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Role of the X and n factors in ion-irradiation induced phase transformations of Mn+1AXn phases
Acta Materialia ( IF 8.3 ) Pub Date : 2017-11-04
Chenxu Wang, Tengfei Yang, Cameron L. Tracy, Jingren Xiao, Shaoshuai Liu, Yuan Fang, Zhanfeng Yan, Wei Ge, Jianming Xue, Jie Zhang, Jingyang Wang, Qing Huang, Rodney C. Ewing, Yugang Wang

Phase transitions induced in hcp Mn+1AXn phases (Ti2AlN, Ti2AlC, and Ti4AlN3) by 1 MeV Au+ ion irradiation were investigated, over a series of ion fluences ranging from 1×1014 to 2×1016 ions cm-2, by transmission electron microscopy (TEM) and synchrotron grazing incidence X-ray diffraction (GIXRD). Irradiation-induced structural evolutions were observed using high-resolution TEM (HRTEM) imaging and selected area electron diffraction (SAED). Based on phase contrast imaging and electron diffraction pattern (EDP) simulations, the atomic-scale mechanisms for the phase transitions were determined. Transformations of the initial hcp phases to the intermediate γ-phases and fcc phases were driven by the formation of Ti/Al antisite defects and extended stacking faults induced by ion irradiation. By comparing the transformation behavior of Ti2AlN with that of Ti2AlC and Ti4AlN3 under the same irradiation conditions, using both the experimental data and first-principles calculations, the role of the X and n parameters in the radiation responses of Mn+1AXn phases were elucidated. The susceptibilities of materials in this Ti-Al-X (X=C, N) system to irradiation-induced phase transitions were determined with respect to the bonding characteristics and compositions of these MAX phases. Ti2AlC is slightly less susceptible to the radiation-induced phase transformation than is Ti2AlN, which is attributed to the stronger Ti-Al bond covalency in Ti2AlN. Ti4AlN3 is more resistant to radiation-induced phase transformations than is Ti2AlN, due to the lower Al content and lower anion vacancy ratio in the irradiation-induced solid solution phases.



中文翻译:

X和n因子在离子辐射诱导的M n + 1 AX n相的相变中的作用

研究了1 MeV Au +离子辐照在hcp M n +1 AX n相(Ti 2 AlN,Ti 2 AlC和Ti 4 AlN 3)中引起的相变,其离子通量范围为1×10 14至20。 2×10 16离子cm -2,通过透射电子显微镜(TEM)和同步辐射掠入射X射线衍射(GIXRD)。使用高分辨率TEM(HRTEM)成像和选择区域电子衍射(SAED)观察了辐照引起的结构演变。基于相衬成像和电子衍射图(EDP)模拟,确定了相变的原子尺度机理。初始hcp相向中间γ相和fcc相的转变是由Ti / Al反位缺陷的形成和离子辐照引起的扩展堆垛层错驱动的。通过比较Ti 2 AlN与Ti 2 AlC和Ti 4 AlN 3的转变行为在相同的照射条件下,使用实验数据和第一性原理计算,阐明了X和n参数在M n + 1 AX n相的辐射响应中的作用。关于这些MAX相的结合特性和组成,确定了该Ti-Al-X(X = C,N)系统中材料对辐射诱导的相变的敏感性。的Ti 2 ALC是对辐射诱导的相变略小于敏感2的AlN,这归因于在钛更强的Ti-Al键共价2的AlN。Ti 4 AlN 3由于在辐射诱导的固溶体相中较低的Al含量和较低的阴离子空位比,因此与Ti 2 AlN相比,它对辐射诱导的相变具有更强的抵抗力。

更新日期:2017-11-10
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