Development of Widmansttten laths in a near- ? TiAl alloy
Development of Widmansttten laths in a near- ? TiAl alloy
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DOI：
10.1016/j.actamat.2005.04.007
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发表时间：
2005-08
期刊：
影响因子：
9.4
通讯作者：
S. Dey;A. Hazotte;E. Bouzy;Satoko Naka
中科院分区：
文献类型：
--
作者：
S. Dey;A. Hazotte;E. Bouzy;Satoko Naka
通过对四元近γ TiAl合金Ti-46.8Al-1.7Cr-1.8Nb（at. %）进行适度快速冷却，获得了由嵌入片层团中的Widmanstätten板条组成的显微组织。这些微结构的形态和晶体学特征，其特征在于使用SEM（EBSD）和TEM。不同的γ变体的识别是使用基于自动分析的原始方法完成的，所述自动分析是在会聚束模式下通过TEM获得的菊池图案。相对于嵌入的层状结构，魏氏板条系统地显示出围绕轴<$11 <$00 <$α 2的取向差为<$65 °。内部结构显示出与层状结构的相似性，即，γ相和α 2相之间存在Blackburn关系，γ惯习面为{111}多片晶结构。两种材料的显微硬度、α 2相的数量和形态也存在较大差异。此外，Widmanstätten板条包含大量的内部结构缺陷。根据上述结果，并考虑到魏氏板条和片层组织之间的65 °取向差与六方相（{112 23）的孪晶系统有关，我们提出了冷却过程中魏氏板条形成的一种新的转变机制。
Microstructures composed of Widmanstätten laths embedded in lamellar colonies were obtained by moderate rapid cooling of a quaternary near-γ TiAl alloy, Ti–46.8Al–1.7Cr–1.8Nb (at.%). The morphological and crystallographic features of these microstructures were characterized using SEM (with EBSD) and TEM. Identification of different γ variants was done using an original approach based on automatic analysis of Kikuchi patterns obtained by TEM in convergent beam mode. Widmanstätten laths systematically show misorientations of ∼65° around the axis 〈11¯00〉α2with respect to the embedding lamellar structure. The inner structure shows similarities with the lamellar structures, i.e., multi-platelet structure with Blackburn relationship between γ and α2phases and {111}γhabit planes. It also presents strong differences in terms of lamellae fineness and the amount and morphology of α2phase. Moreover, the Widmanstätten laths contain a lot of internal structure defects. From the results presented, and taking into account that the 65° misorientation between the Widmanstätten laths and the lamellar structures is associated with a twinning system of the hexagonal phase ({112¯2}〈1¯1¯23〉), we suggest a new transformation mechanism for the development of Widmanstätten laths during cooling.