Investigation of crack-tip plasticity in high volume fraction particulate metal matrix composites

Abstract

Crack-tip strain fields in high volume fraction ceramic particle reinforced metal matrix composites are assessed using photoelastic measurements. It is shown that the size of the significant crack-tip plastic zones that form in these materials depends on the type and diameter of the reinforcement and on the matrix material. This plastic zone size correlates well with the macroscopic toughness values assessed through J -integral testing. The composites are thus ''metallic'' in the sense that their toughness is mostly composed of plastic energy dissipation around the crack tip. Plastic deformation also induces marked constraint effects that influence the shape of the surface strain fields. It is shown that finite element analysis must be three-dimensional to describe these strain fields, as two-dimensional plane-stress analysis fails to reproduce the experimental data.

Fracture of aluminium reinforced with densely packed ceramic particles: influence of matrix hardening

“…The presence of extensive crack tip plasticity is deduced from the values taken by the ratio of toughness to yield stress of the composites. This is also demonstrated experimentally in a separate study, by revealing the crack-tip strain fields using reflective photoelasticity [42]. This feature creates a fundamental difference between the present composites and metal toughened ceramics (continuous ceramic, discontinuous metal) or interpenetrating phase composites (co-continuous metal and ceramic), both of which cannot exhibit macroscopic plasticity around a crack tip with a strong ceramic phase.…”

“…2(a)). It is therefore unlikely that large-scale yielding has occurred in such composites, as also confirmed experimentally in [42]. As a comparison, for tough unreinforced Al alloys for which large values of p are reported, tensile elongations are in the range of 10%.…”

Deformation rate effect on the microstructure and mechanical properties of Al–SiCp composites consolidated by hot extrusion

“…Some areas of applications in industries are aerospace, defense, automotive, sports applications, and marine. These are due to their attractive physical and mechanical properties including high strength, high stiffness, high thermal conductivity, high wear resistance and very good elevated temperature properties [4,5].…”

Increasing the Strength/Toughness Combination of High Volume Fraction Particulate Metal Matrix Composites using an Al‐Ag Matrix Alloy

“…The elevated toughness of these composites is achieved by meeting certain critical microstructural conditions, defined and explained in. [1][2][3][4] To summarize, these include: (i) the initial (high) quality of the stiff ceramic particles used, which must be free of stress concentration sites and internal defects, (ii) the presence of a ductile matrix free of brittle second phases, (iii) a capacity for composite bulk plastic deformation, made possible in spite of the high ceramic loadings by the fact that only the metal is continuous in their microstructure. These characteristics combined produce, in the composite, a local fracture cohesive law, [5,6] that features both (i) an elevated peak stress and (ii) a high local fracture energy.…”

“…[1] Traditionally, tungsten powders had to be fabricated through reduction of tungsten oxide minerals by hydrogen. [2,3] Once tungsten powders were fabricated, carburization of which was necessary to produce WC-Co powders. Carburization is…”