Особенности формирования структуры сплава Cu47Ni8Ti34Zr11 в условиях изотермической закалки из жидкого состояния

Abstract

RU: Методами согласованного численного решения уравнений теплопроводности и кинетики массовой кристаллизации выполнены расчеты параметров микроструктуры объемно–аморфизирующегося сплава Cu47Ni8Ti34Zr11 (Vit 101), образующейся при литье расплава в предварительно нагретую Cu–изложницу. На примере отливок сечением 0,5×10–3м показана возможность установления изотермического режима затвердевания и формирования первичных нанокристаллических структур.

EN: Problem statement. Production of metal materials with nanoscaled sizes of structural components relates to priority directions of a science and the up–to–date technologies. Progress in this field demands the deep understanding of interrelations of a chemical compound of alloys and technology factors with the physical properties setting a kinetics of crystallisation process. Effects theoretical and experimental researches of the noted interrelations will form a basis for developing and introduction in sphere of manufacture of special alloys of the new technological solutions providing a controllability by processes of structure formation and production of materials with predicted microstructures and properties that will promote the further development of micrometallurgy amorphous and nanocrystalline alloys.

Analyzing of the resent research. The quenching from a liquid state (QLS) is the up–to–date method of production of alloys with metastable crystalline and amorphous structures [7; 8; 12]. The probability formation of similar structures, besides a chemical compound and properties of a material, depends on a thermal mode of process.According to data of operations [3; 6], the basic versions of thermal mode QLS are:

- A mode of the continuous decrease in temperature of a melt up to the glass transition temperature which consequence is inhibition of crystallisation processes and material transition in an amorphous state;

- A mode including an initial stage of melt supercooling and a stage of a self–heating of the crystallizing volume following at the expense of the latent heat of transformation which promotes formation of polycrystalline structures with the microscale sizes of structural components.

Deficiency of the viewed modes is that with their help cannot be obtained nanocrystalline structures formed in the conditions of high–rate nucleation and extremely low growth rates of crystals.

Research objective. For the purpose of overcoming of this deficiency and expansion structure formation possibilities of technology QLS in references [5; 11] is offered the method of melt moulding in prior heated (hot) casting–form which allows to create the varied isothermal requirements of a solidification providing reception of a wide spectrum of structural states, including nanocrystalline. In the present, work results of the rated analysis of thermal modes and a crystallisation kinetics castings from easy amorphizing alloy Cu47Ni8Ti34Zr11 (Vit 101), gained by a rapid quenching in hot coppercasting–form are presented.

Conclusion. 1. On an example of alloy Vit 101 features of structure formation are explored at moulding in hot casting–form. Determined the interval of casting–form temperature values = (676 –674)K, which providing an establishment of an isothermal mode of a solidification castings, at temperatures on (5–93)K exceeding a glass transition point.

2. It is shown, that at an isothermal stage of process crystallisation is carried out with close to maximum ~(1015 — 1018) m–3×s–1 nucleation rates and very low ~ (10–13 — 10–8) m×s–1 rates of crystals growth, owing to what it is fixed completely crystallized structures with in the average crystal sizes from 63 to 240 nm.