镍基双晶体晶界断裂特性研究

对单晶体以及晶界平行晶粒裂纹和晶界垂直晶粒裂纹的双晶体的断韧性进行了实验研究，设计了三种三点弯曲试件，得到了单晶体和晶界的断裂韧性值，在晶界垂直晶粒裂纹的双晶体试验中，揭示了晶界对晶粒断裂的屏蔽效应；当裂纹距晶界某一特定长度时，断裂韧性值最大，理论分析和晶体滑移有限元数值分析揭示了这种屏蔽效应的机理，双晶晶界处的变表相容性导致了理解纹尖端应国和场的重新分布，并由此产生了晶界屏蔽效应。

The Grain Boundary fracture Behavior in Ni-base Bicrystals

The fracture behavior for Ni base bicrystals was studied by experiments. The fracture toughness for single and bicrystals of the metal was measured by three point bending test. The shielding effect from grain boundary was found in the test for grain cracked bicrystals with the crack normal to the grain boundary. It was also found that the fracture toughness exhibited a maximum value when the distance of crack tip from grain boundary reached a certain value. Based on theoretical analysis and with the help of numerical calculation, the mechanism for the grain boundary shielding effect was revealed.