In Situ Measurements on Formation and Development of LPSO-like Nanostructures in Dilute MgYZn and MgGdZn Alloys

Precipitation process leading to the formation of long-period stacking ordered (LPSO) structures in dilute MgGdZn and MgYZn alloys during heating at a heating rate of 10 K/min have been examined by in situ synchrotron radiation small- and wide-angle scattering measurements. Samples were solution-treated and quenched prior to the measurements. During heating, two distinct temperature regions were observed for both alloys. The one at the lower temperature, clusters without in-plane order appeared, and then dissolved at higher temperatures. Clusters leading to LPSO structures appeared at a higher temperature above 600 K. Streaky peaks appeared above the temperature, suggesting that very thin layers of LPSO structure with relatively large domain size in the in-plane direction were formed. The average cluster-cluster distance in the segregation layer above 600 K was almost constant until dissolution of LPSO structure at 800 K. The average cluster-cluster distance is larger than the ideally ordered superstructures reported for stoichiometric LPSO alloys.