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 brittlene ss, which results in a low K-Ic. A possible way to make aluminum MMCs tough er is to heat treat them. In this investigation the influence of three diff erent heat treatments on the K-Ic of AA6061 and AA6061 with 20 vol% Al2O3 i s investigated. Special attention is paid to the set of requirements needed to obtain a valid K-Ic 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 K-Q instead of K-Ic values. It prov es to be possible to obtain valid K-Ic data for the MMC using the standard disk-shaped compact tension geometry. The K-Ic of the MMC is around 21 MPa root m and the influence of the heat t reatments on the K-Ic seems to be very small. The reduction in K-Ic by the addition of 20 vol% Al2O3 particles to AA6061 is moderate, in view of the K -Ic of the matrix material, which on average is 27 MPa root m.