Re‐determination of the temperature of the coherent spinodal curve in an‐Al‐15 at.% Zn alloy by transmission electron microscopic and hardness investigations

Abstract

The character of the coarsening of the concentration modulations is studied in an AI-15 at. yo Zn alloy applying TEM investigations (TEM micrographs and diffraction patterns) and hardness measurements in the temperature range from 40 "C to 130 "C. From the TEM investigations the temperature of the coherent spinodal curve is estimated to be (93 f 7)OC. This value agrees fairly well with the result obtained by means of hardness measurements (kink in the TTT-curve occurring at about (84 f 3) "C). The TEM observations of structure revealed in the T,-range below the coherent spinodal a periodic structure relevant to spinodal decomposition. The periodicity of modulations is confirmed by electron diffraction patterns where a clear effect of sidebands near the matrix spots is observed. iiberein, der aus Hllrtemessungen (,,Knick" in der C-Kurve des TTT-Diagramms) erhalten wurde. Die TEM-Untersuchungen zeigen im untersuchten T,-Bereich ebenfalls periodische Strukturen, die auf spinodale Entmischung hinweisen. Die Periodizitiit der modulierten Struktur wird durch Beugungsaufnahmen bestatigt, die deutlich Seitenbander an den Matrixreflexen zeigen. Die Vergroberung der Konzentrationsmodulationen wird in einer AlZn