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通过TiAl基合金两种组织的四点弯曲断裂实验 ,研究了TiAl基合金的缺口断裂机制。实验结果表明 :缺口试样的断裂过程为几个沿层裂纹直接起裂于缺口根部 ,并沿着缺口根部的层间扩展 ;当遇到位向不利的晶粒时 ,裂纹便停止在这一晶粒前方 ,随着外加载荷的增加 ,即应力的增加 ,裂纹彼此连接并通过穿层裂纹而扩展 ;裂纹尖端超钝化、裂纹分叉、沿着层间偏转 ,形成显微裂纹区 ,裂纹停在障碍晶粒前的边界上为这种材料的韧化机制 ;裂纹扩展的驱动力是拉伸应力 ,缺口的存在增加了缺口前沿或者裂纹尖端的应力。
The fracture mechanism of TiAl-based alloy was studied by four-point bending test of two kinds of TiAl-based alloys. The experimental results show that the fracture process of the notched specimens is that the cracks along the layer crack directly at the root of the notch and extend along the gap at the root of the notch. When the unfavorable grain is encountered, the crack stops at this crystal In front of the grain, with the increase of applied load, ie, the increase of stress, the cracks are connected with each other and extended through the layer crack; the crack tip is hyperpassivified, the crack is bifurcated, the layer is deflected along the layer to form a micro-crack zone, The mechanism of toughening of this material is at the boundary before the obstructive grains; the driving force of crack propagation is tensile stress, and the presence of notches increases the stress at the notch front or crack tip.