Effect of Si on the creep properties of AZ61 cast magnesium alloy

• Si improves impression creep properties of AZ61 alloy.
• Creep of the alloys takes place via dislocation creep and Si has no influence on the mechanism.
• PLB is the dominant mechanism under high stress at high temperatures.

In the present study, the effect of silicon on the impression creep properties of AZ61 alloy was studied under different normalized stress values between 0.02 and 0.0425 at temperatures ranging from 423 to 495 K. The results showed that the steady state creep rate is decreased with increasing silicon content. The improvement of creep resistance of the alloy was ascribed to the formation of Mg2Si intermetallic phase having two Chinese script and polygonal morphologies. It was found that the stress exponent, n, varies between 4 and 7 for low stress values and between 10 and 14 for high stress levels. Creep activation energy values of 102–123 kJ/mol and 167–190 kJ/mol obtained for the low and high stress regimes, respectively. The obtained stress exponent and creep activation energies reveal that climb controlled dislocation creep and PLB are the dominant mechanisms under low and high stress values, respectively and Si has no influence on the dominant creep mechanism.

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