Compressive creep behavior of the as-cast Mg–4Y‒xRE alloys

Abstract

Microstructural characteristics and high-temperature creep behavior of the Mg–4Y‒xRE (x = 1, 2, 3 wt%) (WE41, WE42, WE43) alloys were investigated by compressive creep testing at 523–598 K under the applied stresses in the range 75–275 MPa for dwell times up to 5400 s. The effects of increasing rare earth (RE) elements on creep resistance of the materials were studied and it was shown that WE43 has the highest creep resistance. Cuboidal phases of Mg24Y5 in all alloys and formation of eutectic structure of Mg-Mg12RE in WE42 and WE43 alloys with considerable thermal stability were responsible for enhancement of creep resistance of the tested alloys. Creep stress exponent values were in the range of 4.1–4.4, 4.0–4.4 and 4.0–4.6 for WE41, WE42, WE43, respectively. The respective activation energies were found to be 168, 169 and 173 kJ mol−1 for the WE41, WE42, WE43. The values of stress exponent and activation energies implied that dislocation creep was the dominant deformation mechanism, in which slip occurs by cross slip of dislocations.

Keywords

• WE magnesium alloys
• Compressive creep
• Creep mechanism