Volume 29, Issue 2 (March 2001)
A Critical Appraisal of Fracture Toughness Measurements on AA6061 and an Al2O3-Particle Reinforced AA6061 Alloy for Various Heat Treatments
A disadvantage of metal matrix composites (MMCs) is their assumed brittleness, which results in a low KIc. A possible way to make aluminum MMCs tougher is to heat treat them. In this investigation the influence of three different heat treatments on the KIc of AA6061 and AA6061 with 20 vol% Al2O3 is investigated. Special attention is paid to the set of requirements needed to obtain a valid KIc, as in some studies these are given little attention. In MMC material, the specimen geometry is governed by the delivered shape, which increases the risk of obtaining KQ instead of KIc values. It proves to be possible to obtain valid KIc data for the MMC using the standard disk-shaped compact tension geometry.
The KIc of the MMC is around 21 MPa √m and the influence of the heat treatments on the KIc seems to be very small. The reduction in KIc by the addition of 20 vol% Al2O3 particles to AA6061 is moderate, in view of the KIc of the matrix material, which on average is 27 MPa √m.