Features of Obtaining Multicomponent Magnetron Targets for the Formation of Non-Porous Transformation-Hardenable Coatings of a Given Composition

The technological process of thin-film sputtering significantly depends on the quality of the target for magnetron sputtering. This paper presents the features of obtaining the multicomponent magnetron target for the formation of non-porous transformation-hardenable coatings by the method of impact electric pulse consolidation. Special considerartion is given to the blend preparation and technological parameters of compaction. Blend powder consolidation under impact electric pulse compaction at different speeds of the striker has been investigated. At high speeds of the drop-hammer striker, the time parameters of the dynamic impact and electric pulse heating of the powder billet are shown to superpose, which leads to the final consolidation of the ceramic blend of the target for magnetron sputtering. The use of the technology of impact electric pulse compaction has made it possible to obtain multicomponent magnetron targets for formation of non-porous transformation-hardenable coatings of a given composition.

ELECTRIC PULSE HEATING OF REACTIVE COMPOSITIONS BY THIN-WALLED CONDUCTORS-HEATERS IN THE MODES OF MULTI-POINT IGNITION OF PROPELLANT CHARGES

The problem of electric pulse heating of a medium by the heater made of metal foil with an ideal thermal contact with the medium is solved. The solution is obtained in the form of rapidly converging series for ohmic heating power, which is given as an arbitrary function of time. Using the obtained solution, a dimensionless criterion is introduced for quasi-homogeneous heating of the heater up to a melting point with intensive heat transfer to environment. It is shown that with a fixed heating duration, the criterion value depends weakly on the type of a heating power function, which allows ignoring parameters of the external electrical circuit of the device while choosing the heater thickness. The definition of a "thin" heater is introduced, which admits of bulk droplet destruction during heating of a reactive medium. In the "thin" heater approximation, quadrature solutions to the thermal problem are obtained under heat exchange according to Newton's law and ideal thermal contact, when the heater power is an arbitrary function of time. Dimensionless similarity parameters of the simulated processes are identified in all solutions, which include thermal and physical characteristics of the heater and medium, as well as the thickness of the heater and the time of its heating up to the melting point. The applicability of the "thin" heater model for calculating the thermal state of a high-energy pyrotechnic coating is shown. As an example, the permissible values of the thickness of the magnesium foil heater are determined, which ensure its uniform heating up to the melting point in 1 and 5 milliseconds under the ideal thermal contact with ignited coating. The obtained quadrature solutions to the thermal problems and the calculated results are applicable in the design of compact electric pulse devices for contact multi-point ignition of various reactive compositions with efficient consumption of electric energy.

Direct observation of the processes near particle-to-particle contacts at electric pulse consolidation of titanium powder

Direct high-speed micro-video records prove the existence of highly overheated zones at the contacts of powder particles during short (~ 1 ms) electric current pulses. The value of overheating can exceed 1600 degrees and lead to the formation of liquid-phase sintering necks, the dimensions of which are well correlated with the size of the overheated zones. The micro-uniformity of the temperature field in the electric pulse heating allow understanding the unusually high consolidation rates of powder materials observed in spark plasma sintering.