Derivation of the antiphase-boundary energy of L1 2 long-range-ordered precipitates from measurements of the minimum size of stable dislocation loops

In an alloy that is strengthened by long-range-ordered particles, a matrix dislocation generates an antiphase boundary (APB) when it cuts through such a particle. The specific energy n APB of this APB has been measured for two fcc alloys with spherical coherent L12 ordered particles: an Al-7.5at.%Li-alloy and the commercial Ni-base superalloy Nimonic PE16. Peak-aged specimens have been deformed and Orowan loops searched for using transmission electron microscopy. n APB has been derived from the radii of the smallest dislocation loops which have been left behind around particles. Such an approach had been used previously, for example, by Raynor and Silcock and by Nembach et al . Here an improved evaluation method has been applied; it is based on the results of computer simulations of the equilibrium configurations of dislocation loops.