High-Temperature Creep Mechanism of Two-Ductile-Phase Magnesium Alloy with LPSO-Phase

Masami Fujiwara 1, Hidenari Takagi 1 and Kenji Higashida 2

1 Division of Applied Physics, Department of General Education, College of Engineering, Nihon University
2 Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University

Abstract:

The high-temperature creep mechanism in an extruded magnesium alloy consisting of the α-Mg matrix and the long-period stacking ordered(LPSO) phase is investigated by performing theoretical analysis, indentation creep tests, and FE modeling. Creep behaviors of the two-ductile-phase alloy, which is expected to be a next-generation lightweight material, are theoretically predicted using the creep properties, the volume fractions, and the creep strength of the constituent phases. The stress exponent for creep is expressed by the harmonic mean value weighted with the effective volume fractions depending strongly on the creep rate. Experimental results suggest that the creep strength of the magnesium alloy with the LPSO phase almost satisfies the mixing rule and the isostrain-rate situation. Also, the stress exponent for creep varies with the creep rate and lies between the corresponding two values of the constituent phases in the power-law creep region. The same holds right for the activation energy for creep. Thus, creep characteristics of such two-ductile-phase alloy numerically represents the mechanical contribution of the reinforcing phase to the creep strength.