Formation and evolution of the hardening precipitates in a Mg-Y-Nd alloy

The formation and evolution of hardening precipitates in a Mg-Y-Nd (WE43) alloy during artificial ageing at 150 and 210 degrees C is followed by small angle X-ray scattering (SAXS) measurements, Vickers microhardness tests and transmission electron microscopy (TEM) observations. A quantitative description of the alloy studied during the early and advanced stages of the precipitation sequence is presented. In situ SAXS evolution at 210 degrees C of the size, volume fraction and number density of the subnanometer and nanometer particles that evolve in the beta '' phase was obtained. TEM and microhardness results indicate that the hardening mechanism is based on beta '' transformation of pre-precipitates and their growth at 150 degrees C, while at 210 degrees C hardening is mainly associated with beta '' -> beta' transformation. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.