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Oriented Structure in Multicomponent Metallic Systems

#2794


Development of New Methods of Oriented Structure Obtaining in Multicomponent Metallic Systems

Tech Area / Field

  • MAT-SYN/Materials Synthesis and Processing/Materials
  • MAT-ALL/High Performance Metals and Alloys/Materials

Status
3 Approved without Funding

Registration date
20.06.2003

Leading Institute
Research and Production corporation "Magneton", Russia, Vladimir reg., Vladimir

Supporting institutes

  • VNIIKhT (Chemical Technology), Russia, Moscow\nMoscow State Technical University of Radioengineering, Electronics and Automation, Russia, Moscow

Collaborators

  • Centro Ricerche FIAT, Italy, Torino\nCNRS / Laboratoire de Magnétisme, France, Grenoble

Project summary

The objective of the project is the development of new techniques of aligned structure metallic specimens obtaining in Fe-Co-Cr-Mo, Fe-Co-Ni-Al-Cu-Ti systems by the solidification from the melt method.

Magnetic characteristics of the alloys will reach the following level:

Br, T HCB, kA/m (BH)max kJ/m5

UNDKT alloy 1.05 120 85

Fe-Co-Cr-Mo 1.5 70 75

Many problems of scientific and technical progress of developed industrial countries in priority technological fields are directly related to the development of new metallic materials and to the application of the crystalline anisotropy of these materials to the obtaining of maximum possible properties. Crystalline anisotropy in metallic materials ingots is achieved by directional controlled solidification technique in special apparatuses-crystallizers.

Metallic aligned ingots of metallic materials are currently widely used in the form of turbine blades, products with shape memory effects, etc.

Aligned metallic ingots are most stable to external effects – temperature, mechanical loads, aggressive media, etc.

Metallic aligned (single crystal) ingots are necessary to obtain precise physical characteristics of existing and newly developed metallic materials.

At the present time a well-known theory developed by a group of Canadian physicist (Chalmers, Tiller, Rutter, Jackson) [1, 2], based on the diffusion (concentration) undercooling principle is used to develop obtaining technique of aligned ingots of pure metals. This theory allowed to formulate the main principles of obtaining aligned crystals with the most perfect structure. To achieve this goal it is necessary to carry out crystallization process through a flat surface which is formed at the maximum temperature gradients in a liquid before the crystallization front and at minimum growth rates.

This theory is currently used for the development of obtaining technique of aligned materials both of pure metals with minimum impurity content and of multicomponent metallic systems. For all this it appears, that in spite of the creation of maximum possible temperature gradients and minimum growth rates the structure of these crystals is cellular or dendritic. It is often observed that growth rate increase leads to the formation of more perfect single crystal structure than when low growth rates are used. Also the effect of alloy components distribution coefficients and their concentrations on the aligned structure formation process is unknown.

In this work theoretical and experimental investigations of solid solution alloys crystallization will be conducted, relationship between the crystallization process and solidification will be determined, mechanism of single crystal structure formation in ingots depending on the alloy crystallization character and heat removal conditions will be studied, nonmetallic inclusions effect on “random” crystals nucleation before the crystallization front will be investigated.

The developed single crystal growth modes will allow to raise single crystal growth rate from 1 mm/min to 3-5 mm/min. For this, it is intended to conduct growing at moderate temperature gradients (60-80 deg./cm) through the two-phase zone. Such process will allow to avoid zone liquation formation and the dendritic liquation, being formed, will be easily eliminated by homogenization. The use of more efficient growth modes will allow to decrease the product cost by 30-40%.

During the implementation of the project it is supposed to use technical experience and methodology of every institute – the participant in the field of its main activities. In particular:

In JSC Research and Production Corporation “Magneton” great experience accumulated in the development process of single crystal ingots of magnetic materials of solid solution alloys and of alloys with eutectic and peritectic transformations will be used. Methods of metallographic, micro X-ray spectrum, X-ray, differential thermal analysis and electron microscopy will be used for investigations. These methods are usually used in MIREA and JSC “Magneton” during research work.

MIREA has great experience in the study of single crystal structure perfectness, of magnetic characteristics, analysis of fine crystal structure, in the determination of the gas composition in alloys.

The experience in achieving and investigating the properties of metallic alloys and single crystals, which has been accumulated in the organizations – the participants, gives confidence in successful solution of the formulated problem.

Expected results and their application

As a result of the Project implementation, physico-chemical bases of new obtaining methods of aligned structures of multicomponent metallic systems will be developed.

