Fracture mechanisms in a high strain rate superplastic aluminum matrix composite

Tensile tests have been carried out at 713 similar to 843 K on a high strain rate superplastic Si(3)N(4)p/Al-Cu-Mg (2124) composite. The deformation characteristics are drastically changed by the presence of a liquid phase. In a solid state containing no liquid, cracks developed perpendicular to the tensile axis by plastic tearing because of the stress concentrations at the interfaces. However, no cracks were formed in a state containing a small volume of liquid, indicating that the stress concentrations are relaxed by the liquid phase. On the other hand, cracks were again formed in a state containing too much liquid. Thus, the presence of a liquid phase drastically changes the fracture mechanisms during high strain rate superplasticity for the composite.