Fracture behavior and toughness of PST crystals of TiAl
Fracture behavior and toughness of PST crystals of TiAl
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DOI：
10.1016/1359-6454(95)00255-3
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发表时间：
1996-03
期刊：
影响因子：
9.4
通讯作者：
S. Yokoshima;M. Yamaguchi
中科院分区：
文献类型：
--
作者：
S. Yokoshima;M. Yamaguchi
通过缺口、疲劳预裂纹和侧槽试样的三点弯曲试验，研究了TiAl PST晶体的断裂行为和韧性。弯曲试验是在室温空气中进行的。TiAl PST晶体的缺口断口形貌和韧性强烈地依赖于其缺口相对于片层边界的取向和γ片层的晶体取向。在这项研究中，我们测试了具有五种不同缺口取向的试样，即I-110 <$、I-112 <$、II-110 <$、II-112 <$和III型，其中I、II和III分别是裂纹止裂器、裂纹分隔器和裂纹分层取向，并且11 hkl <$表示垂直于缺口平面的方向，该方向相对于γ层的晶体取向给出。试样的类型III失败的解理样模式上的宏观习惯平面平行于层状边界，并表现出非常低的断裂韧性值。类型I和II的试样具有相当粗糙的断裂表面和更高的断裂韧性比类型III。五个缺口方向的断裂韧性值依次增加：III、II-112 ° C、I-112 ° C、II-110 ° C、I-110 ° C。这些取向的断裂韧性和断裂面的微观结构特征的相对大小进行了讨论的结晶学和增韧机制PST晶体。
Fracture behavior and toughness of PST crystals of TiAl have been investigated through three-point bend tests of specimens which are notched, fatigue-precracked and side-grooved. Bend tests have been conducted in air at room temperature. Fracture surface morphology and toughness of notched PST crystals of TiAl strongly depend on their notch orientation with respect to the lamellar boundaries and crystal orientation of γ lamellae. In this study, we have tested specimens with five different notch orientations, i.e. types I-〈110〉, I-〈112〉, II-〈110〉, II-〈112〉 and III, where I, II and III are crack arrester, crack divider and crack delamination orientations, respectively, and 〈hkl〉 indicates the direction normal to the notch plane, which is given with respect to crystal orientation of γ lamellae. Specimens of type III failed by cleavage-like mode on a macroscopic habit plane parallel to the lamellar boundaries and exhibited a very low fracture toughness value. Specimens of types I and II exhibited considerably rougher fracture surfaces and much higher fracture toughness than type III. The five notch orientations give increasing fracture toughness values in the sequence: III, II-〈112〉, I-〈112〉, II-〈110〉, I-〈110〉. The relative magnitudes of fracture toughness and microstructural characteristics of fracture surfaces for these orientations are discussed in terms of crystallography and toughening mechanisms available in PST crystals.