Notch effects on deformation of crystalline and amorphous AlN – A nanoscale study

Aluminum nitrides (AlNs) have many unique properties for broad applications. However, their mechanical behaviour has not been well understood. In this work, the notch effects on the deformation of wurtzite AlN (w-AlN) and amorphous AlN (a-AlN) under tension were investigated using molecular dynamics simulations. As compared to w-AlN, lower strength sensitivity to the notch and the improved fracture toughness are observed in a-AlN, which are attributed to the short-range ordered atomic arrangement, rupture, reconstruction and rotation of bonds during deformation. The introduction of notch leads to obviously reduced strength and ductility in the w-AlN and a-AlN, respectively. The deformation in intact a-AlN is dominated by the formation of shear bands, followed by void coalescence. On the other hand, the deformation in notched a-AlN starts from the development of shear transformation zone near to the notches, followed by void coalescence. These results are useful in design of AlN based systems and devices.