The hottest intermetallic compound heat treatment

2022-07-26
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The heat treatment process of intermetallics has been widely used.

intermetallics mainly refer to compounds with medium activity between metal elements and formed by metal elements and metalloids. There are stoichiometric components among elements, but their composition can change within a certain range to form a compound based solid solution. Intermetallics have become an important branch of new structural materials and have been widely used because of their excellent properties between metals and ceramics

1. Heat treatment method

the purpose of heat treatment is to obtain a certain ordered structure to improve its plasticity and toughness. There are mainly the following methods

(1) the as cast intermetallics under high temperature homogenization annealing generally have component segregation and casting stress. High temperature homogenization annealing is to eliminate the casting stress and further spread the alloy elements evenly, laying a good foundation for the next treatment. This treatment generally lasts more than ten hours above 1000 ℃

(2) in order to increase the room temperature toughness of intermetallics, they are often heated to the crystal transformation or phase transformation temperature, and then put into oil for quenching treatment. For example, the typical treatment process of Fe Al intermetallics is: heating to 1000 ℃, holding for 5h, and then putting into 700 ℃ oil for cooling. See references for details

(3) thermomechanical treatment is currently the most effective treatment method to significantly accelerate the exploration and development of domestic lithium resources in order to increase the toughness of intermetallics. It is mainly through forging, rolling, extrusion and other thermal deformation treatment to make its microstructure change in a direction conducive to increasing the toughness. See the literature for typical processes

The room temperature brittleness of

intermetallics has always been a problem that puzzles the application of this kind of materials. Due to different processing methods and changes in process parameters, the final microstructure and mechanical properties of alloys with the same composition may be very different. The thermomechanical treatment process is widely used in the preparation of intermetallics. By using this method, products with good combination of high strength and high plasticity that can not be achieved by general processing can be obtained

2. Development and application prospects in metal materials, intermetallics have been used as strengthening phase of metal matrix. People control the properties of matrix materials by changing the type, distribution, precipitation state and relative content of intermetallics. Because of its unique properties, intermetallics as a new kind of materials are being widely studied and developed. Because of their high temperature resistance and corrosion resistance, intermetallics have become important structural materials in many industrial sectors, such as aviation, aerospace, transportation, chemical industry, machinery and so on; Because of its special physical properties such as sound, light, electricity and magnetism, it can be used as semiconductor, magnetic, hydrogen storage, superconducting and other functional materials. In particular, the ordered intermetallics used as high-temperature structural materials have many good mechanical properties, oxidation resistance, corrosion resistance and high specific strength. Due to the long-range ordered arrangement of atoms and the coexistence of metal bonds and covalent bonds between atoms, it is possible that they have both the plasticity of metals and the high-temperature strength of ceramic household appliances and automobile related products that can not be painted or coated in time, so they have great application prospects

however, the brittleness of intermetallics hinders its application. Until the early 1980s, two breakthroughs were made in the toughening research of intermetallics. One is that hequanxiu and others from the Japanese Institute of materials science added 0.02% ~ 0.05% B to the brittle polycrystalline Ni3Al to toughen the material, and the tensile elongation at room temperature increased from nearly 0 to 40% ~ 50%; Second, the Oak Ridge National Laboratory found that in co3v with non plastic hexagonal D019 structure, Ni and Fe were used to replace part of CO, which could transform into face centered cubic L12 structure, and brittle materials into materials with good plasticity. These developments of oil-free bearings have enabled people to see the hope and Prospect of the new energy subsidy policy of intermetallics for landing high-temperature structural materials, and set off a research upsurge all over the world

at present, the ordered intermetallics as high-temperature structural materials are mainly the a3b and ab aluminides of Ni Al, Ti Al and Fe Al systems, which have been studied and made great progress at home and abroad

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