Fracture behavior and toughness of NbSi2-based single crystals and MoSi2(C11b)/NbSi2(C40) duplex crystals with a single set of lamellae
Fracture behavior and toughness of NbSi2-based single crystals and MoSi2(C11b)/NbSi2(C40) duplex crystals with a single set of lamellae
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DOI：
10.1016/j.actamat.2011.03.040
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发表时间：
2011-06
期刊：
影响因子：
9.4
通讯作者：
K. Hagihara;T. Nakano
中科院分区：
文献类型：
--
作者：
K. Hagihara;T. Nakano
通过三点弯曲试验研究了(Mo0.85Nb0.15)Si2单晶的断裂行为和韧性。制备了两种不同微观结构的晶体，即C40单相单晶和具有取向单层的MoSi2(C11b)/NbSi2(C40)双晶，并比较了它们的断裂行为。双相组织改善了韧性，在几乎所有加载方向都表现出比C40单相单晶更高的值。双相试样A-2的断裂韧性提高了20%以上，其中片层边界平行于侧表面，缺口面平行于(1 2‘1 0)C40。由于裂纹扩展的显著偏转，A-2试件的断口出现了复杂的形貌。裂纹偏转主要发生在C40相中平行于{1 0 1‘0}解理面的平面上。C11b薄板有效地防止了裂纹沿缺口平面的初始快速扩展，因为它的位错容易滑动和它的变形能力有效地调节了应力集中。这会导致裂纹偏转，从而提高断裂韧性。
The fracture behavior and toughness of (Mo 0.85 Nb 0.15) Si 2 silicide crystals were investigated by three-point bending tests. Crystals with two different microstructures, namely the C40 single-phase single-crystalline form and MoSi 2 (C11 b)/NbSi 2 (C40) duplex crystals with an oriented single set of lamellae, were prepared, and their fracture behaviors were compared. The duplex microstructure improved the toughness, exhibiting higher values than the C40 single-phase single crystals at almost all loading orientations. An increase of more than 20% in the fracture toughness was obtained in a duplex specimen, A-2, in which the lamella boundaries are parallel to the side surface and have a notch face parallel to (1 2¯ 1 0) C 40. A complicated morphology appeared in the fracture surface of specimen A-2 as a result of significant deflection of crack propagation. Crack deflection occurred predominantly along the plane parallel to {1 0 1¯ 0} cleavage planes in the constituent C40 phase. The C11 b lamella effectively prevented the initial rapid propagation of cracks along the notched plane, because the ease of gliding of its dislocations and its deformability effectively accommodated stress concentration. This induced crack deflection, resulting in improved fracture toughness.