A simulation study of the shape of beta %26apos; precipitates in Mg-Y and Mg-Gd alloys

作者：Liu H; Gao Y; Liu J Z; Zhu Y M; Wang Y^*; Nie J F

来源：Acta Materialia, 2013, 61(2): 453-466.

DOI：10.1016/j.actamat.2012.09.044

• Magnesium alloys
• Precipitate shape
• First-principles calculation
• Phase-field method
• Alloy design

The metastable beta%26apos; phase is a key strengthening precipitate phase in a range of Mg-RE (RE: rare-earth elements) based alloys. The morphology of the beta%26apos; precipitates changes from a faceted and nearly equiaxed shape in Mg-Y alloys to a truncated lenticular shape in Mg-Gd alloys. In this work, we study effects of interfacial energy and coherency elastic strain energy on the morphology of beta%26apos; precipitates in binary Mg-Y and Mg-Gd alloys using a combination of first-principles calculations and phase-field simulations. Without any free-fitting parameters and using the first-principles calculations, CALPHAD databases and experimental characterizations as model inputs (lattice parameters of the beta%26apos; phase, elastic constants and chemical free energy of Mg matrix and interfacial energies of the coherent beta%26apos;/Mg matrix interfaces), the phase-field simulations predict equilibrium shapes of beta%26apos; precipitates of different sizes that agree well with experimental observations. Factors causing the difference in the equilibrium shape of beta%26apos;-Mg7Y and beta%26apos;-Mg7Gd precipitates are identified, and possible approaches to increase the aspect ratio of the beta%26apos; precipitates and thus to enhance the strength of Mg-RE alloys are discussed.

• 出版日期2013-1