Impression creep behavior of a cast MRI153 magnesium alloy

• Impression creep properties of MRI153 alloy was studied at 425–490 K.
• Pipe diffusion climb controlled creep is the dominant creep mechanism.
• Ca improves creep properties via dissolving in Mg17Al12 and forming Al2Ca phase.

Creep behavior of a cast MRI153 magnesium alloy was investigated using impression creep technique. The tests were carried out under constant punching stress in the range of 360–600 MPa at temperatures between 425 and 490 K. Microstructure of the alloy was composed of α(Mg) matrix phase besides Mg17Al12 and Al2Ca intermetallic compounds. Stress exponent of minimum creep rate, n, was found to vary between 6.45 and 7. Calculation of the activation energy showed a slight decrease with increasing stress such that the creep activation energy of 115.2 kJ/mol under σimp/G = 0.030 decreased to 99.5 kJ/mol under σimp/G = 0.040. The obtained stress exponent and activation energy data suggested that the pipe diffusion dislocation climb controlled creep as the dominant mechanism during the creep test.