全片层高Nb-TiAl合金损伤与断裂机理的研究

Damage and fracture mechanism of full lamellar high Nb-TiAl alloy

通过原位拉伸,分析试样表面与断口的SEM,对全片层高Nb-TiAl合金的断裂起始点、损伤行为、裂纹扩展及断裂机理进行研究。结果表明:材料呈沿层断裂和穿层断裂的混合形态,裂纹前端取向不利的层团附近出现大量微裂纹,当应力集中和外载荷共同作用时,引起微裂纹进一步贯穿。断裂机理为外载荷引起材料起裂和扩展,满足Griffiths断裂条件时,材料发生脆性解理断裂。起裂源一般出现在应力集中处,如缺口根部和材料薄弱处。

Based on the results of in-situ tensile and unloading testing,and SEM analysis of specimen surface and fracture surface,the in-situ tensile fracture initiation point,damage behaviors,crack propagation and fracture mechanism of full lamellar high Nb-TiAl alloy were studied. The results show that the fracture of the material presents a mixed morphology of interlamellar fracture and trans-lamellar fracture,and a large number of microcrack damage appear near the layer cluster with unfavorable orientation at the front of the crack. When the stress concentration is caused by the microcrack and the external load act together,the microcrack further expands. The fracture mechanism is analyzed as follows:brittle cleavage fracture occurs when the external load makes the initiation at the weak point and expand to a certain size to meet the Griffiths critical fracture conditions. The crack initiation site generally occurs at the geometric stress concentration of the material such as near the notch root and the weakest point of the microstructure when the material has no obvious stress concentration.