The alloy system Al-(Co)-Cr-Fe-Ni contains compositional ranges where a solid state BCC-FCC phase transformation leads to dual-phase materials composed of face-centered cubic (FCC) and body-centered cubic (BCC) phases with nearly equal volume fraction. The microstructure arising from this transformation at slow cooling rates is the classical Widmanstätten structure, with FCC-laths and colonies growing from grain boundaries into the parent BCC-B2 grain. Very distinct microstructures are obtained, when Widmanstätten growth is kinetically suppressed e.g., during continuous cooling with high cooling rates. These novel microstructures are associated with the spinodal decomposition of the parent BCC-B2 such that FCC growth occurs during the spinodal decomposition or upon annealing from a metastable, fully spinodal state. We review the microstructures at case as function of the imposed cooling regimes for the Co-free medium entropy alloy AlCrFe₂Ni₂. One of them, termed ultrafine vermicular microstructure, involves a characteristic and novel crystal orientation relationship (OR) between FCC and BCC. We identify the common planes and directions of this OR using electron backscatter diffraction maps to be {111}F⁢C⁢C∥{12⁢1¯}B⁢C⁢C and ⟨1¯01⟩F⁢C⁢C∥⟨1¯01¯⟩^BCC, respectively. Embedded is a second OR with {1⁢3¯⁢1¯}F⁢C⁢C∥{1¯⁢03}B⁢C⁢C and ⟨101⟩^FCC∥⟨010⟩^BCC. We further show that the vermicular FCC phase contains a high amount of lattice strain and sub-grain boundaries with disorientation angles in the range from 2 to 12°, as a result of the solid-state phase transformation.

合金体系Al-（Co）-Cr-Fe-Ni包含以下成分范围：固态BCC-FCC相变会导致由面心立方（FCC）和体心立方（BCC）相组成的双相材料具有几乎相等的体积分数。在缓慢的冷却速率下，这种转变产生的微观结构是经典的Widmanstätten结构，FCC条和菌落从晶界生长到母体BCC-B2晶粒。当Widmanstätten的生长在动力学上受到抑制时，例如在以高冷却速率连续冷却的过程中，可获得非常独特的微观结构。这些新颖的微结构与母体BCC-B2的旋节线分解有关，使得FCC的生长发生在旋节线分解期间或从亚稳的全旋节线态退火后。₂ Ni ₂。其中之一，被称为超细蠕虫微观结构，涉及FCC和BCC之间的特征性和新颖的晶体取向关系（OR）。我们使用电子背散射衍射图确定该OR的共同平面和方向为{111}F⁢C⁢C∥{12⁢1个¯}乙⁢C⁢C 和⟨1个¯01⟩F⁢C⁢C∥⟨1个¯01个¯⟩^乙CC， 分别。嵌入式是第二个OR{1个⁢3¯⁢1个¯}F⁢C⁢C∥{1个¯⁢03}乙⁢C⁢C 和⟨101⟩^FCC∥⟨010⟩^乙CC。我们还显示，由于固态相变，蠕虫状的FCC相包含大量晶格应变和亚晶粒边界，其取向角在2至12°的范围内。