form around the structure. Manufacturing companies take an interest in the resultant products because of their near-net shaping capabilities. [3]

Varying factors

Some varying factors in splat quenching are the drop size and velocity of the metal in ensuring the complete solidification of the metal. In cases where the volume of the drop is too large or the velocity is too slow, the metal will not solidify past equilibrium causing it to remelt. [4] Therefore, experiments are carried out to determine the precise volume and velocity of the droplet that will ensure complete solidification of a certain metal. [5] Intrinsic and extrinsic factors influencing the glass-forming ability of metallic alloys were analyzed and classified. [6] Another alternative process to generate non-equilibrium structures or metallic glasses is the melt spinning process. [7]

Product

Structure

The near-instantaneous quenching of the metal causes the metal to have a near-amorphous crystalline structure, which is very uncharacteristic of a typical crystal. This structure is very similar to liquids, and the only difference between liquids and amorphous solids is the high viscosity of the solid. Solids in general have a crystalline structure instead of an amorphous structure because the crystalline structure has a stronger binding energy. The way a solid can have the irregular spacing between its atoms is when a liquid is cooled below its melting temperature. The reason for this is the molecules do not have enough time to rearrange themselves in a crystalline structure, and therefore stay in the liquid-like structure. [8]

Magnetic property

Amorphous solids in general have a unique magnetic property because of their atomic disorder as explained above. They are rather soft metals and each has its own specific magnetic property depending on the means of production. In the splat quenching process, the metals are very soft and have superparamagnetic properties or shifting polarity behavior caused by the rapid and intense heat transfer. [9]

See also

Related Research Articles

Amorphous solid Non-crystalline solid

In condensed matter physics and materials science, an amorphous or non-crystalline solid is a solid that lacks the long-range order, which is a characteristic of a crystal. In some older articles and books, the term was used synonymously with glass. Today, however, "glassy solid" or "amorphous solid" is considered to be the overarching concept, and glass is considered to be a special case: glass is an amorphous solid maintained below its glass transition temperature. Polymers are often amorphous.

Crystal Solid material with highly ordered microscopic structure

A crystal or crystalline solid is a solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.

Glass Transparent non-crystalline solid material

Glass is a non-crystalline, often transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of the molten form; some glasses such as volcanic glass are naturally occurring. The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica, the primary constituent of sand. Soda-lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. The term glass, in popular usage, is often used to refer only to this type of material, although silica-free glasses often have desirable properties for applications in modern communications technology. Some objects, such as drinking glasses and eyeglasses, are so commonly made of silicate-based glass that they are simply called by the name of the material.

Ice Frozen water: the solid state of water

Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or 32 degrees Fahrenheit. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color.

Melting Material phase change

Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which increases the substance's temperature to the melting point. At the melting point, the ordering of ions or molecules in the solid breaks down to a less ordered state, and the solid "melts" to become a liquid.

Polypropylene Thermoplastic polymer

Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene.

Ingot Piece of relatively pure metal

An ingot is a piece of relatively pure material, usually metal, that is cast into a shape suitable for further processing. In steelmaking, it is the first step among semi-finished casting products. Ingots usually require a second procedure of shaping, such as cold/hot working, cutting, or milling to produce a useful final product. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods. Precious metal ingots can be used as currency, or as a currency reserve, as with gold bars.

Amorphous metal Solid metallic material with disordered atomic-scale structure

An amorphous metal is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most metals are crystalline in their solid state, which means they have a highly ordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity and they also display superconductivity at low temperatures.

Dendrite (metal)

A dendrite in metallurgy is a characteristic tree-like structure of crystals growing as molten metal solidifies, the shape produced by faster growth along energetically favourable crystallographic directions. This dendritic growth has large consequences in regard to material properties.

Amorphous ice is an amorphous solid form of water. Common ice is a crystalline material wherein the molecules are regularly arranged in a hexagonal lattice, whereas amorphous ice has a lack of long-range order in its molecular arrangement. Amorphous ice is produced either by rapid cooling of liquid water, or by compressing ordinary ice at low temperatures.

Peles tears Small pieces of solidified lava drops

Pele's tears are small pieces of solidified lava drops formed when airborne particles of molten material fuse into tearlike drops of volcanic glass. Pele's tears are jet black in color and are often found on one end of a strand of Pele's hair. Pele's tears is primarily a scientific term used by volcanologists.

Ceramic engineering Science and technology of creating objects from inorganic, non-metallic materials

Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties.

