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为了描述由纳晶基体和粗晶颗粒组成的纳晶双峰材料的断裂韧性,通过建立一个粘聚力模型来研究纳晶双峰材料的临界应力强度因子K_(IC)(表征材料断裂韧性)。考虑到纳晶双峰材料的一个典型情况:裂纹位于2个纳晶颗粒的交界面处,裂纹尖端与粗晶粒的晶界相交,假设粘聚区的尺寸等于纳晶颗粒的尺寸d。裂纹的钝化和扩展过程受位错和粘聚力的共同影响,刃型位错是从粘聚力裂纹的尖端发射,该过程对裂纹产生屏蔽效应。模型计算结果显示:当粗晶颗粒尺寸D确定时,K_(IC)随着纳晶材料晶粒尺寸d的增大而增大;当纳晶材料晶粒尺寸d确定时,K_(IC)随着粗晶材料晶粒尺寸D的增大而增大;相对于纳晶颗粒的尺寸,断裂韧性对粗晶晶粒的尺寸更加敏感。
In order to describe the fracture toughness of nanocrystalline bimodal materials composed of nanocrystalline matrix and coarse grains, a critical stress intensity factor (IC) (characterizing material fracture toughness) of nanocrystal bimodal material was investigated by establishing a cohesive model. . Considering a typical case of the nanocrystal material, the crack is located at the interface of two nanocrystalline particles and the crack tip intersects the grain boundary of the coarse grain, assuming that the size of the agglomeration zone is equal to the size d of the nanocrystalline grain. The passivation and propagation of cracks are jointly affected by dislocation and cohesion. Edge dislocations are emitted from the tip of the cohesive crack, which has a shielding effect on the crack. The results of the model calculation show that the K IC increases with the increase of the grain size d of the nanocrystalline material when the coarse grain size D is determined. With the determination of the grain size d of the nanocrystalline material, The coarse grain size increases with increasing grain size D; fracture toughness is more sensitive to the size of the coarse grain relative to the size of the nanocrystalline grains.