The role of the grain boundary in the fracture toughness of aluminum bicrystal

Complex interactions of defects such as dislocations and grain boundaries determine the deformation mechanism of nanocrystalline materials. Using molecular dynamics simulations, in this paper, we study crack propagation under mode I. Single crystals and bicrystals aluminum (Al) with different initial edge crack lengths were loaded until failure under controlled deformation. The effect of the grain boundary on the fracture toughness was analyzed. Tearing was observed and investigated in Al bicrystals. A novel methodology is proposed to estimate the fracture toughness in terms of J for Al single crystals and bicrystals. J was computed by means of three different methods, viz., J Contour Integral, Energy Release Rate, and Crack Tip Opening Displacement. Fracture toughness (J(C)) for bicrystal was 445% higher than for single crystal. J(C) for the single crystal was approximately 3 J/m(2) and 13 J/m(2) for the bicrystal. Comparison between first tearing in Al bicrystals and failure in single crystals was performed. Finally, it was evidenced that for Al bicrystals ductile fracture occurred during final fracture and the grain boundary had a large effect on the mechanical behavior of Al bicrystals.