The AlCrFe₂Ni₂ high entropy alloy exhibits an interesting microstructure, which changes considerably when various thermal treatments are applied. These changes are manifested mostly through the precipitation and dissolution of several BCC and FCC phases. To gain better understanding as to the phase evolution in AlCrFe₂Ni₂ with respect to the thermal history, the microstructures of four thermal states were investigated using Transmission Electron Microscope (TEM) and high resolution TEM. The thermal states included as-cast, homogenized at 1185°C for 75 min, homogenized and aged at 750°C for 4 h, and homogenized and aged at 930°C for 3 h. Common phases to all of the examined thermal states are Fe-rich FCC phase, ordered Ni-Al -rich BCC phase (B2), and disordered Cr-Fe -rich BCC phase. Following homogenization at 1185°C dissolution of the submicron-sized BCC phase particles in the ordered B2 phase was observed. Aging at 750°C resulted in the precipitation of nano-sized B2 platelets and needle-like particles inside the FCC phase domain, while the re-precipitation of nano-sized Cr-Fe globules occurred in the B2 phase. Aging at 930°C resulted mainly in the formation of submicron sized B2 platelets in the FCC phase domain.

AlCrFe ₂ Ni ₂高熵合金表现出令人感兴趣的微观结构，当进行各种热处理时，微观结构会发生很大变化。这些变化主要通过几个BCC和FCC相的沉淀和溶解来体现。为了更好地了解AlCrFe ₂ Ni _2中的相变关于热历史，使用透射电子显微镜（TEM）和高分辨率TEM研究了四种热态的微观结构。热态包括铸态，在1185°C下均质75分钟，在750°C下均质和老化4 h，以及在930°C下均质和老化3 h。所有检查到的热态的共有相是富铁的FCC相，有序的富Ni-Al的BCC相（B2）和无序的富铬铁的BCC相。在1185°C均质化后，观察到亚微米级BCC相颗粒在有序B2相中溶解。在750°C时效时，会在FCC相域内沉淀出纳米级B2血小板和针状颗粒，而纳米级Cr-Fe小球的再沉淀则发生在B2相中。