Mechanical Property and Fracture Mechanism of Nanocrystalline Aluminum

  In this study, four groups of different process es of Ato+Ext, Ato+HIP+Ext, Cryo+Ext and Cryo+HIP+Ext were set to prepare bulk nanocrystalline/ultrafine-grained Al, and the mechanical properties of the bulks were determined. Then, tensile stress was analysized,the fracture morphology and corresponding dislocation morphology were observed respectively by scanning electron microscopy (SEM). Finally, the deformation and fracture mechanism were discussed. The result showed that the sample made with as-milled powder had an excellent strength compared to sample made with atomized powder. The indication of work hardening had not been observed in all tensile stress strain curves of the four samples. The dislocation movement, which could been seen obviously in ultrafine-grained samples, appeared only in large grain(≥100nm) in nanocrystalline samples. The tensile specimen of the bulk prepared via Ato+HIP+Ext exhibited a transcrystalline fracture, while intergranular fracture was happened to the other specimens.