For the development of new Fe-Co-Cr-Mo, Fe-Co-Ni-Al-Cu-Ti system materials with a given reproducible complex of structure-sensitive properties and optimum microstructure solution of the following main problems is planned:


1. Development of preparatory obtaining methods of equilibrium multiphase specimens of Fe-Co-Ni-Al-Cu-Ti and Fe-Co-Cr-Mo system.
2. Comparison of obtaining process regularities of single crystal ingots of pure metals and of solid solution alloys with crystallization interval.
3. Determination of structure formation regularities depending on the crystallization character of solid solution alloys.
4. Obtaining of single crystal ingots by directional solidification technique.
5. Physico-chemical investigation of the obtained aligned structures.
6. Development of alteration methods of alloy crystallization character for the purpose of increasing the tendency to single crystal structure formation.
7. Investigation of monotectic, peritectic and eutectic reaction effect on the alloy tendency to single crystal structure formation.
8. Investigation of physical properties of aligned structures of Fe-Co-Ni-Al, Fe-Co-Cr-based alloys depending on the growth modes.
9. Obtaining of single crystals with the best characteristic parameters.

Depending on the place of the application, being planned, by this technique the following materials will be obtained:

- single crystal ingots with the diameter from 8 mm to 50 mm and the height 160-200 mm. Also single crystal ingots in the form of rectangles will be manufactured (manufacturing of ingots of more complex configuration is possible);

- single crystal ingots in the form of small size thin plates (1-3 mm high) manufactured form large size crystals by laser cutting technique along crystallographic directions (100), (010), (001). As a result, a flat surface which does not need further machining is formed.

The solution of the problems formulated in items 1-9 will permit to:

- manufacture on a commercial scale permanent magnets with columnar and single crystal structure of Fe-Co-Ni-Al-Cu-Ti based alloy with the operation properties by a factor of 1,5-2 high;

- to raise single crystal growth rate from 1 mm/min to 3-5 mm/min. It is supposed to carry out growing at moderate temperature gradients (60-80 deg./cm) through the two-phase zone;

- to decrease the product cost by 30-40%.

APPLICATIONS

- Fe-Co-Ni-Al-Cu-Ti and Fe-Co-Cr-Mo-Ti based alloys with columnar and single crystal structure – as permanent magnets;

- Nickel heat resistant alloys with crystallographic anisotropy – for the manufacture of gas turbine engine blades, shape memory effect products;

- Rod and rectangular bar shape magnets of single crystal ingots for the manufacture of more precise apparatuses of general commercial purpose (scales, seismosensors, etc.);

- Single crystal ingots are also necessary for the analysis of precise physical properties of metals and alloys;

- Application of large size single crystal ingots for the manufacture of small (1-3 mm high) permanent magnets for low current relays. It is convenient to manufacture such magnets by laser cutting thin plates along crystallographic directions (100), (010), (001). As a result a flat surface, which does not need further machining, is formed.

The project has following main stages:


1. Comparison of regularities of single crystal ingots obtaining process of pure metals and of solid solution alloys with crystallization interval.
2. Development of preparatory methods of equilibrium multiphase samples obtaining of Fe-Co-Ni-Al-Cu-Ti system.
3. Development of preparatory methods of Fe-Co-Cr-Mo system equilibrium multiphase samples obtaining. Selective sample synthesis for preliminary triangulation (partition) to particular more simple systems.
4. Determination of structure formation regularities depending on solid solution alloys crystallization character.
5. Construction of T-x-y-projections of the investigated systems. Determination of the liquidus surfaces form, crystal phase solidus surfaces form in T-x-y-space.
6. Investigation of multicomponent alloys crystallization character.
7. Obtaining of single crystal ingots by directional solidification technique.
8. Physicochemical investigations of the obtained aligned structures.
9. Investigation of the structure perfectness of Fe-Co-Ni-Al, Fe-Co-Cr based multicomponent alloys single crystals depending on kinetic growth modes.
10. Development of alteration methods of the alloy crystallization character for the purpose of increasing the tendency to single crystal formation.
11. Investigation of the monotectic, peritectic and eutectic reaction effect on the alloy tendency to the single crystal structure formation.
12. Investigation of the physical properties of the aligned structures of the alloys based on Fe-Co-Ni-Al, Fe-Co-Cr depending on the growth modes.

References

1. B.Chalmers. Solidification theory. M.Metallurgy. 1968. P.288.


2. M.Flemings. Solidification processes. M.World. 1977. P.424.


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