Logarithmic divergence of the antiphase boundary width in Cu-Pd(17%)

Wetting of antiphase boundaries (APB) close to the order-disorder transition Tc is studied in the alloy Cu-Pd (17%) using dark-field transmission electron microscopy. Highly controlled heat treatments every 0.2 ^∘{}C just below Tc are performed and about 100 APB per temperature are examined. The observed temperature dependence of the APB is logarithmic. Because of the existence of a small two-phase region, a crossover between a wetting regime and a two-phase regime is expected, but a we show that in the logarithmic law remains valid up to less than 0.2 ^∘{}C below the lower critical temperature. From the logarithmic fit of the width the correlation length is found to be equal to 1.3 nm.