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The work is aimed at the development of a new sintered aluminium alloy with a low temperature coefficient of linear expansion that opens fundamentally new opportunities for solving the modern needs of domestic machinebuilding and instrument-making enterprises in light materials with special physical properties. Phase composition, structure and properties of cast aluminium alloys Al-Si-Ni with different contents of silicon and nickel, as well as powders obtained by grinding rapidly-quenched metal ribbons of these alloys in a high-energy ball mill are studied using various methods of structural analysis. The obtained values of the coefficient of linear expansion of the studied alloys in the cast state are significantly lower than those of pure aluminium, and they amount to = (11-15) 10-6 K-1. The method of obtaining a powder of a rapidly-crystallized alloy by manufacturing a rapidly-quenched metal ribbons using melt spinning followed by its dispersion in a high-energy ball mill is proposed for the fabrication of finely-dispersed powder and subse- quent hot pressing. [ABSTRACT FROM AUTHOR]

A technique of deformation heat processing for Al–Si based alloys is proposed which can significantly increase their both ductility and strength and also reveals additional reserves for their strength and hardness increasing through cold work hardening. The method includes serial of small hot plastic deformations with intermediate cooling and short annealing. This makes the silicon inclusion rather small with shape close to spherical, which leads to the ductility increasing. Then a work hardening processing could be performed for the material. Finally, both ductility and strength appear higher than in the initial cast state. [ABSTRACT FROM AUTHOR]

A mathematical physical based semi-empirical model and a corresponding computer program are developed for describing recrystallization process and carbonitrides particles precipitation in deformed austenite. The model is suitable for alloyed steels of a wide range of compositions. The model allows calculating a thermodynamic equilibrium for carbonitride excess phases with solid solution, the kinetics of their nucleation and growth, and their effect on recovery and recrystallization. A detailed description is given for each aspect of the model and its physical nature. Verification of the simulation results with the experimental data taken from published sources confirms the sufficient reliability of the proposed computer model for evaluative calculations. The model's features are demonstrated by an example that simulates influence of Nb content on recristallization, recovery and nucleation, growth and Ostwald ripping of Nb and Ti carbonitride particles. The simulation shows and numerically predicts the effect of slowing down recrystallization and recovery with increasing in Nb content. That attests significance of the effect of dispersed carbonitrides on recrystallization and recovery. The simulation theoretically predicts an intensification of Ti(C, N) particles precipitation and growth with an increase in the Nb concentration. As another result, it is an increasing the dispersion and number of Nb(C, N) particles with an increase in the Nb concentration owing to more rapid transition to the Ostwald ripening stage, which is characterized by much more slowly average particle size growth than from a supersaturated solid solution. [ABSTRACT FROM AUTHOR]

A mathematical physical-based semi-empirical model and a corresponding computer program are developed for describing recrystallization process and carbonitrides particles precipitation in deformed austenite. The model is suitable for alloyed steels of a wide range of compositions. The model allows calculate a thermodynamic equilibrium for excess carbonitride phases with solid solution, the kinetics of their nucleation and growth, and their effect on recovery and recrystallization. A detailed description is given for each aspect of the model and its physical nature. Verification of the simulation results with the experimental data from published sources confirms the sufficient reliability of the proposed computer model for evaluative calculations. The model's features are demonstrated by an example that simulates influence of Nb content on recristallization, recovery and nucleation, growth and Ostwald ripening of Nb and Ti carbonitride particles. The simulation shows and allows numerically evaluate the effect of slowing down recrystallization and recovery with increasing in Nb content. This indicates a significant effect of dispersed carbonitrides on recrystallization and recovery. The simulation theoretically predicts an intensification of Ti(C, N) particles precipitation and growth with an increase in the Nb concentration. Another result is an increase of dispersion and number of Nb(C, N) particles with an increase in the Nb concentration owing to more rapid transition to the Ostwald ripening stage, which is characterized by much more slowly average particle size growth than from a supersaturated solid solution. [ABSTRACT FROM AUTHOR]