The dynamic tension behavior of an equiatomic CrCoNi medium entropy alloy (MEA) has been studied at both room temperature (RT, 298 K) and liquid nitrogen temperature (LNT, 77 K). Microstructural observations show that extensive phase transformations were activated in this alloy under dynamic tension at LNT instead of the activation of the deformation twins under high strain rate only or quasi-static loading at LNT. The appearance of massive nanoscale phase transformation bands along multiple slip directions even created a network structure of HCP lamellae in the FCC grains. This leads to defect accumulation at the intersection regions and results in the formation of new HCP variants, inverse phase transformations to FCC structure and even amorphous domains. Such transformation induced plasticity (TRIP) effects including the mutual interactions of crossover phase transformation bands on the plasticity and tension fracture of the MEA under extreme loading conditions were further discussed. These findings provide a deeper understanding of the deformation mechanisms in the equiatomic MEA under extreme loads.

中文翻译：

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等原子 CrCoNi 中熵合金在极端单轴拉伸下的广泛相变

研究了等原子 CrCoNi 中熵合金 (MEA) 在室温（RT，298 K）和液氮温度（LNT，77 K）下的动态拉伸行为。微观结构观察表明，该合金在 LNT 动态张力下激活了广泛的相变，而不是仅在高应变率或 LNT 准静态载荷下激活变形孪晶。沿多个滑移方向出现的大量纳米级相变带甚至在 FCC 晶粒中形成了 HCP 片层的网络结构。这会导致相交区域的缺陷积累，并导致形成新的 HCP 变体、向 FCC 结构甚至非晶域的逆相变。进一步讨论了这种相变诱导塑性（TRIP）效应，包括极端载荷条件下交叉相变带对 MEA 塑性和拉伸断裂的相互作用。这些发现让我们更深入地了解极端载荷下等原子 MEA 的变形机制。