Using the Monte Carlo method, the author examined the features of thermal cycling of pre-transitional low-stability structural-phase states of BCC alloys (using a traditional Copper-Zinc alloy and a Nickel-Aluminum (NiAl) intermetallic compound as examples) in various situations: during one or several thermal cycles, in the presence of complexes of planar defects (antiphase boundaries), and interactions between the complexes of thermal antiphase boundaries. Metal materials with a BCC structure are currently widely used because of their unique physical and mechanical properties. Copper and its alloys are traditionally widely used due to the combination of high mechanical and technological properties. Compared to copper, brass has higher strength, corrosion resistance, better casting properties, and a higher recrystallization temperature. A characteristic feature of alloys of the Ni–Al system is a high ordering energy. The NiAl intermetallic compound and solid substitutional solutions based on it have a high degree of long range order, which remains in the entire temperature-concentration region of their existence up to the melting point.