Tech Area / Field. MAT-ALL: Materials / High Performance Metals and Alloys

MAT-ALL: Materials / High Performance Metals and Alloys

MAN-MAT: Manufacturing Technology / Engineering Materials

PHY-STM: Physics / Structural Mechanics

Description of Technology
For the past of five years we have been studying the effects of excess pressures on crystal-melt phase transformation in metals. It has been a newly-discovered phenomenon: the extreme decrease of structure defects density of crystals grown from a melt under excess pressure of an inert gas in a crystallizer chamber. It has been found that, under optimal pressure values (depending upon the crystallographic orientation and the advance rate of crystal-melt interface), the impurity content and the dislocation density in the single crystals decrease greatly (by one and two orders of magnitude, respectively).

Theoretical analysis of experimental results allows us to assume that crystal-melt interface is able to become supermobile at the phase transformation and determines the conditions of the disappearance of thermodynamic and kinetic barriers for the interface motion in a condensed system. [Abstracts of the Tenth International Conference on Crystal Growth. (San-Diego, CA, USA), p. A154, p. D139 (1992)]. Also documented are the effects of excess pressure on dendritic morphology, the kinetic growth of crystals and pressure impulses during solidification of the melt on the grain sizes in an ingot and the cast structure of metal alloys. [Fizika Metallov i Metallovedenie, V.75, pp. 96-102 (1993)]. The results obtained point to a conclusion that low excess pressure is a parameter that permits effective control of the melt solidification process.

In the Crystal Growth Laboratory IMF, new methods were developed regulating solute concentration and structure defects density in single crystals grown from a melt for the effective refinement of materials, the growth of a single crystal, the regulation of dendritic structure alloys, the intensification of crystallization centers nucleation and the decrease of grain sizes in an ingot.

Legal Aspects
The experimental results of the use of the method of regulation of dendritic structure of monocrystals of alloys by application of excess pressure on the crystallizing melt was approved by US Laboratories; the report was included in a volume for perspective commercial customers. Patent applications have been approved in Russia for methods of effective control of metal materials structure by influence of excess pressure on the mobility of a crystal-melt interface.

Special Facilities in Use and Their Specifications
None.

Scientific Papers
V.O.Esin, "Supermobility of Crystal-Melt Interface," ICCG-10. Abstracts from the Tenth International Conference on Crystal Growth. (San-Diego, USA), A154 (1992).

V.O.Esin, A.S.Krivonosova, I.Zh.Sattybaev, T.G.Fedorova, "Extreme Decrease of the Dislocation Density of Al Crystals Grown from the Melt under Pressure," Ibid, D139.

V.O.Esin, A.S.Krivonosova, I.Zh.Sattybaev, T.G.Fedorova, "Effect of Low Excess Pressure Impulses during Melt Solidification on Aluminum Alloys Structure," The Physics of Metals and Metallography, Vol. 75, No. 5, pp. 531-535 (1993).

V.O.Esin, A.S.Krivonosova, I.Zh.Sattybaev, T.G.Fedorova, "Effect of Pressure on the Efficiency of Aluminum Refinement at the Directed Crystallization of Melt," Visokochistie Veschestva, No. 1, pp. 71-76 (1995).

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