Fe42.7Co39.6Cr8.6Ni9.1 高熵合金的微观组织和因瓦效应调控

Microstructural evolution and Invar effect of Fe_{42 7}Co_{39 6}Cr_{8 6} Ni₉. j high-entropy alloy were investigated. After 50 % cold rolling, alloy was annealed at 800, 900 and 1 000 °C. Microstructures were characterized using electron backscattered diffraction, while Invar effect was analyzed using dilatometer. Results indicate that FCC grain size generally increases with increasing annealing temperature and time; static recrystallization model is established and activation energy is determined to be 109. 5 kJ*mol ', which is similar to high-entropy alloys in the CoCrFeMnNi alloy System. During cooling after annealing, FCC—• BCC martensitic transformation takes place; nucleation and growth of BCC are affected by grain boundaries and other factors, so the evolution of BCC fraction with annealing condition is complicated. Additionally, Invar effect is confirmed between 27— 218 °C. It is because the spontaneous magnetostriction effect of ferromagnetic FCC phase counteracts with volume expansion partially caused by lattice Vibration. When BCC fraction increases from 5.6% to 25.2%, thermal expansion coefficient decreases from 3. 8 X 10 ' to 3. 3 X 10 °C . This indicates that thermal expansion coefficient only slightly changes; therefore, mechanical properties can be tuned through microstructural control while still keeping Invar effect.