Influence of Porosity on the Deformation and Fracture of Alloys

摘要

The tensile deformation and fracture behavior of alloys containing rounded porosity and with differing levels of matrix strain hardening has been examined both experimentally and analytically. The stress-strain response in uniaxial tension and, to a limited extent, plane-strain tension has been determined at room temperature for powder-fabricated titanium, and Titanium-6 Aluminum-4 Vanadium containing porosity. The strength and the ductility of both alloys decrease substantially with increasing porosity level. A large strain elastoplastic finite element model based on a regular array of equal-sized spherical voids is used to predict bulk porosity effects; the analysis is in good agreement with the experimentally observed rates of void growth, but it underestimates the degradation of strength with increasing porosity. In an analysis unique to P/M alloys, the effects of porosity on a local scale are examined successfully by a continuum imperfection model which predicts the fracture of porous materials with differing matrix strain-hardening characteristics. The analysis is significant in that it implies that a primary effect of porosity on fracture is to introduce into the material a network of planes of high local pore content (imperfections).