Spray forming, also known as spray casting, spray deposition and in-situ compaction, is a method of casting near net shape metal components with homogeneous microstructures via the deposition of semi-solid sprayed droplets onto a shaped substrate. In spray forming an alloy is melted, normally in an induction furnace, then the molten metal is slowly poured through a conical tundish into a small-bore ceramic nozzle. The molten metal exits the furnace as a thin free-falling stream and is broken up into droplets by an annular array of gas jets, and these droplets then proceed downwards, accelerated by the gas jets to impact onto a substrate. The process is arranged such that the droplets strike the substrate whilst in the semi-solid condition, this provides sufficient liquid fraction to 'stick' the solid fraction together. Deposition continues, gradually building up a spray formed billet of metal on the substrate.

Thermal spraying Coating process for applying heated materials to a surface

Thermal spraying techniques are coating processes in which melted materials are sprayed onto a surface. The "feedstock" is heated by electrical or chemical means.

Melt spinning

Melt spinning is a metal forming technique that is typically used to form thin ribbons of metal or alloys with a particular atomic structure.

Directional solidification

Directional solidification(DS) and progressive solidification are types of solidification within castings. Directional solidification is solidification that occurs from farthest end of the casting and works its way towards the sprue. Progressive solidification, also known as parallel solidification, is solidification that starts at the walls of the casting and progresses perpendicularly from that surface.

In materials science, paracrystalline materials are defined as having short- and medium-range ordering in their lattice but lacking crystal-like long-range ordering at least in one direction.

The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous materials from a hard and relatively brittle "glassy" state into a viscous or rubbery state as the temperature is increased. An amorphous solid that exhibits a glass transition is called a glass. The reverse transition, achieved by supercooling a viscous liquid into the glass state, is called vitrification.

Laser drilling is the process of creating thru-holes, referred to as “popped” holes or “percussion drilled” holes, by repeatedly pulsing focused laser energy on a material. The diameter of these holes can be as small as 0.002”. If larger holes are required, the laser is moved around the circumference of the “popped” hole until the desired diameter is created; this technique is called “trepanning”.

Crystallization of polymers is a process associated with partial alignment of their molecular chains. These chains fold together and form ordered regions called lamellae, which compose larger spheroidal structures named spherulites. Polymers can crystallize upon cooling from melting, mechanical stretching or solvent evaporation. Crystallization affects optical, mechanical, thermal and chemical properties of the polymer. The degree of crystallinity is estimated by different analytical methods and it typically ranges between 10 and 80%, with crystallized polymers often called "semi-crystalline". The properties of semi-crystalline polymers are determined not only by the degree of crystallinity, but also by the size and orientation of the molecular chains.

References

  1. Bennett, T.; Poulikakos D. (1993). "Splat-quench solidification: estimating the maximum spread of a droplet impacting a solid surface". Journal of Materials Science. 28 (4): 2025–2039. Bibcode:1993JMatS..28..963B. doi:10.1007/BF00400880. S2CID   119064426.
  2. Davies, H. A.; Hull J. B. (1976). "The formation, structure and crystallization of non-crystalline nickel produced by splat-quenching". Journal of Materials Science. 11 (2): 707–717. Bibcode:1976JMatS..11..215D. doi:10.1007/BF00551430. S2CID   137403190.
  3. Bennett, T.; Poulikakos D. (1993). "Splat-quench solidification: estimating the maximum spread of a droplet impacting a solid surface". Journal of Materials Science. 28 (4): 2025–2039. Bibcode:1993JMatS..28..963B. doi:10.1007/BF00400880. S2CID   119064426.
  4. Kang, B.; Waldvogel J.; Poulikakos D. (1995). "Remelting phenomena in the process of splat solidification". Journal of Materials Science. 30 (19): 4912–4925. Bibcode:1995JMatS..30.4912K. doi:10.1007/BF01154504. S2CID   136668771.
  5. Collings, E. W.; Markworth A. J.; McCoy J. K.; Saunders J. H. (1990). "Splat-quench solidification of freely falling liquid-metal drops by impact on a planar substrate". Journal of Materials Science. 25 (8): 3677–3682. Bibcode:1990JMatS..25.3677C. doi:10.1007/BF00575404. S2CID   135580444.
  6. D. V. Louzguine-Luzgin, D. B. Miracle, A. Inoue “Intrinsic and Extrinsic Factors Influencing the Glass-Forming Ability of Alloys” Advanced Engineering Materials, Vol. 10, N: 11, (2008) pp. 1008-1015. DOI: 10.1002/adem.200800134.
  7. Pagnola, M. R.; Barceló, F.; Useche, J. (2022-01-12). "Crack Formation in Chill Block Melt Spinning Solidification Process: A Comparative Analysis Using OpenFOAM®". JOM. 74 (4): 1477–1484. Bibcode:2022JOM....74.1477P. doi:10.1007/s11837-021-05105-y. ISSN   1047-4838.
  8. "Amorphous Solids" . Retrieved 12 November 2012.
  9. Rellinghaus, Bernd. "Magnetism in amorphous materials" . Retrieved 13 November 2012.