Dual phase nano-particulate AlN composite — A kind of ceramics with high strength and ductility

Ceramics are widely used in many fields due to their excellent properties. However, the brittle fracture is a short board restricting their applications. To understand their deformation mechanism and explore a way to enhance both the strength and ductility, we investigated the mechanical behaviour of dual-phase AlNs composed of amorphous AlN matrix and crystalline nanoparticles under compression via molecular dynamics simulations. The stress concentration exists at the interface of nanocomposite AlN, where the particles and matrix are in the tensile and compressive states of stress, respectively. Strain hardening occurs when crystalline nanoparticle fraction f_v ≥ 40.9%, attributed to the intersection between shear bands. The phase transformation from wurtzite structure (B4) to graphene-like structure (GL) is observed in the crystalline phase, as a result of high hydrostatic stress. After phase transformation, the particle might be cut into half during further compression along with the recovery of the GL structure to the wurtzite structure that could still bear load. The investigation of the effects of the volume fraction, surface-to-volume ratio, distribution pattern of the crystalline nanoparticles indicates that the dual-phase AlN nanocomposite with f_v ≥ 40.9% and triangle distribution of particles would possess both higher strength and ductility.