Dynamics of Crack Healing and Its Molecular Dynamics Simulation of Al2O3-MgAlON Composite

摘要

After preparing samples (3mm long×4mm wide×36mm high) of Al2O3-MgAlON composites and sintered at 1500°C for 2 h in N2 atmosphere,samples' cracks were carved by a Vickers hardometer's pressing head on the center of the sample surface (4 mm×36 mm).Subsequently,the cracks were healed at 1000°C-1550°C for 6 h respectively.Effects of healing temperature on sample's strength,crack healing dynamics and its molecular dynamics simulation were investigated.The results suggested that:the optimum range of cracks healing temperature was 1300°C-1550°C,and the healing process accelerated at 1300°C,meanwhile,the strength of samples increased significantly.Cracks completely healing finished at 1550°C.The dynamics equation of crack healing was lnv =-Q/kT+lnC.Through characterizing the crack healing rate with the recovering rate of sample's strength,the diffusion activation energy Q =4.264 × 10-30 J.K-1 and diffusion constant C=7.359 were claimed.The result of the molecular dynamics simulation suggested that cracks healing process was caused by diffusion could be divided into five stages:passivation of crack tips,formation of salient island,crack shrinkage,generation of secondary crack,and complete healing.