LOCAL-ELECTRODE ATOM-PROBE TOMOGRAPHIC INVESTIGATION OF STRENGTHENING PRECIPITATES IN A Mg-7Zv-3Al ALLOY AT PEAK HARDNESS

摘要

The precipitates in the Mg-7Zn-3Al (in wt. %) alloy aged to peak hardness at 150°C have been characterized by local-electrode atom-probe (LEAP) tomography. The chemical compositions of the matrix and the precipitates were measured and compared with the results calculated using the COST2 database by the Thermo-Calc software. Ternary nanoscale precipitates have been found consistent with the predicted Φ phase demonstrating a metastable composition. The measured particle size at peak hardness, corresponding to an equivalent sphere radius of 17 nm, provides an important calibration point for quantitative modeling of precipitation strengthening for alloy design. The interfacial energy is also determined based on the capillarity effect.