Pope Andrew D, Chen Wen, Chen Hangman, Cao Penghui, Yeghishyan Armenuhi, Zhukovskyi Maksym, Manukyan Khachatur, Vohra Yogesh K
Department of Physics, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
Sci Rep. 2024 Jul 16;14(1):16472. doi: 10.1038/s41598-024-67422-x.
We report on the high-resolution imaging and molecular dynamics simulations of a 3D-printed eutectic high-entropy alloy (EHEA) NiCoFeCrAlW consisting of nanolamellar BCC and FCC phases. The direct lattice imaging of 3D-printed samples shows the Kurdjumov-Sachs (K-S) orientation relation {111} FCC parallel to {110} BCC planes in the dual-phase lamellae. Unlike traditional iron and steels, this alloy shows an irreversible BCC-to-FCC phase transformation under high pressures. The nanolamellar morphology is maintained after pressure cycling to 30 GPa, and nano-diffraction studies show both layers to be in the FCC phase. The chemical compositions of the dual-phase lamellae after pressure recovery remain unchanged, suggesting a diffusion-less BCC-FCC transformation in this EHEA. The lattice imaging of the pressure-recovered sample does not show any specific orientation relation between the two resulting FCC phases, indicating that many grain orientations are produced during the BCC-FCC phase transformation. Molecular dynamics simulations on phase transformation in a nanolamellar BCC/FCC in K-S orientation show that phase transformation from BCC to FCC is completed under high pressures, and the FCC phase is retained on decompression aided by the stable interfaces. Our work elucidates the irreversible phase transformation under static compression, providing an understanding of the orientation relationships in 3-D printed EHEA under high pressures.
我们报道了一种由纳米层状体心立方（BCC）和面心立方（FCC）相组成的3D打印共晶高熵合金（EHEA）NiCoFeCrAlW的高分辨率成像和分子动力学模拟。3D打印样品的直接晶格成像显示，在双相薄片中，面心立方相的{111}面平行于体心立方相的{110}面，呈现 Kurdjumov-Sachs（K-S）取向关系。与传统的铁和钢不同，这种合金在高压下会发生不可逆的体心立方相向面心立方相的转变。在压力循环至30 GPa后，纳米层状形态得以保持，纳米衍射研究表明两层均处于面心立方相。压力恢复后面双相薄片的化学成分保持不变，这表明该共晶高熵合金中发生了无扩散的体心立方-面心立方转变。压力恢复样品的晶格成像未显示两个最终面心立方相之间存在任何特定的取向关系，这表明在体心立方-面心立方相变过程中产生了许多晶粒取向。对处于K-S取向的纳米层状体心立方/面心立方结构进行的分子动力学模拟表明，在高压下体心立方相向面心立方相的转变完成，并且在稳定界面的辅助下，减压后面心立方相得以保留。我们的工作阐明了静态压缩下的不可逆相变，有助于理解高压下3D打印共晶高熵合金中的取向关系。
