The precipitation sequence in a QE22 Mg alloy is followed by differential scanning calorimetry, microhardness, electrical resistivity, positron annihilation spectroscopy and transmission electron microscopy (TEM) observations, after different thermal treatments. The decomposition of the supersaturated solid solution occurs via the formation of nanosized coherent structures (GP zones) followed by the co-precipitation of two metastable phases responsible for the peak ageing condition. The stable phase (Mg, Ag)12Nd appears at the highest annealing times, leading to over-ageing and hardness reduction. TEM observations provide information on the rystallographic structure of the forming phases, allowing some inconsistencies present in the literature to be clarified. Activation energies are derived from both calorimetric and resistometric measurements at different scanning rates.
PHASE TRANSFORMATIONS IN THE QE22 Mg ALLOY
FERRAGUT, RAFAEL OMAR;MOIA, FABIO;
2009-01-01
Abstract
The precipitation sequence in a QE22 Mg alloy is followed by differential scanning calorimetry, microhardness, electrical resistivity, positron annihilation spectroscopy and transmission electron microscopy (TEM) observations, after different thermal treatments. The decomposition of the supersaturated solid solution occurs via the formation of nanosized coherent structures (GP zones) followed by the co-precipitation of two metastable phases responsible for the peak ageing condition. The stable phase (Mg, Ag)12Nd appears at the highest annealing times, leading to over-ageing and hardness reduction. TEM observations provide information on the rystallographic structure of the forming phases, allowing some inconsistencies present in the literature to be clarified. Activation energies are derived from both calorimetric and resistometric measurements at different scanning rates.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
