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Journal of Physical Studies 24(1), Article 1601 [7 pages] (2020)
DOI: https://doi.org/10.30970/jps.24.1601 INVESTIGATION OF THERMODYNAMIC STABILITY OF Fe–B ALLOYSN. Yu. Filonenko1, A. N. Galdina2
1State Institution ``Dnipropetrovsk Medical Academy of the Ministry of Health of Ukraine''
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It is known that processes occurring in a melt of binary alloys affect the crystallization process and the phase composition of alloys. To predict these processes it is necessary to determine the region of thermodynamic stability of the melt. The objective of this work is to study the structural properties of hypoeutectic and hypereutectic alloys in the Fe-B system, depending on the temperature of heating above the liquidus line and the aftercooling rate, as well as the thermodynamic properties of the liquid of Fe-B alloys. The research was carried out for the Fe-B alloys with boron content of 2.0-4.5\% (wt.), the rest is iron. To ascertain the effect of the overheating temperature and the aftercooling rate on the phase composition of alloys, the alloys were heated to 50-200 K above the liquidus line. Afterwards the melt was poured into a wedge-shaped mold and cooled with a rate of $10^2-10^4$ K/s. Microstructural and X-ray diffraction analyzes were used to determine the structural properties of alloys. It was established that the overheating of the melts up to 100 K above the liquidus line leads to formation of a finely divided eutectic structure and suppression of the formation of primary iron crystals in hypoeutectic alloys.
The increase in the temperature of overheating of the Fe-B melts to 150 K above the liquidus line leads to complete suppression of the formation of primary iron crystals in hypoeutectic alloys and partially -- to suppression of ${\rm Fe_2B}$ boride in hypereutectic alloys. It is shown for the first time that formation of ${\rm Fe_3B}$ boride occurs under heating to $100 $K above the liquidus line and aftercooling of hypoeutectic Fe-B alloys. Accounting in Gibbs energy for the first degree approximation of the high-temperature expansion of the thermodynamic potential for binary Fe-B alloy, we obtain for the first time the dependence of the temperature of the thermodynamic stability curve on boron content in alloy.
Comparison with experimental data showed a qualitative reproduction of these data. The nonmonotonе effect of the differential cross section dependence on the square of the transmitted four-momentum with increasing energy in the center of the mass system is described.
In the considered model, the nonmonotonе effect is a consequence of the proton spin properties. In our opinion, if we want to reproduce the quantitative experimental data, we will have to include the contributions from inelastic processes to the unitarity condition, but this requires a large amount of calculation.