Study into the Effect of the Amount of the Strengthening Phase in an Aluminum-Based Dispersion-Hardened Composite on Fracture Regularities

Abstract

The results of studying the static tensile strength of aluminum-based dispersion-hardened composite materials with various contents of the Al₂O₃ strengthening phase are given. The materials under study are fabricated according to a new in principle technology based on burning out the aluminum melt when interacting with oxygen or an oxygen–nitrogen mixture. The fractographic patterns of the static fracture surfaces were studied for the samples fractured at maximal stresses. It is established that samples with a low Al₂O₃ content have a poorly viscous fracture pattern mainly consisting of a single fibrous zone. A radial zone appears in the fractograph with a twofold increase in the amount of the solid phase, while the alternation of viscous fracture, according to the detachment and shear mechanism with the manifestation of a brittle cleavage fracture signs, is observed with a threefold increase in the Al₂O₃ content. An analysis of fracture profilograms of the samples containing 10 and 30% inclusions of the solid phase reveals no abrupt drop in the surface relief, but an absolutely different fracture character is herewith found. However, in both cases, the form of profilograms is not pronounced by any abrupt relief jumps or extreme profile values, which makes it possible to affirm the stability of fracture processes. This is not true for the fracture of the sample with 20% Al₂O₃, in which a rather significant one-time drop is observed. The features of varying the fracture surface profile and distinctions over the arrangement place and number of crack nucleation regions in the samples under study are revealed using optical microscopy.