The cyclic softening and evolution of microstructures for Mg–10Gd–2.0Y–0.46Zr alloy under low cycle fatigue at 573 K

As a candidate material for high temperature applications, the Mg–10Gd–2.0Y–0.46Zr alloy may undergo the alternate loading during the service lifetime. Under the total strain-controlled triangular waveform loading, the strength and the evolution of microstructures for the alloy at 573 K have been explored. The results show that the alloy presents cyclic softening characteristics at diverse total strain amplitudes. The grain boundary sliding has been detected near the cracks on the surface of the specimen, suggesting that the grain boundary sliding plays an important role in coordination deformation at 573 K. Microcracks initiate mostly either at grain boundaries for lower strain amplitudes or at persistent slip bands for higher strain amplitudes, and then propagate along grain boundaries. Due to twinning shear and the dislocations slip, the precipitates in the deformation twins disintegrate to form a small equilibrium phase. The dislocation cells, small angle grain boundaries, as well as dynamic recrystallization are observed in the precipitation-free zone.

► The Mg–10Gd–2.0Y–0.46Zr alloy exhibits cyclic softening characteristics at 573 K. ► Microcracks initiate mostly either at grain boundaries or at persistent slip bands. ► The precipitates in the deformation twins are smaller than that in the Mg matrix. ► Dynamic recrystallization appears in the precipitation-free zone.