Strengthening mechanisms of an Al-Mg-Sc-Zr alloy Original Research Article Pages 4165-4175

As a step toward developing an Al-Mg-Sc-Zr alloy for use up to 200 °C, the mechanisms responsible for alloy strengthening were identified for Al-6Mg-2Sc-1Zr (wt%) (Al-6.7Mg-1.2Sc-0.3Zr (at%)). The current work quantifies the active strengthening mechanisms at room temperature and explicitly considers solid solution strengthening, grain boundary strengthening, and Al3(Sc,Zr) precipitate strengthening. Existing strengthening models, together with data from microstructural characterization were used to determine the magnitude of individual contributions. Strengthening due to the sub-micron grain size was the largest contribution to alloy strength, followed in decreasing order by precipitate strengthening and solid solution strengthening. Tensile yield strengths, 540–640 MPa (78–93 ksi), measured at room temperature agree well with predicted values. Model predictions showed that increasing the precipitate size from 7.5 nm to 20–25 nm and increasing the volume fraction of these particles from 0.015–0.025 up to 0.035 could produce a material with a yield strength of 865 MPa (125 ksi).